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WATER SUPPLY 
AND 
DRAINAGE FOR 
BUILDINGS
CIB W062
44th INTERNATIONAL SYMPOSIUM 
AUGUST 28th - 30th 2018
PONTA DELGADA-AZORES . PORTUGAL
WATER SUPPLY 
AND 
DRAINAGE FOR 
BUILDINGS
CIB W062
44th INTERNATIONAL SYMPOSIUM 
AUGUST 28th - 30th 2018
PONTA DELGADA-AZORES . PORTUGAL
ISBN: 978-989-97476-2-3
Publication Date: 10th August, 2018
Title: Proceedings of 44th International Symposium CIB W062 on Water Supply and Drainage for Buildings
Organized by:
National Association for Quality in Building Installations (ANQIP), Portugal
Regional Laboratory of Civil Engineering (LREC), Azores (Portugal)
International Council for Research and Innovation in Building and Construction (CIB),
Commission W062 - Water Supply and Drainage for Buildings
Editors:
Prof. Armando B. Silva Afonso (University of Aveiro)
Doutora Carla Pimentel Rodrigues (ANQIP)
ANQIP – Associação Nacional para a Qualidade nas Instalações Prediais
Publisher:
ANQIP – Associação Nacional para a Qualidade nas Instalações Prediais
Disclaimer:
The organizers and the editors assume no responsibility whatsoever for the accuracy, completeness or 
usefulness of the information contained in these proceedings.
The authors alone are responsible for the contents of their papers.
5
2018 SYMPOSIUM CIB W062
 PONTA DELGADA-AZORES . PORTUGAL
The 44th International Symposium on Water Supply 
and Drainage for Buildings, CIB W062, is organized by 
the ANQIP (National Association for Quality in Building 
Installations) and the Regional Laboratory of Civil 
Engineering of the Azores (LREC), with the support of 
the International Council for Research and Innovation 
in Buildings and Construction (CIB). This Symposium 
will take place in Ponta Delgada, Azores (Portugal), from 
28th to 30th August 2018, and it is expected that, as in 
previous symposia, it will contribute significantly to the 
dissemination of research and innovation in the field of 
water supply and drainage for buildings.
The proceedings contain 45 papers, most of which 
were presented in eight technical sessions. This large 
number of communications has obliged the organizers 
to consider some presentations in the form of posters. 
Among other topics, the sessions cover research and 
development in “drainage and sanitation”, “water demand 
and supply”, “sustainability, rainwater harvesting and 
reuse of wastewater” and “water efficiency, water-energy 
nexus and sustainable construction”, including trends, 
applications, evaluation and management. We thank all 
authors for their participation and contributions to this 
symposium. 
We would further like to thank the international scientific 
committee and invited specialists for reviewing all the 
abstracts and papers and for their advice in editing the 
conference proceedings. We would also like to express 
our gratitude to the organizing committee and to all of 
our sponsors for their efforts and contributions toward the 
success of the event.
/ foreword
Armando SILVA AFONSO
44th CIB W062 Organizing Chairman
6
/ PARTNERS
Ordem dos Engenheiros
ERSAR
ADENE
/ INTERNATIONAL SCIENTIFIC COMMITTEE
L. Jack Coordinator of CIB W062, Heriot - Watt University, Scotland
A. Silva afonso University of Aveiro and Chairman of ANQIP, Portugal
B. Bleys Belgian Building Research Institute, Belgium
C. L. Cheng Taiwan University of Science and Technology, Taiwan
M. Nekrep University of Maribor, Slovenia
L. H. Oliveira University of São Paulo, Brazil
L. T. Wong Hong Kong Polytechnic University, China
M. S. O. Ilha University of Campinas, Brazil
O. M. Gonçalves Escola Politécnica University of São Paulo, Brazil
Z. Vranayova Technical University of Kosice, Slovakia
/ LOCAL ORGANIZING COMMITTEE 
Prof. Armando Silva Afonso: Professor Univ. Aveiro and Chairman of ANQIP
Eng. Francisco Fernandes: Diretor of LREC
Dr. Eng. Carla Rodrigues: Technical Diretor of ANQIP
Prof. Fernanda Rodrigues: Professora Univ. Aveiro
Prof. António Tadeu: Professor Univ. Coimbra
Solange Mouro: Secretary ANQIP
/ SPONSORS
Governo Regional dos Açores
Turismo do Açores
ALIAXIS
OLI - Sistemas Sanitários SA
Geberit
Grundfos
Sanitana
7
2018 SYMPOSIUM CIB W062
 PONTA DELGADA-AZORES . PORTUGAL
/ contents
A1 - Drain diameter reduction in a two-storey residential building drainage system for optimised performance to 
water conservation
Baroni, B.T., Oliveira L.H., Comas, F.N., Ota, I.R.
A2 - Principles of a genuine high flow waste water fitting with an in-pipe integrated ventilation
R. Weiss, A. Öngören
A3 - Reducing the Bioaerosol impact inner bathroom by air and damp exclusion
M.C. Lee, H.T. Tseng, H. Aota, A. Ikezawa, Y. Araki, M. Yamamoto, C.L. Cheng, W.J. Liao 
Page 10
Page 17
Page 25
A / Drainage and sanitation (I)
B1 - The Drainline Transfer of Solid Waste in Building Drains - Final Report
Peter DeMarco, John Koeller, P.E., Milt Burgess, P.E., FASPE, Matt Sigler, Charles White, Lee Clifton
B2 - Flow Characteristics and Seal Loss in Siphonic Waste Water Drainage System with Tail Trap
H. Miyata, K. Sakaue, T. Inada,T. Mitsunaga
B3 - Evaluation of the risk of Legionella spp. development in sanitary installations (part 2)
K. Dinne, O. Gerin, B. Bleys
B4 - Calculation for Evaporation Ratio of Trap Seal Water
K. Sakaue, T. Kojima
B5 - Consideration of same-floor drain as life-cycle maintenance solution in residential buildings
C.L. Cheng., C.J. Chen., W.J. Liao
Page 35
Page 42
Page 49
Page 55
Page 62
B / Drainage and sanitation (II)
C1 - User responses and hand washing times for faucets at supply water pressures 50−200 kPa
L.T. Wong, K. W. Mui, W. H. Cheung
C2 - Thermostatic Balancing Valves in Hot Water Circu-lation Systems
W.G. van der Schee, W.J.H. Scheffer
C3 - A survey on water consumption and unit design water supply amounts in office buildings
Y. Asakura, T. Nishikawa
C4 - Exploring cold and hot water consumption patterns in residential buildings
I. Meireles, B. Bleys, V. Sousa
C5 - The Calculating Methods for the Suitable Number of Fixtures Restroom of Highway Service Area
J.X. Zhang, K. Sakaue, G.Z. Wu
C6 - More codes and standards for DHW circulation systems: Fewer problems
JO.F. Leever
Page 69
Page 74
Page 80
Page 87
Page 94
Page 102
C / Water demand and supply (I)
8
/ contents
D1 - Design of Cascade Water Supply System for Ultra-high-rise Buildings
Eric W.M. Lee
D2 - Developing an algorithm for hot and cold water supply pipe design in medium-to-large scale residential 
buildings in the UK
S. A. Wickramasinghe, L. B. Jack, D.A. Kelly, A. Mylona, S. Patidar
D3 - The prediction method of supply water temperature for energy simulation of hot water supply system - 
Part2 Comparison between results of measurement and calculation of buildings in Kanagawa University
Shizuo Iwamoto, Ayano Dempoya, Kyosuke Sakaue 
D4 - Water Demand Calculator: Expected Material Cost and Energy Loss Reductions in Residential Dwellings
Daniel Cole, Steven Buchberger, Toritseju Omaghomi
D5 - Self-sufficiency-rate Prediction of Water Supplies Post Occurrence of Large-scale Earthquakes
K. Yagasaki, T. Nishikawa
Page 105
Page 112
Page 119
Page 128
Page 137
D / Water demand and supply (II)
E1 - Implementation of grey water reuse in the refurbishment of a flat: A case study
A. Silva-Afonso, C. Pimentel-Rodrigues, P. Carneiro, A. Jerónimo
E2 - Rain stock performance of rainwater harvesting equipment installed in an office building
Atsuya. Akasaka, Toyohiro. Nishikawa
E3 - Comparison of retention volumes of stormwater infiltration dry-wells determined using artificial neural 
network and heat flow analogy models
R. P.A. Reis, A. T. Ferreira, M. S. O. Ilha 
E4 - Integration of purification green wall system with grey water recycling in campus building
C.L. Cheng., J. R. Jhuo, C.H. Yeh.
E5 - Water Efficiency in Collective Non-Residential Buildings (Hotels)
D. Bermudez, R. Gomes, A. Silva-Afonso, C. Pimentel-Rodrigues, J. Gurierrez
Page 145
Page 152
Page 158
Page 168
Page 175
E / Sustainability, rainwater harvestingand reuse of wastewater
F1 - Defining the oversizing problem and finding an optimal design approach for water supply systems for 
non-residential buildings in the UK
S. Mohammed, L. B. Jack, S. Patidar, D.A. Kelly
F2 - Impact evaluation of low flow showerheads for bathing of Hong Kong: the water supply system design aspect
Y. Zhou, L.T. Wong, K.W. Mui
F3 - Evaluation of the impact from replacing ordinary by water-saving plumbing fixtures in water consumption
A. C. Alexandre, A. Kalbusch, E. Henning 
F4 - Energy to water nexus in domestic consumptions
Matos, C., Bentes, I., Cunha, A., Pereira, S., Faria, D., Gracio, J., Briga-Sá, A.
