Hong Kong Regulations

BUILDING (STANDARDS OF SANITARY FITMENTS, PLUMBING, DRAINAGE WORKS AND LATRINES) REGULATIONS - REGULATION 30

Anti-syphonage pipes

(1) Where-

   (a)  more than one trap of a watercloset fitment, urinal, slop sink or
        waste fitment is connected with one soil pipe; or

   (b)  more than one trap of a waste fitment is connected with one
        waste pipe, the traps shall be ventilated by means of
        anti-syphonage pipes: Provided that if, in the case of waste fitments,
        the traps to such fitments are constructed to prevent loss of water
        seal, it shall not be necessary to provide an anti-syphonage pipe,
        unless the Building Authority so requires.

(2) Every anti-syphonage pipe shall be connected with-

   (a)  the trap, if the connexion with the anti-syphonage pipe is an integral
        part of the trap; or

   (b)  the branch soil pipe or branch waste pipe-

        (i)    on the side of the water seal nearest the main soil pipe or
               waste pipe; and

        (ii)   at a point not more than 300 mm from the trap outlet. (L.N. 294
               of 1976)

(3) The internal diameter of every anti-syphonage pipe shall-

   (a)  if the diameter of the soil pipe or waste pipe to which it is
        connected is 80 mm or more, be not less than 50 mm;

   (b)  if the diameter of such soil pipe or waste pipe is less than 80 mm, be
        not less than-

        (i)    two-thirds of the internal diameter of such soil pipe or waste 
               pipe; or

        (ii)   32 mm, whichever is the greater. (L.N. 294 of 1976)

(4) (a) The main anti-syphonage pipe may be connected to a soil pipe which,
under regulation 31(3), is acting as a ventilating pipe;

   (b)  every such connexion shall be made at a point above the flood level of
        the highest fitment connected to the soil pipe.