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BEAM PLUS FOR NEW B UILDINGS WATER USE (WU)
V ERSION 1.2 WU 6 EFFLUENT DISCHARGE TO FOUL SEWERS
Copyright © 2012 BEAM Society Limited. All rights reserved.
Page 134
5 WATER USE 5.2 EFFLUENT
WU 6 EFFLUENT DISCHARGE TO FOUL SEWERS
EXCLUSIONS None.
OBJECTIVE Reduce the volumes of sewage discharged from buildings thereby
reducing burdens on municipal sewage supply and treatment facilities.
CREDITS ATTAINABLE 1
PREREQUISITES Compliance with the Water Pollution Control Ordinance, and the Building
(Standards of sanitary fitments, plumbing, drainage works and latrines)
Regulations Chapter 123 Regulation 17.
CREDIT REQUIREMENT 1 credit for demonstrating a reduction in annual sewage volumes by 20%
or more.
ASSESSMENT Where the Client can demonstrate that the target percentage of
reduction in annual sewage volume can be achieved, either based on the
default assumptions for the calculation procedure given in Appendix 8.6
or any other appropriate estimation, the credit(s) shall be awarded.
BACKGROUND Demand for flushing and potable water should be assessed with regard
to Building (Standards of Sanitary Fitments, Plumbing, Drainage Works
and Latrines) Regulation 10A(4). "Potable water" refers to a supply of
water for the purposes of Regulation 10A(2) [1]. The quantity of flushing
water required is given in PNAP 17 [2].
Regulation 19 of the Building (Standards of Sanitary Fitments, Plumbing,
Drainage Works and Latrines) Regulations (Drainage Regulations)
requires flushing cisterns of water closet fitments to have a discharge
between 9 and 14 litres. Under the current Waterworks Regulations,
flushing cisterns shall be of the valveless syphonic type and the flushing
volume shall be within the range of 7.5 and 15 litres [3].
With the application of modern technology in the design of water closet
flushing systems, the effectiveness of flushing can be maintained with a
reduced discharge. Therefore, to conserve our valuable water resources,
both the Building Authority (BA) and Water Authority would have no
objection to relaxing the use of syphonic flushing cisterns with discharge
less than that required by the current regulations provided that the
associated toilet bowls are compatible with the cisterns and the syphonic
action is sufficient for the wastes in the toilet bowls to be cleared
effectively by a single flush. WSD has relaxed the requirements in
respect of the flushing mechanism and minimum flushing volume as
follows:
 the use of valve type flushing devices (mechanical or sensor type
with single flush or dual flush) in addition to valveless syphonic type
flushing apparatuses; and
 the use of flushing devices which are able to give a single flushing
1 Department of Justice, CAP 123I building (Standards of Sanitary Fitments, Plumbing, Drainage Works and Latrines)
Regulations
DBE/$FILE/CAP_123I_e_b5.pdf
2 Buildings Department. Practice Note for Authorized Persons, Registered Structural Engineers and Registered
Geotechnical Engineers. PNAP No. APP-4 Water Supply and Wells.
3 Buildings Department. Practice Note for Authorized Persons, Registered Structural Engineers and Registered
Geotechnical Engineers. PNAP No. APP-99Flushing Volume for Flushing Cisterns.