F5 - Water Efficiency Evaluation Model in Non - Residential Buildings. Case Study: University Buildings of Quito 
- Ecuador
C. Portilla, R. Gomes, A. Silva-Afonso, C. Pimentel-Rodrigues, F. Tobar
F6 - Re-imagine Your Street: A community engagement approach for improved urban resilience
D.A. Kelly, L. Alexander
Page 183
Page 192
Page 201
Page 208
Page 217
Page 228
F / Water efficiency, nexus water-energy and sustainable construction (I)
9
2018 SYMPOSIUM CIB W062
 PONTA DELGADA-AZORES . PORTUGAL
G1 - A study on a water-saving toilet with a splash-preventing function and the influence thereof on the drainage 
performance of high-rise drainage system
Shogo Sato, Masayuki Otsuka, Yuki Kuga, Takafumi Matsuo
G2 - Green walls and their retention efficiency
Z. Vranayova, D. Kaposztasova, J. Sabol
G3 - The applicability of multiple water-saving toilet units and a drainage system to upgrading toilets and 
drainage systems of office buildings
Masayuki Otsuka, Hayato Wakana, Saki Watari, Sadahiro Koshiba, Akihiro Doi 
G4 - Green infrastructure in interior according to TUKE students
Z. Poorova, Z. Vranayova
G5 - The energy efficiency of heat pump integrated with chilled water wall for air conditioning and domestic hot water
M. C. Jeffery. Lee, Christoph Mitterer, Y. M. Fang, Hartwig. M. Künzel
G6 - A study on the applicability of a water-saving toilet system for regular and emergency use along with the 
renovation of school toilets
Saki Watari, Masayuki Otsuka, Ryota Oba, Guangzheng Wu
Page 237
Page 246
Page 254
Page 267
Page 274
Page 281
G / Water efficiency, nexus water-energy and sustainable construction (II)
H1 - Inverted roof gravel tests
M.E. Buitenhuis
H2 - Assessment of BCP for plumbing systems of mid-size office buildings
T. Nishikawa, R. Yamazaki
H3 - Risk management in water supply networks: a case study
F. Rodrigues, M. Borges, Hugo Rodrigues 
H4 - User’s Behavior and Manners in a Water Park - Case Study in Katsushika and Edogawa City
H. Kose
H5 - Using UAS optical imagery to evaluate urban green areas
Matjaz Nekrep Perc, Hana Nekrep, Blanka Grajfoner
H6 - Research which Applies the Concept of BCP in a Company to the Concept of LCP in a Home in Japan
Tamio Nakano
Page 295
Page 302
Page 310
Page 321
Page 331
Page 340
H / Miscellaneous
I1 - A sustainable bathroom solution – the environmental performance of an off-site and modular constructed product
R. Pombo, I. Meireles, V. Sousa, M. Martín-Gamboa
I2 - Experimental analysis on energy and water consumptions at the domestic end use level: the particular case 
of showers
Briga-Sá, A., Faria, D., Silva, E., Pereira, S., Cunha, A., Matos, C.
I3 - Systems for the use of rainwater in buildings: the European standard EN 16941-1
M. Fernandes Caetano, H. Tavares da Silva, R. Ribeiro
Page 347
Page 354
Page 363
I / Posters
10
Drain diameter reduction in a two-storey residential building drainage 
system for optimised performance to water conservation
BARONI, B.T., OLIVEIRA L.H., COMAS, F.N., OTA, I.R.
A1/
Abstract
The increased demand for water, due to the population 
growth, has been an object of study of several researchers 
seeking ways to optimize the use of this resource. In this 
way, over the years the sanitary appliances have been 
improved to become more efficient. A concern is the 
impact on drains and main drains of building drainage 
system, once the water saving appliances demand less 
water in operation and so return smaller flow rates to the 
sanitary sewage network. Consequently, generate smaller 
waves that affect negatively on the self-cleaning horizontal 
pipes. In this sense, the aim of the article is to present the 
results of an investigation of the flow in drain and main 
drain of a two-storey residential building drainage system, 
in order to reduce diameters from 100 mm to 75 mm. The 
research was carried out in a vertical laboratory, where a 
typical residential bathroom in the upper floor was set up. 
A 6 L WC cistern and a 4.8 L WC cistern, a shower with a 
continuous flow rate of 0.20 L/s and a washbasin with a 
continuous flow rate of 0.15 L/s were used. The two WC 
cisterns were tested according to Brazilian Standard for 
calibration and both obtained satisfactory results in all 
the requirements of this standard, with exception of the 
discharge volume of the 4.8 L WC cistern. The diameters of 
the drain and main drain were varied from 100 mm to 75 
mm with and without the contribution of the continuous 
flow rate of 0.35 L/s from a shower and a washbasin and 
the slope of 0% in the drains and 1% the main drain. The 
influence of the parameters like slope, discharge volume, 
presence or not of continuous flow rate and pipe diameter, 
on the water flow velocity was evaluated. It is concluded 
that the reduction of drain and main drain diameters and 
the reduction of the discharge volume from 6 L to 4.8 L 
have been contributed to the increase of the wave speed 
in the all length of the drain. For the main drain, the same 
was not observed during tests. 
Keywords
Building drainage system; diameter reduction; drain; main 
drain; water conservation.
1 / Introduction
The water conservation provides a direct impact in 
the water supply and buildings drainage systems, as it 
implies in reducing of flow rates in water systems and, 
consequently, in drainage systems. Considering the current 
methods of dimensioning, these new values of flow rate 
can reduce the performance of the drainage system, since 
it depends on the waves generated by the consecutive 
discharges of sanitary appliances for the process of self-
cleaning of horizontal pipes. For this reason, the effect of 
flow rate reductions and, in particular, in drains and main 
drains of drainage building systems must be understood 
and considered in the dimensioning of these systems.
Today, due to the complexity of the transient flow, 
drains and main drains are still dimensioned considering 
steady flow. However, to reduce water consumption, 
the lowest values of flow rate and duration of the use of 
the sanitary appliances make the chance of steady flow 
state increasingly inadequate. In view of the limitation of 
analytical approaches for dealing with the complex flow, it 
becomes essential to the assessment of the performance 
of the system whereas the real state, unsteady flow, 
through full-scale tests.
Therefore, the aim of the article is to present the results of 
an investigation of the flow in drains and main drains of 
a residential building drainage system with two floors, in 
order to reduce diameters from 100 mm to 75 mm.
2 / The flow inside the building drainage systems
The drainage system presents a more complex flow than 
the water system, because the drainage system involves 
water and air and with varying pressures. While in the 
stack, the flow is anullar, in drains and main drains, it 
occurs as a horizontal free surface flow. To maintain the 
balance of pressures inside the pipes it is necessary to vent 
the system.
The flow in the horizontal pipes is unsteady, in that the 
variable time depends on the randomness of using 
sanitary appliances, their discharge profiles and of the 
wave attenuation of any discharge along a horizontal pipe.
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2018 SYMPOSIUM CIB W062
 PONTA DELGADA-AZORES . PORTUGAL
DRAINAGE ANDSANITATION (I)
2.1 The impact of the low flush volume WC to reduce 
diameters of drains and main drains
The issue of employment of diameters less than 100 
mm is discussed since the 19th century, as presented by 
Landi (1993). It can be claimed that the researcher who 
investigated further drainage in horizontal pipes was Prof. 
John Swaffield. Among the publications on the topic it 
is important to highlight Swaffield and Gallowin (1985), 
Swaffield and Gallowin (1989), McDougall and Swaffield 
(2000 and 2003), Swaffield (2009), among other works on 
the subject.
Oliveira (1992) studied the possibility of diameters 
reduction using a characteristics method software, 
developed at the University of Herriot Watt. It was 
held several simulations varying diameters, slopes and 
considering the simultaneity of use of sanitary appliances.
According to McDougall and Swaffield (2003), the 
discharge volume reductions caused by the increase of 
water conservation in buildings will lead inevitably to 
increased maintenance costs, unless they are considered 
reductions of diameters of drains and main drains, i.e. 
horizontal pipes of drainage building systems.
Plumbing Efficiency Research Coalition (PERC, 2012, 
2016) conducted the latest research whose objective 
was to study the flow in main drains of drainage building 
systems. Considering that the reduction of the WC 
discharge volume and other sanitary appliances lead to 
a decrease the amount of liquids unloaded in horizontal 
pipes, it is necessary to understand how the systems 
operate and what are the key variables that influence your 
performance.
Recent study conducted in Brazil, presents a performance 
evaluation in field about the employ of 4.8 L and 6 L WC 
cistern. It was verified damages to the drainage system 
after the installation of low flush WC. However, it has not 
been possible to conclude if the damage was caused by 
the low flush or due to the WC design, which does not 
provide adequate wave in order to clean main drains 
(VALENCIO and GONÇALVES, 2016).
The characteristics of the Brazilian WC use are very 
different from American and European countries. The 
main differences are disposal of toilet paper in the 
drainage system and low slope. Therefore, it is necessary 
to evaluate the possibility of reducing diameters, mainly 
in the residential buildings drainage systems with two 
floors, which in general, present, small lengths for drains 
and main drains.
