The Ontario Building Code | Increaser or Reducer
7.3.3.5. Increaser or Reducer
(1) Every connection between two pipes of different size shall be made with an increaser or a reducer fitting installed so that it will permit the system to be completely drained.
In Plain Language
Where two pipes of different sizes connect, the transition must be made with a proper increaser or reducer fitting installed the right way, rather than an improvised connection.
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.