### Building (Standards of Sanitary Fitments, Plumbing, Drainage Works and Latrines) Regulations 《建築物(衞生設備標準、水管裝置、排水工程及廁所)規例》

17. Flushing water supply
(1) A system of plumbing shall be provided for the supply of water for flushing purposes to every watercloset fitment, trough watercloset, urinal and slop sink.
(2) Every part of any such system of plumbing (including any storage tank for water solely for flushing purposes) shall be constructed of material that is suitable for use with salt water. (L.N. 113 of 1964)

18. Flushing rim
Every watercloset fitment, bidet, basin-type urinal and slop sink shall be provided with a suitable flushing rim for the effectual flushing of the fitting.

19. Flushing cisterns
(1) Save as provided in regulation 20, every watercloset fitment, trough watercloset, urinal and slop sink shall be provided with a flushing cistern.
(2) Such flushing cistern shall—
(a) in the case of watercloset fitments and slop sinks—
(i) discharge to the watercloset fitment of slop sink, on each occasion such fitment is used, not less than 9 L and not more than 14 L of water; and
(ii) be provided with a ball valve so arranged as to re-fill the cistern within 2 minutes;
(b) in the case of trough waterclosets, be fitted with automatic discharging apparatus so arranged as to discharge—
(i) at the highest point of the channel;
(ii) at such intervals as may be necessary of ensure adequate cleaning of the closet, 
not less than 9 L of water for every metre of the channel;
(c) in the case of urinals, be fitted with automatic discharging apparatus so arranged as to discharge—
(i) into every basin or stall or, in the case of a trough urinal, every metre thereof;
(ii) at such intervals as may be necessary to ensure adequate cleaning of the urinal,
not less than 4.5 L of water. (L.N. 294 of 1976; E.R. 3 of 2020)

20. Pressure valves
Save in the case of trough waterclosets and urinals, pressure valves may, where there is a suitable head of water, be installed for flushing purposes without the provision of a flushing cistern.

### Building (Standards of Sanitary Fitments, Plumbing, Drainage Works and Latrines) Regulations 《建築物(衞生設備標準、水管裝置、排水工程及廁所)規例》

21. Flushing pipes
The internal diameter of flushing pipes shall—
(a) in the case of watercloset fitments, trough waterclosets and slop sinks, be not less than 32 mm;
(b) in the case of urinals (other than trough urinals), be not less than 15 mm for each basin or stall; and
(c) in the case of trough urinals, be not less than 15 mm for every metre thereof.
(L.N. 294 of 1976)

22. Storage tanks for flushing water
(1) Storage tanks for water solely for flushing purposes shall be provided in every building in which watercloset fitments, trough waterclosets, urinals or slop sinks are installed.
(2) Every such tank shall—
(a) at a position above the level of the highest fitment or on a suitable water tower;
(b) fitted with a suitable close fitting cover; and
(c) provided with adequate access to enable the tank to be entered and cleaned.

23. Overflow pipes
(1) Every flushing cistern and water storage tank shall be provided with an overflow pipe.
(2) The overflow pipe from a water storage tank shall—
(a) have an internal diameter of one commercial size larger than the supply pipe to the cistern or tank; (L.N. 361 of 1980)
(b) dip down, inside the tank, so as to terminate in a position not more than 150 mm above the bottom of the tank; and (L.N. 294 of 1976)
(c) discharge in a conspicuous position.

24. Traps for soil fitments
(1) Every soil fitment shall be provided with a suitable trap with a water seal of not less than 50 mm.
(2) The internal diameter of every such trap shall be not less than—
(a) 80 mm, in the case of a watercloset fitment, slop sink, or urinal with more than 3 basins or stalls or with a channel longer than 2 m;
(b) 50 mm, in the case of a urinal with more than one and not more than 3 basins or stalls or with a channel not longer than 2 m;
(c) 40 mm, in the case of a bidet or urinal with a single basin or stall; and
(d) 100 mm, in the case of a trough watercloset.
(L.N. 294 of 1976)

### Building (Standards of Sanitary Fitments, Plumbing, Drainage Works and Latrines) Regulations 《建築物(衞生設備標準、水管裝置、排水工程及廁所)規例》

25. Traps for waste fitments
(1) Every waste fitment shall be provided immediately under the fitment with a suitable trap:
Provided that a trap shall not be required—
(a) where the waste pipe from such fitment—
(i) does not exceed 1 m in length; and
(ii) discharges over or into a suitable trapped gully;
(b) in respect of lavatory basins, where the waste pipes therefrom discharge in the manner provided by regulation 12(2);
(c) in respect of a range of shower baths, where the drainage channel provided therefor is provided, at its lowest point, with a trap.

(2) Save as provided in paragraph (3), every trap provided for a waste fitment shall have—
(a) an internal diameter of not less than 32 mm; and
(b) a water seal of not less than 40 mm.
(3) Where the waste pipe from a waste fitment is, under the provisions of regulation 12(3), connected to a soil pipe, the trap provided for the waste fitment shall—
(a) have an internal diameter of not less than 32 mm;
(b) have a water seal of not less than 80 mm; and
(c) be—
(i) adequately ventilated; or
(ii) constructed to prevent loss of water seal.
(L.N. 294 of 1976)

26. Soil pipes
(1) The internal diameter of every soil pipe from a watercloset fitment or slop sink shall be not less than—
(a) 80 mm; or (L.N. 294 of 1976)
(b) the internal diameter of the outlet pipe of the trap of any fitment to which the soil pipe is connected,
whichever is the greater.
(2) The internal diameter of every soil pipe from a urinal or bidet shall be not less than the internal diameter of the outlet pipe of the trap of any fitment to which the soil pipe is connected.
(3) Every soil pipe shall be properly connected to a covered drain without the intervention of any trap.