3 / Methodology
The research was carried out in a vertical laboratory, where 
a typical configuration of a residential bathroom in the 
second floor was set up, as presented in Figure 1. A 6 L WC 
cistern and a 4.8 L WC cistern, a shower with a continuous 
flow rate of 0.20 L/s and a washbasin with a continuous 
flowrate of 0.15 L/s were used. The flow of shower and 
washbasin was from a floor trap. 
The diameters of the drain and main drain were varied 
from 100 mm to 75 mm with and without the contribution 
of the continuous flowrate of 0.35 L/s from a shower and a 
washbasin and the slope of 0% in the drain, on the upper 
floor, and 1% the main drain. The reason why the slope is 
0% on drain is due to many times this situation is founded 
in the bathrooms of residential buildings.
The two WC cisterns were tested according to NBR15097 
(ABNT, 2011) for calibration and both obtained satisfactory 
results in all the requirements of this standard, except the 
discharge volume for the 4.8 LWC cistern, once it does not 
have a specific standard. Three tests were conducted for 
each slope and 100 mm and 75 mm diameter.
Fig. 1: Typical configuration of a residential bathroom in the upper floor.
It were used transparent PVC pipes and fittings in order 
to enable the visualization of the flow depths in different 
12
sections, which were measured by means of lifting liquid 
capacitive sensors. The sections investigated in this 
research are presented in Figure 2.
Fig. 2: Placement of sensors on studied typical configuration.
For the data acquisition system, it was used MX840B 
HBM’s QuantumX, which is a universal data acquisition 
system of 8-channel compact size with Plug and Measure 
technology, speeding up the change of settings studied. 
The software used for data acquisition was the Catman of 
HBM.
4 / Results and discussions
The results of the flow in the drainage configuration of a 
bathroom in the upper floor of a two-storey building are 
presented in this item. It was employed 6 L and 4.8 L WC 
cisterns; drain, stack and main drain diameters of 100 mm 
and 75 mm and the slopes of 0% on the upper floor and 
1% on the lower floor. On the upper floor, the sections 
considered critical are the S1 and S3, while at the lower 
floor are the S2 and S3 and, for this reason, they are focus 
of attention. 
Tab. 1: Test settings in the upper floor.
In Figures 3 to 6, it can be observed the flow depths 
curves after discharging WC cistern in a 100 mm drain 
and a washbasin and shower, together, in a 50 mm drain, 
respectively (Figure 2). Figures 3 and 4 show the flow 
curves of a 6 L and 4.8 L WC cistern in a 100 mm drain and 
Figures 5 and 6 presents the flow curves in a 75 mm drain. 
The slope is 0% in all settings. 
Figure 3 shows the flow depths curves in six sections in the 
upper floor considering the 6 L WC cistern discharge after 
the washbasin and shower continuous flow rate (0.35 L/s) 
have stabilized at WC cistern drain.
Fig. 3: Flow depth in all sections of a 100 mm diameter drain, slope 0% and 6 L WC 
cistern flushing, shower 0.20 L/s and wash basin 0.15 L/s.
In Figure 3, with the 0% slope, a backwater in the sensor 
S1 and S2 and a peak flow depth on the sensor S4, of 43 
mm, are observed. The S3 section is the first section where 
the overlap of 
Figure 4 shows the flow depths in the six sections 
monitored in the 100 mm drain, slope 0% and considering 
the flushing of 4.8 L WC cistern, after washbasin and the 
shower continuous flow rate of 0.35 L/s stabilization.
Figure Drain diameter WC flush volume Slope
Continuous flow rate 
of wash basin and 
shower 0.35 L/s
Average speed 
between 
S1 and S3 (m/s)
3 100 mm 6 L 0% Yes 0.46
4 100 mm 4.8L 0% Yes 0.57
5 75 mm 6 L 0% Yes 0.70
6 75 mm 4.8 L 0% Yes 0.74
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2018 SYMPOSIUM CIB W062
 PONTA DELGADA-AZORES . PORTUGAL
DRAINAGE AND SANITATION (I)
Fig. 4: Flow depth in all sections of 100 mm diameter drain, slope 0% and 4.8 L WC 
cistern flushing, shower 0.20 L/s and wash basin 0.15 L/s 
Figure 5 shows the flow depths in the six sections 75 mm 
drain in the upper floor, considering the 6 L WC cistern 
discharge, after discharging the washbasin and shower 
(0.35 L/s) have stabilized in the WC drain.
Fig. 5: Flow depth in all sections of 75 mm diameter drain, slope 0% and 6 L WC 
cistern flushing, shower 0.20 L/s and wash basin 0.15 L/s 
Figure 5 presents, due to the low slope, the backwater 
from the 6 L WC drain to the floor trap (washbasin + 
shower), after 6 L WC discharging. The increased flow 
depth, indicated by the sensor in section S5, evidences the 
backwater. The peak of the flow depth is 33 mm, lower 50% 
the diameter drain. Another point to be highlighted is that 
the slope of 0% influenced the occurrence of a peak flow in 
section S3, downstream of the discharge of washbasin and 
shower (0.35 L/s), effluent of floor trap.
Figure 6 shows the flow depth curves in six the sections of 
75 mm drain, on the upper floor, considering the discharge 
of a 4.8 L WC cistern, after discharging of the washbasin 
and shower (0.35 L/s) have stabilized at the WC drain.
Fig. 6: Flow depth in all sections of 75 mm diameter drain, slope 0% and 4.8 L WC 
cistern flushing, shower 0.20 L/s and wash basin 0.15 L/s 
Figure 6 shows a small backwater in sections S1 and S2 
sensors, due to the low slope, between the time 4 and 6 
seconds. The peak flow depth is 59 mm in section S2, the 
nearest4.8 WC cistern.
4.2 Flow analysis in the main drain sections 
The test conditions, presented in Figures 7 to 10, are 6 L 4.8 
L WC cistern, flow rate from shower and washbasin with 
0.35 L/s, main drain diameter of 100 mm and 75 mm and 
slope of 1%. In the Table 2 are the summary of the trials in 
different configuration.
Figure Drain diameter WC flush volume Slope
Continuous flow rate 
of wash basin and 
shower 0.35 L/s
Average speed 
between 
S2 and S3 (m/s)
7 100 mm 6 L 1% Yes 1.20
8 100 mm 4.8 L 1% Yes 1,78
9 75 mm 6 L 1% Yes 1.08
10 75 mm 4.8 L 1% Yes 1.11
Tab. 2: Test settings in the lower floor.
14
Figure 7 shows the flow depth curves in the six sections in 
the 100 mm main drain with slope of 1% considering the 
6 L WC discharge, shower plus washbasin (0.35 L/s). The 
sensor S1 registers the maximum depth flow, located 0.77 
m from the stack and with a peak flow of 50 mm. 
Fig. 7: Flow depth in all sections of 100 mm diameter main drain, slope 1% and 6 
L WC cistern flushing, shower 0.20 L/s, washbasin 0.15 L/s 
Figure 8 shows the flow depth curves in the six sections on 
the 100 mm main drain, slope 1%, whereas the effluents of 
4.8 L WC cistern and washbasin plus shower (0.35 L/s). The 
flow depth, recorded by the sensor S1, reaches the peak of 
37 mm, about 37% of the main drain diameter, with wave’s 
attenuation of 10% of the section in about 8 seconds.
Fig. 8: Flow depth in all sections of 100 mm diameter main drain, slope 1% and 4.8 
L WC cistern flushing, shower 0.20 L/s, wash basin 0.15 L/s 
Figure 9 shows the flow depth curves in the six sections 
of 75 mm main drain, slope of 1% with the contribution 
6 L WC cistern and the shower plus washbasin (0.35 L/s), 
from floor trap. The sensor S1 registered the maximum 
flow depth, 0.72 m from stack, with two peaks of 59 mm. 
However, the maximum flow depth can be considered of 
45 mm, which represents about 60% of the main drain 
diameter.
Fig. 9: Flow depth in all sections of 75 mm diameter main drain, slope 1% and 6 L 
WC cistern flushing, shower 0.20 L/s, wash basin 0.15 L/s 
Figure 10 presents the flow depth curves in six the sections 
of a 75 mm main drain, slope 1% and considering a 4.8 L 
WC cistern with the contribution of a washbasin and a 
shower with steady flow of 0.35 L/s. 
Fig. 10: Flow depth in all sections of 75 mm diameter main drain, slope 1% and 
4.8L WC cistern flushing, shower 0.20 L/s, wash basin 0.15 L/s 
5 / Final considerations
It is important to note that these analyses apply to the 
boundary conditions of a small bathroom of a two-storey 
residential building, where the drain and main drain are 
small enough for main criteria of horizontal pipes cleaning 
be function of the wave speed.
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2018 SYMPOSIUM CIB W062
 PONTA DELGADA-AZORES . PORTUGAL
DRAINAGE AND SANITATION (I)
Considering that in critical conditions of flow, i.e. with 
all sanitary appliances in operation, and even with the 
shower and washbasin with high flow rates, the average 
flow depth of water reached a little bit more than 50% of 
the diameter of 75 mm.
