In Plain Language

A T fitting can't be used in a drainage system except to connect a vent pipe, and a cross fitting can't be used in a drainage system at all, since these fitting geometries can cause improper flow and blockages in waste lines.

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.