16. Water closets
(1) The pan shall be of non-absorbent material so constructed as to receive and contain sufficient water and to allow any filth to fall free of the sides directly into the water.
(2) The flushing apparatus shall be such as to secure the prompt and effectual flushing and cleansing of the pan. It shall be supplied with an adequate supply of water and shall not be automatic in operation.
(3) The pan shall be provided with a sufficient trap which shall not be a “D” trap or Masons Dipstone. Where the contents of the pan discharge into a soil pipe which also receives the discharge from another pan or waste fitting or other soil fitting the trap of the pan shall be ventilated by an anti-syphonage pipe having an internal diameter not less than 2 inches and be connected with the arm of the soil pipe at a point not less than 3 and not more than 12 inches from the highest part of the trap on that side of the water seal which is nearer to the soil pipe and shall have an open end as high as the top of the soil pipe or shall be carried into the soil pipe at a point not less than 3 feet above the highest connection to the soil pipe.
(4) The water closet—
(a) shall be entered either directly from the external air, or from a ventilated lobby or directly from a room used solely for sleeping;
(b) shall have at least one external wall, or a roof, and shall have a window of an area of 2 square feet exclusive of the frame and in addition a permanently open ventilation of at least 50 square inches;
(c) shall have openings for light and ventilation which shall be placed at as high a level as practicable on the external wall, or in the roof, and shall communicate directly with the external air.
(5) Where the pan is to be fixed—
(a) above floor level the whole of the pan and the trap thereto shall be fixed entirely above the level of the floor of the water closet and shall not be cased round or enclosed in any manner;
(b) below floor level it shall be supported on a sub-floor in such a manner that the upper face of the squatting slab shall be at the level of the floor of the water closet and the pan and the trap thereto shall be encased in concrete at least 3 inches thick.