In general, for this bathroom studied, it is observed for 
drain, in the upper floor, that reducing the diameters of 100 
mm to 75 mm and the reduction of the discharge volume 
of 6 L to 4.8 L can be beneficial actions for increasing the 
speed flow. It can improve the performance of the flow, 
especially in the initial sections of the system, where there 
is large kinetic energy accumulated in fluids. 
For main drain, in the lower floor, the flow changing from 
vertical to horizontal direction causes great turbulence 
with the appearance of a hydraulic jump. For that reason, it 
has not been possible to realize during tests a correlation 
between reducing the diameters or reduction of WC 
discharge volume with increasing flow velocity.
Therefore, it can be said that there is the possibility of 
reducing the diameters from 100 mm to 75 mm for drains, 
stacks and main drains of residential buildings of two 
floors and small bathroom, so small length of pipes, as 
shown in this study. For this reason, it is important that this 
research can advance with the use of media in the tests 
and through field studies.
Acknowledgments
The authors would like to express their gratitude to Conselho 
Nacional de Desenvolvimento Científico e Tecnológico - 
CNPq - Brasil (442920/2014-8) and Fundação de Amparo à 
Pesquisa do Estado de São Paulo - FAPESP (2015/22589-1) 
for financial support on the development of impact of water 
conservation in the sizing of building drainage systems, for 
the undergraduate research scholarships.
6 / References
Anonymous, Norma Brasileira NBR 15097 Aparelhos 
sanitários de material cerâmico – Parte 1: Requisitos e 
métodos de ensaios. Associação Brasileira de Normas 
Técnicas, Rio de Janeiro, 2011.
Landi FR – A evolução histórica das instalações hidráulicas. 
BT/PCC/100. São Paulo, 1993. 
McDougall JA, Swaffield JA – Simulation of building 
drainage system operation under water conservation 
design criteria. Building Services Engineering Research 
Technology. 2000, v.21 p.41–52. 
McDougall JA, Swaffield JA – The influence of water 
conservation on drain sizing for building drainage systems. 
Building Services Engineering Research and Technology. 
2003, v.24, n.4, p. 229-243.
Plumbing Efficiency Research Coalition – PERC – The 
drainline transport of solid waste in buildings - Phase 
1. Report. November, 2012. Available in: <http://www.
plumbingefficiencyresearchcoalition.org/wpcontent/
uploads/2012/12/Drainline-Transport-Study-PhaseOne.
pdf> Accessed in: December 1st 2016.
Plumbing Efficiency Research Coalition – PERC – The 
drainline transport of solid waste in buildings - Phase 
2.1. Report. March, 2016. Available in: <http://www.
plumbingefficiencyresearchcoalition.org/wpcontent/
uploads/2016/04/PERC-2-0_2-1-FINAL.pdf> Accessed: 
December 1st 2016.
Swaffield JA – Dry drains: myth, reality or impediment 
to water conservation. Water Supply and Drainage for 
Buildings CIBW062 Symposium, Sep. 2009, Germany. 
Proceedings…Dusseldorf, 2009, p. 301-313.
Swaffield JA, Gallowin LS – Hydraulics horizontal pitched 
drains based on vertical stack to drain entry condition. 
Water Supply and Drainage for Buildings CIBW062 
Symposium, Apr. 1985, Tokyo. Proceedings…Tokyo, 1985, 
29 p.
Swaffield JA, Gallowin, LS – Multistorey building drainage 
network design an application of computer based 
unsteady partially filled pipe flow analysis. Building and 
Environment. Jan. 1989, v. 24, n.1, p 99-110.
Valencio IP, Gonçalves OM – Field evaluation of housing 
units with low flush toilet (4.8 l/flush) installed: water 
consumption monitoring and damage verification in the 
drainage system performance. Water Supply and Drainage 
for Buildings CIBW062 Symposium, 29th Aug – 1st Sep. 
2016, Slovakia. Proceedings… Kosice, 2016, p. 198-211.
16
Bruno Tavares Baroni holds a Master’s of 
Civil Engineering from Escola Politécnica of 
the University of São Paulo, Department of 
Construction Engineering. Her thesis is the 
issue of non-potable water in buildings.
Lúcia Helena de Oliveira is an associate 
professor at the Department of Construction 
Engineering of Escola Politécnica of the 
University of São Paulo, where she teaches and 
conducts research work on building services.
Fernanda Nogueira Comas is an undergraduate 
student of Civil Engineering of Escola 
Politécnica of University of São Paulo 
with scholarship granted by CNPq for the 
undergraduating research on impact of water 
conservation in the sizing of building drainage 
systems.
6 / Presentation of Author(s) 
Baroni, B.T. (1), Oliveira L.H. (2), Comas, F.N. (3),
Ota, I.R. (4)
(1) bruno.baroni@usp.br
(2) lucia.helena@usp.br
(3) fernanda.ncomas@gmail.com
(4) igor.ota@usp.br
(1) Master’s degree in Civil Engineering, Department Construction Engineering, 
University of São Paulo, Brazil
(2) AssociateProfessor, Department of Construction Engineering, University of 
São Paulo, Brazil 
(3, 4) Graduate Student, Department Construction Engineering, University of 
São Paulo Brazil
Igor Rossi Ota is an undergraduate student 
of Civil Engineering of Escola Politécnica 
of University of São Paulo with scholarship 
granted by CNPq for the undergraduating 
research on impact of water conservation in 
the sizing of building drainage systems.
17
2018 SYMPOSIUM CIB W062
 PONTA DELGADA-AZORES . PORTUGAL
DRAINAGE AND SANITATION (I)
Principles of a genuine high flow waste water fitting with an in-pipe 
integrated ventilation
R. WEISS, A. ÖNGÖREN
A2/
Abstract
The demand for high flow capacity wastewater drainage 
systems is very high for sanitary and construction industries 
despite the known fact that high flow in drainage systems 
can often be related to the self-emptying of traps if the 
flow is not constricted to a maximum critical value. On 
the other hand, emptied traps can mean severe health 
issues as has been observed in the industry in the past. 
The scope of this research is to develop a new, technically 
optimized product which fulfils the demands of sanitary 
and construction industries with substantial material and 
labor saving advantages but without compromises on the 
health and other market issues. 
The study has been carried out utilizing both virtual 
engineering (CFD) and experimental methods. The main 
functioning principles of the new product concept is 
described precisely emphasizing the scopes as well as 
the assumptions behind each feature in this paper. The 
descriptions are supported by CFD simulation results 
obtained under a range of working conditions. The 
simulations consider the multi-phase characteristics of the 
flow in such systems. The test results obtained in the Geberit 
tower are presented to show the advantages and limits 
of the new development as compared to other existing 
drainage systems. The results of a series of tests according 
to the European Standards display the applicability of the 
new concept in buildings without any malfunctioning. The 
new concept is validated by comparison of the results of 
these tests with the requirements of standards.
The new concept proves to accomplish an approximately 
38% increase in capacity for a drainage stack of dimension 
DN100. With such an increase the drainage system reaches 
to its physical limit. 
Keywords
Wastewater drainage; High-flow fitting; High-flow stack 
system
1 / Introduction
The number of high-rise buildings increases in the last 
decades worldwide rapidly as the technologies in building 
and construction industry advances. The architects, 
MEP planers and contractors need among others new 
wastewater drainage system concepts in planning such 
buildings since the very high competition in this industry 
demands cost saving compact systems which allow 
installations with substantially less space. Some available 
systems like single stack Sovent or ventilated double 
stack systems have provided reasonable solutions so far 
however any improvement of these systems will help 
the construction industry further to build technically and 
commercially better optimized buildings. 
Fig. 1: Typical stack system configurations.
The single stack, single stack ventilated and single stack 
Sovent systems are three of the mostly utilized systems in 
building drainage applications. Some of the typical stack 
system configurations are shown in Figure 1. The type of 
system is selected principally based on the building size, 
so that the capacity of the drainage is sufficient for the 
building under consideration. The seal water loss by the 
traps connected to the system is the limiting factor which 
determines the allowable capacity of a stack regardless 
of the type of selected system. A trap which according 
to Standard EN12056-2 must always contain seal water 
at least having a height of 50mm. It is supposed that 
such a trap can hold wastewater gases back from inside 
of buildings effectively. For this reason, every sanitary 
discharge equipment, i.e. washbasin, bathtub, water 
closet (WC) etc., must always possess a trap externally 
or internally integrated. It is a common practice that a 
stack flow capacity resulting in a 50mm seal water loss is 
considered to be the maximum allowable capacity for that 
stack system. 
The water level in the trap is reduced either by evaporation 
18
of water if the sanitary appliance connected to it has 
not been used for a long time or by the effect of under 
pressure generated due to flow disturbances in the 
drainage system. The reduction of water must never 
exceed a level causing a free passage in the trap so that 
the waste water gas can reach to the living areas of the 
building. As specified in the standard EN 12056-2, this limit 
is reached when the flowrate Qmax=4.0 ℓ/s is attained in a 
single stack configuration of stack pipe dimension DN100 
and connected to soil and waste pipes with 90° elbows. 
This flowrate increases to 5.2 ℓ/s in the same system with 
swept entry connections to the side branches (Fig.1b). 
The capacity is elevated to 7.3 ℓ/s in a ventilated single 
stack system with swept entry connections to the soil and 
waste pipes (Fig.1c). A more modern building application 
is a single stack system connected to soil and waste pipes 
with Sovent type fittings (Fig.1d). It is possible to attain 
a capacity as much as 8 ℓ/s with such a system without 
any necessity to implement a supplementary ventilation 
piping.
