BEAM Plus Interiors Manual

99 / 210

BEAM PLUS INTERIORS
COMMERCIAL, R ETAIL AND INSTITUTIONAL
WATER USE (WU)
WU 3 EFFLUENT DISCHARGE TO FOUL S EWERS
Copyright © BEAM Society Limited. All rights reserved. Page 98
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)[ .
The quantity of flushing water required is given in PNAP 17 ].
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
].
With the application of modern technology in the design of water
closet flushing system, 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 lower discharge 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 waste 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:
i. the use of valve type flushing devices (mechanical or sensor
type with single flush or dual flush) in addition to valveless
syphonic type flushing apparatus;
ii. the use of flushing devices which are capable to give a single
flushing volume of less than 7.5 litres.
The capacity of the flushing cistern in the case of trough water-closets
and urinals shall be approved by the Water Authority subject to the
discharge in the case of trough water-closets being not less than 9
litres of water for every metre of the channel and the discharge in the
case of urinals being not less than 4.5 litres of water for every urinal
stall, or in the case of a trough urinal, every metre thereof.
1 Department of Justice, CAP 123I building (Standards of Sanitary Fitments, Plumbing, Drainage Works and Latrines)
Regulations
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.