Section 27(11) in Haryana Municipal Drainage and Sanitation Bye-laws, 1977
(11)Where the water closet discharges into a soil pipe which also receives the discharge from another water closet i.e. where there is another water closets pan above the other, the trap of the water closet shall be ventilated by a pipe called "antisyphonage pipe" which shall :-(a)have an internal diameter of not less than 50 mm. ;(b)be connected with the arm of the soil pipe at a point not less than 7.5 cm. and not more than 30 cm. from the highest part of the trap, on that side of the water seal which is nearer to the soil pipe and in the direction of the flow ; and(c)either have an open and as high as the top of soil pipe or be carried into a soil pipe at a point not less than 1.5 metres above the highest connection of the soil pipe.