These values are of course different when different sizes 
of stacks are considered to be implemented. In this study 
the stack dimension DN100 is always referred as reference 
since it is one of the most commonly implemented stack 
dimension in the building drainage systems. In this paper, 
the functioning principals and the main characteristics 
of a newly developed fitting which raises the capacity 
of a single stack Sovent type system significantly, well 
over 8 ℓ/s, without any compromises on the geometrical 
constraints, e.g. the size of piping system.
2 / Design and Testing Approaches
The development of the new fitting has been realized 
utilizing both virtual engineering and experimental 
methods. Virtual engineering (Flow Simulation Method, 
CFD) is preferred especially for the study of new fitting 
design concepts since such methods allow rapid 
parametrical investigations. This technique is used for 
instance to simulate the flow in the vicinity of Sovent 
junction including the side branch entry to exploit the 
characteristics of flow activities which are closely related 
to trap seal loss. A good understanding of the dominant 
flow mechanisms is possible by visualizing the flow in this 
region by means of CFD without necessitating physical 
prototypes.
Experimental investigations are carried out mainly for the 
verification of the end design according to the standard 
requirements and development demands. The test 
results of the new design as installed on a representative 
drainage system are also compared with those of similar 
systems like ventilated single stack system to exhibit the 
superiority and the advantages of the new design.
2.1 Flow simulation method (CFD) for wastewater flows
A commercial general purpose computational fluid 
dynamics (CFD) program is used in this study to carry 
out simulations of flow in the newly designed fitting. The 
program principally solves the equations of motion for 
fluids, to obtain transient, three-dimensional solutions 
to multi-scale, multi-physics problem in this case. The 
turbulent and unsteady nature of drainage flow is 
considered in the set-up of simulations by including 
the corresponding physical and numerical models in 
the calculation process. In addition, the multi-phase 
characteristics of the wastewater in the partially filled 
drainagesystem containing a large amount of air in the 
piping are taken into consideration. This feature of the 
utilized simulation technique is particularly important 
because the dynamics of air flow plays an important role 
in emptying the traps. Setting the boundary conditions at 
the free surface is employed for this purpose. 
The CFD program uses the volume of fluid (VOF) method 
for numerical solution of the governing equations. 
The governing equations combines all the physical 
models needed for defining the drainage system flows. 
The numerical solution of these equations yields an 
approximate solution to the original problem however 
it covers all the main features of such flows precisely. 
Detailed information about the formulation and the 
solution procedure of the technique used in this study is 
provided in reference [9].
2.2 Experimental methods
The tests have been conducted in the high tower test stand 
19
2018 SYMPOSIUM CIB W062
 PONTA DELGADA-AZORES . PORTUGAL
DRAINAGE AND SANITATION (I)
of Geberit Labs, which allows the installation of a 24m high 
8 story stack composed of Sovent fittings and combined 
with soil and waste piping. The distance between the 
stories is 2.65m except the bottom story where the height 
increases to 3.31m. The main stack is made of DN100 size 
PE-pipe. A sketch displaying the overall configuration of 
the piping system in the test tower is given in Figure 2. In 
the tests of cases single stack 90° and swept entry joints 
the Sovent fittings indicated in Figure 2 are replaced with 
these joints in the same test stack. 
The water is supplied to the stack at as many locations as 
necessary starting from the top level towards the bottom 
to reach the required test flowrate. At each level the flow is 
supplied to the stack at a maximum rate of 2.5 ℓ/s. To reach 
a maximum test level of the stack, 12.5 ℓ/s, the water is fed 
to the system at the top 5 stories as indicated in Figure 2. 
The tests with the stack systems considered in this paper 
are carried out for flowrates of 4 and 12 ℓ/s. The water 
feeding is adjusted to the necessary flowrate at the lowest 
level to come up with these values. For testing the 4 ℓ/s 
cases the stack is fed at the 8th story by 2.5 and at the 7th 
story by 1.5 ℓ/s, respectively. For testing the 12 ℓ/s cases 
the stack is fed at the top 4 stories from 8th to 5th by 2.5 
and at the 4th story by 2.0 ℓ/s, respectively. 
The measurement of seal loss has been accomplished 
utilizing a series of instrumented traps mounted on the 
side branches along the main stack at each level of the 
test tower. The instrumented traps are expected to loose 
water under the effect of pressure transients ocurring in 
the stack and in the soil and wastewater piping branches 
in a similar way to those of real drainage systems. The flush 
water is fed directly into the side branch pipe without the 
help of any sanitary appliance however experience in 
previous studies have proven that this type of feeding 
is also capable of generating pressure transients in the 
pipings similar to the flushings of sanitary devices as long 
as the feeding possesses equivalent flow conditions. It is 
experienced in many Geberit lab tests that a 45 second 
stabilized water feeding by a pump to the stack resembles 
the actual loading of a stack closely. Such a feeding creates 
testing conditions similar to actual flushing situations. In 
fact, this type of loading can be considered even slightly 
stronger than the reality. The stabilization of water feeding 
is reached after a 15 seconds start-up. Combined with a 15 
seconds of start-up time at the beginning, a total duration 
of 60 seconds has been set for each case. The seal water 
loss is higher if the trap is exposed to a longer loading, i.e. 
a longer flushing time. Therefore, it is important to set not 
only the flow rate but also the duration time appropriately 
to obtain accurate seal loss results.
The pump of the tower is run up to the predetermined flow 
rate gradually and slowly enough so that an excessive seal 
loss due to start-up transients is prevented. By this quasi-
stationary method, it is aimed on one hand to reach the 
maximum possible seal loss level on the other to achieve a 
high reproducibility during the tests. The time dependent 
behavior of flushing devices is neglected in this study 
assuming in is assuming that their effects are minor as 
compared to stack transients.
Fig. 2: An overview of the test stand.
20
The free end of each trap is closed where an ultrasound 
distance meter, a water fill pipe and an air vent are 
mounted. Figure 3 shows a typical instrumented 
measurement trap. At the beginning of each test, the traps 
are filled automatically up to their reference water levels. 
The trap water level as detected by the ultrasound meter 
on each trap has been recorded on a portable computer 
at the end of the test period. By this way it is assumed that 
the flow conditions, which represent those of an actual 
drainage system in a building are created. 
Fig. 3: A typical instrumented trap to deter-mine the seal loss distribution along 
the stack.
3 / Results
The principals of designing a drainage system for a 
building are described in the related documents of 
international standards. European Standard EN 12056 
is one of them listing the design rules for Europe [1]. A 
number of tables are provided in this standard specifying 
for example the proper dimensioning of piping based 
on the size of the drainage system needed for a building 
under consideration. The application range of each type of 
stack system is clearly indicated as well in these tables. A 
couple of such information have already been mentioned 
above in Introduction. 
It is important here to mention that understanding the 
physics of flow mechanisms which restrict the capacity 
of stacks so that an optimized design of such systems 
totally of partially by optimizing the elements contained 
in these systems can be possible. It is expected to increase 
the capacity of a system without any need to upgrade 
the system to a larger dimension and without causing 
additional complexities through such optimizations.
3.1 Hydrodynamics of drainage stacks and fittings 
One of the main causes of water loss in the traps is 
excessive turbulence generated in the stack near the 
side branch junctions which causes dynamic pressure 
pulsations at the traps. Secondly, the pressure surges 
appearing as a result of rapid velocity changes in the stack 
caused by the interruptions of air flow at the side branch 
junctions and/or at the elbow extending the stack to the 
collector pipes are responsible for excessive seal losses, 
i.e. emptying the traps. In Figure 4, an example of such a 
flow event is illustrated for a swept entry joint in a single 
stack system and the corresponding flowrate changes in 
the stack are displayed as a proof of occurrence of pressure 
surge in such systems. Moreover, these surges are often 
augmented by resonance like acoustical pressure pulses 
which are triggered in the stack by the surges themselves. 
Fig. 4: A time series of photos displaying flow disturbances at the junction and the 
corresponding flowrate transients.
Such a coupled event worsens the effect of pressure 
surge on emptying the traps significantly. A waste water 
drainage system can be improved effectively if all of these 
influence factors are minimized. An advance from 90° joint 
to swept entry joint provides a notable improvement in 
21
2018 SYMPOSIUM CIB W062
 PONTA DELGADA-AZORES . PORTUGAL
DRAINAGE AND SANITATION (I)
the joint configuration hydraulically so that the maximum 
capacity of single stack DN100 system can be elevated 
from 4.0 to 5.2 ℓ/s. An addition of an adequate ventilation 
piping to a DN100 single stack system provides enough 
stabilization against pressure surges in the stackso that 
the maximum capacity of such a system can be increased 
from 4.0 to 7.3 ℓ/s [2-5]. 
3.2 Conventional Sovent fitting 
The Sovent fitting concept as it is originally introduced to 
the building industry attempts to improve the hydraulic 
configuration of the joint and to reduce the influence of 
pressure surge simultaneously in the stack system. This is 
achieved by bypassing the side branch joint by means of 
the special design of Sovent as displayed in Figure 5. This 
configuration prevents a strong interaction of the flows on 
the stack and the side branch sides with each 
other. The water flow from the side branch piping proceeds 
in the direction of the stack flow before meeting it in the 
joint area. The two water flows have the same directions 
as they join together therefore they do not brake each 
other hence do not cause any disturbances in this critical 
area which can be directly transmitted to the side branch 
[3]. Additionally, with a proper change the direction of 
flow from the side branch, less turbulence is generated 
and only a partial termination of air column in the stack 
is permitted. Besides, the consequence of these positive 
changes in stack flow results in weaker pressure surges 
in the system. The maximum capacity of a Sovent stack 
of DN100 can reach 8.0 ℓ/s as compared to 4.0 ℓ/s of a 
conventional single stack system. 
