The Ontario Building Code | Minimum Slope
7.4.8.1. Minimum Slope
(1) Except as provided in Sentences (2) and (3), every drainage pipe that has a size of 3 in. or less shall have a downward slope in the direction of flow of at least 1 in 50.
(2) Sentence (1) does not apply to a force main.
(3) Where it is not possible to comply with Sentence (1), a lesser slope may be used if it will produce a gravity flow of not less than 0.6 m per second.
In Plain Language
Except as otherwise provided, drainage pipe of 3 in. size or less must slope downward in the direction of flow at a minimum specified rate, ensuring waste and water actually flow rather than pooling in the pipe.
This is a plain-language summary of the 2012/2017 Ontario Building Code text above, for general understanding only and not a substitute for the Code. Always confirm current requirements against the 2024 edition (O.Reg. 163/24) or a qualified professional before construction.