7.4.6.4.

(1) Except as permitted in Sentence (2), a backwater valve that would prevent free circulation of air shall not be installed in a building drain or in a building sewer.

(2) A backwater valve may be installed in a building drain provided that,

(a) it is a “normally open” design conforming to,

(i) CAN/CSA-B70, “Cast Iron Soil Pipe, Fittings, and Means of Joining”,

(ii) CAN/CSA-B181.1, “ABS Drain, Waste, and Vent Pipe and Pipe Fittings”,

(iii) CAN/CSA-B 181.2, “PVC Drain, Waste, and Vent Pipe and Pipe Fittings”, or

(iv) CAN/CSA-B182.1, “Plastic Drain and Sewer Pipe and Pipe Fittings”, and

(b) it does not serve more than one dwelling unit.

(3) Except as provided in Sentences (4) and (5), where a building drain or a branch may be subject to backflow, a backwater valve shall be installed on every fixture drain connected to them when the fixture is located below the level of the adjoining street.

(4) Where more than one fixture is located on a storey and all are connected to the same branch, the backwater valve may be installed on the branch.

(5) A subsoil drainage pipe that drains into a sanitary drainage system that is subject to surcharge shall be connected in such a manner that sewage cannot back up into the subsoil drainage pipe.