3.2 High-flow Sovent fitting 
The new high flow Sovent fitting concept is based on 
the genuine idea of combining the advantages of both 
ventilated and Sovent systems in one unit. It assumed 
that a system with a higher allowable capacity and with 
better economic advantages might emerge from the 
combination of the functioning principles of these two 
present systems. The new concept should then reduce 
the pressure surge levels as much as possible and to 
separate the highly turbulent zones of the stack from the 
side branches as far as possible. Such a combination of 
effects is expected to reduce the seal water loss, and hence 
emptying of traps, to a minimum. 
High-flow Sovent consists of two main parts as depicted in 
Figure 6. The first part (1) consists of a flow divider. The flow 
divider cuts the water film developing on the stack walls 
to form an open window on the outer side of the Sovent 
fitting as the water film approaches the first elbow of the 
fitting. The divider collects at the same time the film flow 
as a wall jet and guides it to the opposite side of the stack. 
Fig. 5: A typical conventional Sovent fitting configuration with bypass flow around 
the joint.
The swirl zone of the Sovent high-flow fitting possesses 
at the immediate downstream of the flow divider an 
asymmetric off-set which is designed to guide the wall 
jet tangentially to the side wall before it proceeds further 
in the downstream direction. A slight rotation is created 
in the flow also as a consequence of this guidance. The 
rotation helps to keep the flow attached on the fitting wall 
(see Figure 6 - Top view). The special asymmetric off-set 
should also be positioned properly in the vertical direction 
in such a way that any congestion of the stack flow is 
avoided at the location where the side branch flow yield 
into the stack flow. It is worthwhile to mention here that 
the air- water separated layers of rotating flow is generated 
by means of passive asymmetric modification of the fitting 
body without requiring some elaborate spiral guides to be 
implemented inside the fitting body, as offered by others 
in the building industry.
22
Fig. 6: The main parts and characteristics of the new Sovent high-flow fitting.
These chain of flow activities result in two separated layers 
of flow in the Sovent fitting. The water layer is collected 
to flow on the fitting walls as a rotating film whereas 
the air flows in a channel appearing in the centre of the 
fitting extending from inlet to the oulet. The air channel 
developing in the fitting is connected to the air channel 
naturally forming along the centre of the stack through 
the window created by the flow divider which is described 
above. Consequently, a continuous air channel along the 
whole stack system as if an invisible ventilation pipe is 
integrated in the centre of the stack system.
Furthermore, the rotating water film flow stays always 
in contact with the pipe wall which results in a constant 
and increased friction resistance. Besides, the water flow 
follows a longer streamline because of its rotational motion 
in the vertical direction so that an additional reduction in 
the terminal velocity is experienced. Both characteristics 
point out a hydrodynamic stabilisation of the stack flow.
In Figure 7, the special flow characteristics of the new 
Sovent high-flow fitting including the air channel flow is 
exhibited in comparison to two stacks, one consisting of 
a swept entry joint and the other a conventional Sovent 
fitting. In Figure 7(a), it is clearly observed that as the 
cylindrical film flow passes by the swept entry joint it is 
forced to totally collapse on the stack side opposite to the 
joint by the effect of side branch flow. This causes the air 
channel close and terminate at this location. A new film 
flow is started from this location on until it is terminated 
again at the same location by the next joint. Figure 7(b) 
displays the development of the cylindrical film flow from 
the stack pipe into a conventional Sovent fitting. In this 
case, the cylindrical film flow passing through the fitting 
is not forced to collapse totally and close the air channel 
but both the film flow and air channel is strongly disturbed 
in the fitting. Nevertheless, this configuration allows to 
reach a significantly higher capacity as compared to the 
former case. Figure 7(c) displays the flow characteristics of 
the new Sovent high-flow fitting. Here, the cylindrical film 
flow passes through the fitting without experiencing any 
appreciable disturbance. Therefore, the air channel along 
the centreline of the fitting does not show any collapse or 
closing, either. A continuous air channel extending from 
the inlet up to the outlet of the stack including the fitting 
is clearly visible in this figure. 
Fig. 7: Flow characteristics of a Sovent high-flow system in comparison to a 
conventional single stack and a conventional Sovent stack.
3.3 Seal loss in a drainage system with high-flow 
Sovent fittings 
As discussed earlier in this paper, the flow conditions 
causing the emptying of the traps mounted on the 
drainage systems define the maximum capacity limits. 
These conditions are determined best and most directly 
23
2018 SYMPOSIUM CIB W062
 PONTA DELGADA-AZORES . PORTUGAL
DRAINAGE AND SANITATION (I)
by measuring the seal loss characteristics of the drainage 
systems. The seal water loss is a parameter to determine 
the severity of the dynamic pressure pulsations in the 
drainage piping systems. This method is used widely in the 
literature [6-8] for such purposes because of its simplicity 
to install and being a direct instrument indicating the level 
of trap water emptying. The seal water height measured 
given in such a study, can easily be converted into 
maximum suction or pumping pressure levels when it is 
required. 
In Figure 8, seal water loss for two different stack systems 
are given in comparison including a reference conventional 
single stack system and a stack composed of new Sovent 
high-flow fittings. Both stack systems are of dimension 
DN100. The reference system is tested with a maximum 
flowrate of 4.0 ℓ/s which is the allowable capacity for such 
a system with which a seal loss level of 50mm is supposed 
to be reached. The Sovent high-flow system is tested for 
two different flowrates of 4.0 and 12.0 ℓ/s. This way, it is 
possible to compare the results of the new system, on one 
hand directly with the reference case,on the other it is 
possible to display the significantly higher capacity of the 
newly designed fitting concept as compared to any other 
system of the same size.
 
Fig. 8: Seal loss characteristics of a Sovent high-flow system in comparison a 
conventional single stack at the maximum capacity loadings.
As observed in Figure 8, a maximum average seal loss of 
~65mm is recorded (Curve 1) in the reference case. This 
level is even higher than the commonly allowable 50mm 
for such stack systems and size. Curve 3 designates the 
seal loss values along the Sovent high-flow stack of this 
study at a flowrate of 4.0 ℓ/s. The average maximum 
seal loss reaches barely to a level of 5mm. This is almost 
a negligible seal loss level for building drainage systems. 
The Curve 2 depicts the seal loss distribution along 
the Sovent high-flow stack at a flowrate of 12.0 ℓ/s. As 
the flowrate is increased to this capacity, the seal loss 
increases to a maximum average level of ~32mm. Despite 
a significant increase in the capacity, only a moderate 
increase is observed in the seal loss level which is still well 
below 50mm allowable limit. It is noteworthy to mention 
here that there is theoretically still enough potential in 
the new Sovent system to increase the flowrate range 
further. However, Geberit specifies the upper limit of the 
new system as 12.0 ℓ/s for DN100 because the study of all 
technical risks of high-flow systems more than 12.0 ℓ/s in 
combination with other sanitary appliances contained in 
such systems remain open.
4 / Conclusions 
In this paper, it is reported on the main characteristics 
of a new high-flow Sovent concept which is capable of 
elevating the capacity of wastewater discharge systems in 
buildings significantly over the presently available systems. 
The hydrodynamic features of the concept are described 
in detail based on the results of some CFD simulations 
and extensive experimental investigations. The results 
obtained with the new fittings are always verified by 
comparisons with those of a well-known reference system 
as well as with those of some commonly installed systems 
in today’s buildings. 
It is shown in this paper that the new Sovent high-flow 
fitting increases the maximum attainable capacity of 
a discharge stack as much as 40% by combining the 
positive features of externally ventilated and conventional 
Sovent systems. The maximum capacity of a discharge 
stack fitted with Sovent high-flow fittings of dimension 
DN100 extends well over 12.0 ℓ/s. Moreover, this increase 
is achieved without upgrading the piping dimension 
24
of the high-flow fitting to a larger size than the present 
conventional fittings.
5 / References
Anonymous, European Standard EN 12056-2 Gravity 
drainage systems inside buildings- Part 2: Sanitary 
pipework, layout and calculation. European Committee for 
Standardization, June 2000.
Wylie RS and Eaton HN – Capacities of stacks in sanitary 
drainage systems for buildings, US Department of 
Commerce, National Bureau of Standards, Monograph 31, 
Washington D.C., July 1961
Cheng CL, Lu WH and Ho KC – Current design of high-rise 
building drainage system in Taiwan, 30th Int. Symp. on 
Water Supply and Drainage for Buildings, CIB W062, Sept. 
16-17, Paris, France, 2004.
Feurich H – Sanitärtechnik, Vol. 2, Chapter 12.4, Eight Ed., 
Krammer Verlag Düsseldorf AG, Düsseldorf, Germany, 
1999.
Jack LB, Swaffield JA and Filsell S – Identification of 
potential contamination routes and associated prediction 
of cross flows in building drainage and ventilation 
systems, 30th Int. Symp. on Water Supply and Drainage for 
Buildings, CIB W062, Sept 16-17, Paris, France, 2004.
Lu WH, Cheng CL and Shen MD – An empirical approach to 
peak air pressure on 2-pipes vertical drainage stack, 30th 
Int. Symp. on Water Supply and Drainage for Buildings, CIB 
W062, Sept 16-17, Paris, France, 2004.
Swaffield JA and Galowin LS – The Engineered Design of 
Building Drainage Systems, Ashgate Publishing Ltd, Hants, 
UK, 1992
Swaffield JA and Wise AFE – Water, Sanitary and Waste 
Services for Buildings, Fifth Ed., Butterworth-Heinemann 
Ltd, London, UK, 2002.
Flow-3D User Manual, Chapter 3 - Theory, Flow Science 
Inc., Santa Fe, USA, 2005.
Dr. Abdullah Öngören is the head of Basic 
Sanitary Technologies Department at Geberit 
International A.G. (Switzerland), where he is 
widely involved in research and development 
of sanitary equip-ment, and rain and waste 
water drainage systems. He is special-ized 
in flow induced vibration and noise and 
CFD applications in sanitary equipment and 
systems. He is currently conducting research in 
sanitary ceramic production processes.
Rolf Weiss is working at the Basic Sanitary 
Technologies Department at Geberit 
International A.G., where he is widely involved 
in research and development of sanitary 
equipment, and rain and waste water drainage 
systems. He is specialized in hydraulics and 
CFD applications in sanitary equipment and 
systems. His current research interest involves 
performance of building drainage systems.
6 / Presentation of Author(s) 
R. Weiss (1), A. Öngören (2)
(1) rolf.weiss2@geberit.com
 Basic Sanitary Technologies Dept., Geberit International AG, Switzerland
(2) abdullah.oengoeren@geberit.com
 Basic Sanitary Technologies Dept., Geberit International AG, Switzerland
25
2018 SYMPOSIUM CIB W062
 PONTA DELGADA-AZORES . PORTUGAL
DRAINAGE AND SANITATION (I)
Reducing the Bioaerosol impact inner bathroom by air and damp 
exclusion
M.C. LEE, H.T. TSENG, H. AOTA, A. IKEZAWA, Y. ARAKI, M. YAMAMOTO, C.L. CHENG, W.J. LIAO 
A3/
Abstract
Shower room and toilet are usually combined in one space 
as bathroom in Taiwan. Damp and odor always happen 
in the bathroom caused occupants uncomfortable even 
the health impacts. Lots of bioaerosol breed up by hot, 
humid and organically environment, such as fungal and 
bacteria to cause the mold problems and odor emission. 
This study investigates the domestic and public bathroom 
and samples the stain, odor and bioaerosol from the air 
and some wastes touched place, then analyzes the values 
of stain and odor, also cultivates the numbers of the 
bioaerosol. After investigation and analysis, increasing the 
air exchange by ventilation to exclude the air and damp is 
the way to remove the bioaerosol breeding conditions. In 
the other hand, changing the equipment and decorated 
materials with anti-stain and bacteria is the way to keep 
clean and less bioaerosol in the bathroom. 
Keywords
bioaerosol, bathroom, damp, odor, ventilation
1 / Introduction
Shower room and toilet are usually combined in one space 
as bathroom in Taiwan. Damp and odor always happen in 
the bathroom caused occupants uncomfortable even the 
health impacts. Lots of bioaerosol breed up by hot, humid 
and organically environment, such as fungal and bacteria 
to cause the mold problems and odor emission.
The growth of fungi requires oxygen, water, and nutrients 
[1], and the relative humidity range for growth is between 
75% and 95% [1]. The common place with the highest 
relative humidity at home is the bathroom. The damp 
while taking shower is filled in the air of the bathroom, 
the relative humidity can reach 95% or more, and that’s 
the sufficient moisture condition for fungi growth. The 
optimum temperature for most fungi growth is between 
15º and 30º [1]. In the bathroom, the temperature rises due 
to the hot water during the showing, and at the same time, 
the ventilation of the bathroom is not effective to exclude 
the damp. The moisture is often discharged in the ceiling 
and the corners of the bathroom. The human body organic 
substances such as washed hair and decorative substrates 
become a source of nutrients for fungi growth. Under such 
conditions, that is the most suitable environment for fungi 
growth. (Figure 1). When the fungi in the bathroom rapidlyproliferate, the increase of spores in the air even affects 
the air quality in other spaces, even more, excessive fungi 
growth can cause human health damage [3]. Many studies 
results have shown that the high intensity of fungus does 
cause health damage of occupants [1].
Fig. 1: Fungi in the corner of the bathroom.
Lee has ever collected the intensity of bacteria which from 
inner restroom is much higher than from outer restroom 
no matter in which building, as shown in Figure 2 [2]. That 
means the primary condition for bacterial growth in inner 
space of restroom is better than outer restroom.
Fig. 2: Bacteria intensity inner and outer the restroom in each building [2].
There are two kinds of odor emission sources in 
restroom: stool origin and urine origin. The former occurs 
instantaneously at the time of bowel movement, whereas 
the latter is generated continuously from the urine which 
is scattered and remains in restroom space. It is considered 
that urine-derived odor due to residual urine stain is often 
a problem in toilets with high temperature and humidity 
such as Taiwan in particular.
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Figure 3 shows a schematic diagram of the urine-derived 
ammonia odor generation mechanism [7] [8]. Urea in the 
urine is decomposed by the urease enzyme, which is a 
metabolite of the fungus, to be formed as ammonium ion 
as in the formula 1, and the pH rises due to the increase 
in the concentration of the ammonium ion. Dissolution of 
the ammonium ion is suppressed by pH rise, it becomes 
a free form and vaporizes and continues to develop as an 
odor. Due to this pH rise, phosphoric acid and calcium, 
magnesium and ammonium in the urine are precipitated 
as salts and become stuck stain called urinary stone. Since 
urinary stones are porous, fungi settle and propagate 
easily to promote ammonia production. 
Fig. 3: Mechanism of generation of urinary ammonia odor H2NCONH2 + 2H2O => 
2NH4+ + HCO3- Formula 1 [5].
After the 20th century, the shower room and toilet were 
usually combined in one space as bathroom. Damp and 
odor have become two major problems in bathroom 
space. We can reduce the health damage from fungus and 
bacteria.by effectively excluding damp, odor and organic 
substance. As shown in Figure 4. It is hoped that the source 
control, ventilation and ventilation methods, materials and 
construction can effectively reduce the harm caused by 
the bathroom space problem.
2 / Methodology
(1) Toilets subject to survey
In this research, we surveyed properties in Taipei City and 
Taichung City in Taiwan. In Taipei, we investigate the 
Fig. 4: Fungal and bacteria growth condition
total of 10 sites in 3 bathrooms and 3 public toilets and 
investigate 2 residential bathrooms and 2 public toilets.
(2) Survey method
a. Condition of field survey.
Measurement day of June was room temperature 29.6º - 
33.7º and relative humidity 56% RH - 75.4% RH, it was hot 
and humid, and there was a fungus odor easily occurred.
b. Collecting air fungal method
By collecting the fungi of the air in the bathroom to 
cultivate to verify the relationship between the damp in 
the bathroom and the intensity of fungi in the air. Figure 5 
shows collecting air fungal process.
Fig. 5: Collecting air fungal process.
c. Evaluation method of odor
The odor component in restroom space was measured 
for odor intensity and ammonia [8] [9] which is a major 
odor component. The odor intensity was smelled at the 
position where restroom user feels odor and smell at 
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2018 SYMPOSIUM CIB W062
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DRAINAGE AND SANITATION (I)
a distance of 15 cm from the odor generation location 
and organoleptically evaluated according to the six-step 
odor intensity indication method [10]. (Table. 1) The 
types of odors were also classified into 6 types. The odor 
components representing (i) - (v) are as follows. (Table. 2)
In order to specify the location of odor generation in 
detail, we investigated the amount of ammonium and the 
number of viable bacteria adhering to the surrounding 
instruments and building materials where the odor 
intensity is high.
Tab. 1: Level Odor Intensity.
Tab. 2: Type of smell.
3 / Investigation
(1) Air collection process
The culture dishes were placed in a machine and sealed 
with tape of different colors by different strains analyzed, 
as a sorting mark. At the beginning of the experiment, 
the instrument and the culture dish are placed outside 
the bathroom to avoid interference with the accuracy of 
the culture in the culture dish during preparation. After 
the culture dish is opened, the originally sealed tape is 
retained to seal the dish after collecting bacteria, as shown 
in Figure 6.
Fig. 6: Label and place the culture dish in the instrument.
Once the bathroom space is ready, place the instrument and 
culture dish in the measuring bathroom space (Figure 7). 
Fig. 7: Setup the air collecting instrument in the bathroom.
When the instrument is started to operate, the personnel 
must leave the internal space of the bathroom. The 
bathroom space is forbidden to walk or use for a minute 
while the instrument is starting. After one minute, the 
instrument will automatically make a sound, and then 
the culture dish will be taken out of the instrument, and 
the cover will be closed immediately to complete the 
sealing, so as to avoid other external factors affecting the 
cultured bacteria in the culture dish. Label the culture dish 
according to the time and location of the collection to 
analysis and use easily afterwards.
Fig. 8: Culture dish sorting and recording.
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The culture dish was taken out in a space of 25º for 48 
hours, and the bacteria were sorted according to the 
cultured species and dates. Counting the number of 
colonies on the instrument and take photos to analysis, as 
shown in Figure 8.
(2) Sampling of stain and bacteria
a. sampling of bacteria.
The number of samples and points are different by the 
selected toilets, as shown in Figure 9. Wipe the cotton 
swabs on the surface in the range of 2x2cm, as shown 
in Figure 10. The culture medium is incubated at a low 
temperature of 5º for 12 hours.
Fig. 9: Sampling points.
Fig. 10: Bacteria collecting process.
The bacterial cotton swab liquid placed at a low 
temperature of 5º was taken out and dropped into the 
bacterial test paper, and then the test paper was placed in 
a 35º oven for 24 hours to be taken out and observed, as 
shown in Figure 11.
Fig. 11: Bacterial test paper cultured.
The bacterial test papers that were placed in a 35oC oven 
for 24 hours were taken out, and the toilets and points 
were sorted by different marks, and the different presents 
of the bacteria on the test paper were compared with the 
look-up table to obtain the number of bacteria as shown 
in Figure 12.
Fig. 12: Bacterial test paper comparison.
b. sampling of stain
Quantity of adhered ammonium was measured by ion 
chromatograph by picking quartz wool impregnated with 
MilliQ water (Figure 13) with tweezers, wiping off a certain 
area (Figure 14), recovering it in a poly bottle, extracting 
with 5 mL of MilliQ water (Figure 15).
Fig. 13: MilliQ water.
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2018 SYMPOSIUM CIB W062
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DRAINAGE AND SANITATION (I)
Fig. 14: Toilet dirt collecting process.
Fig. 15: Adding pure water and chilling culture to the experiment.
Take the water chilled at a temperature below 5oC from 
the bottle by the needle tube, and squeeze the water with 
filtration into the new glass jar, and re-label the paper 
to complete the whole process of the scale collection 
experiment, as shown in Figure 18. Finally, the sampled 
water is analyzed by computer equipment to know the 
results of dirt concentration and composition.
4 / Result and Discussion
(1) Results of sensory evaluation
Figure 16 shows sampling points for sensory evaluation 
and Table 3 shows results of sensoryevaluation in public 
and residential restroom. In public restroom P1, the odor 
intensity on entrance and center of restroom was 4, and 
smell type was mainly (v) ammonia and trimethylamine. 
The odor intensity around urinals and squat toilet was also 
4, and smell type was mainly (v). In case of P2, the odor 
intensity of entrance and center of restroom was 2, around 
urinals and squat toilet was 3. The smell type of both of 
these points was mainly (v) ammonia and trimethylamine.
Additionally, in case of residential restroom, the intensity 
of odor was low value 2 on entrance, center of room and 
water closet.
As a result of sensory evaluation, we found that the odor 
intensity in the vicinity of urinals and squat toilet was 
tend to be high value (3-4), and the odor of ammonia and 
trimethylamine was main odor in public restroom. It was 
suggested that the main sources of odor in public toilet 
was urinal and squat toilet.
Fig. 16: Points for sensory evaluation.
Tab. 3: Results of sensory evaluation of public and residential restrooms.
Tab. 4: Detailed results of sensory evaluation of restrooms.
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Table.4 shown the detailed result of sensory evaluation 
in public and residential restroom. Because the odor 
intensity around a trap and floor was high value, we 
considered that the main source of odor existed around a 
trap and floor. As previously reported, the wet cleaning of 
restroom floor using a large amount of water accelerates 
rotting the compounds in urine on the tile gap, because of 
continuous wet condition. Consequently, we thought that 
the odor was generated by urine infiltrating in tile gap [6].
Fig. 17: Urinals and squat toilet in public restroom.
In addition, as sodium ion and the amount of aerobic 
bacteria were high value especially in the gap of squat 
toilet and floor, we considered that growth of bacteria 
is accelerated by moisture and compounds included in 
urine. The amount of aerobic bacteria was also high on the 
floor under urinal and the gap between squat toilet and 
floor. The results of quantitative analysis for P2 samples 
also have the same tendency.
Based on the above results, we concluded that the 
bacterial growth and decomposition of urine mainly 
causes generation of ammonia odor, consequently, the 
floor under urinals and the gap between squat toilet and 
floor was the main source of odor in public restroom.
(2) Results of quantitative analysis of fungal
After the collected air was cultured, it was found that 
the number of colonies formed on the culture dish had 
accounted for more than 95% of the whole culture dish, 
so that the number of colonies could not be counted, as 
shown in Figure 18. It can be seen that the amount of fungi 
in the air in the bathroom is very considerable.
Fig. 18: Fungi generated after air in the bathroom cultured.
(3) Results of quantitative analysis of stain and bacteria 
Table.5 shown the results of quantitative analysis for the 
ammonium ion and bacteria in public restroom P1 and 
P2. The amount of ammonium ion was high value on floor 
under urinal and the gap between squat toilet and floor 
(Figure 22.). Additionally, sodium ion was detected around 
floor under urinal and squat toilet. It is generally known 
that ammonium ion and sodium ion are contained in fresh 
urine as the value of 0.55 mg/L and 6.45 mg/L respectively 
[12], and the ratio of ammonium ion and sodium ion is 
approximately 1:12. However, the ratio of ammonium 
ion and sodium ion was higher than 1:12 in case of this 
sampling on the floor of P1. This results suggests that 
ammonium ion was generated by decomposition of 
compounds in urine infiltrating into the flooring material 
and tile joint.
Tab. 5: Results of quantitative analysis (public restroom). Tab. 6: Results of quantitative analysis (residential restroom).
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The results of quantitative analysis of stain and bacteria 
in residential restroom B1 are shown in Table 6. In case of 
residential restroom, the amount of ammonium ion and 
sodium ion was approximately ten percent of the amount 
in public restroom. This result shows that the amount of 
urine droplet was small. The amount of ammonium ion 
on the front rim of water closet was the highest value in 
residential restrooms B1 (Figure 23). This result suggests 
that urine splashed to front rim of water closet by sitting 
urination and remained on the front rim due to the 
difficulty of cleaning. Also in case of the floor sample, 
although we detected the ammonium ion as value of 
ten percent of public restroom samples, the amount of 
bacteria was equivalent to the results of public restroom. 
Generally, shower room and toilet are usually combined 
in one space as bathroom in Taiwan. Because of the floor 
of bathroom is always wet condition by using shower and 
poor ventilation, it is considered that the large amount 
of bacteria was detected from the floor of residential 
bathroom. This result is considered as the characteristic 
tendency of residential restroom in hot and high humidity 
condition, for example restroom in Taiwan.
Fig. 19: Water closet in residential restroom.
After analyzing the current situation, as shown in Figure 
20, the ammonia intensity of U4 sampling point in Figure 
9 of the urinal points is higher than that of U1, U2 and U3, 
which is the most polluted place. 
Also, as shown in Figure 21, the WC5 and WC6 sampling 
points in Figure 9 of the water closet points is higher than 
that of the WC1, WC2, WC3 and WC4.
As shown in Figure 22, the ST2 and ST3 sampling points in 
Figure 9 of the squat toilet points is higher than that of the 
ST1, which are the most polluted places.
5 / Renovated Design
Investigating the current situation, the polluted severity 
of the toilet is related to living habits and materials. The 
research proposes improvement strategies for the most 
serious contamination of the WC5 and WC6 (Table7, 1a-
1d). Improvements are proposed for the ST2 and ST3 
points where the squat toilet most polluted (Table 7, 2a-
2c), and the U4 points of urinary (Table 7, 3a-3b).
The growth of bacteria and fungi requires the 
indispensable factor, damp. How to effectively remove the 
Tab. 20: Ammonia intensity in each point of the urinal.
Tab. 21: Ammonia intensity in each point of WC.
Tab. 22: Ammonia intensity in each point of ST.
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damp generated during bathing from the bathroom space 
is the primary problem to solve. The study suggests the 
improvement of bathroom interior materials, ventilation 
methods and living behaviors, as shown in Table 8, to 
reduce the damage caused by damp in the bathroom. 
Material improvement methods show as 1a-1c. Ventilation 
improvement methods show as 2a, 2b. Living behaviors 
improvement methods show as 3a, 3b.
Tab. 7: Improvement strategies for toilets.
The current form of exhaust is mainly single-point exhaust. 
The single-point exhaust effect is insufficient due to the 
exhaust area is too small. To solve this problem, the linear 
exhaust method is suggested as option 1. The linear 
exhaust height is set of 150 cm for the showering behavior 
mainly below the shoulder of the Taiwanese average 
height is 160 cm. At present, the common exhaust speed 
is 0.1-0.3 m/s, so the minimum value of 0.1m/s is set as the 
simulated exhaust condition. The air inlets nowadays are 
mainly natural pressure air inlets. The air inlets are located 
at the door bottom about 30 cm away from the ground. 
The inlets are set for simulation, as shown in Table 10.
After the computer CFD simulation, it is found that the 
inlets cause the wind direction flow to form a ventilation 
short circuit problem, and the upper layer of damp is 
retained in the ceiling, shown as in Table10. Option 1 is not 
recommended.
Tab. 8: Improvement of excluding damp.
Tab. 10: Option 1 Improvement