The Ontario Building Code | Thermal Expansion
7.6.1.16. Thermal Expansion
(1) Protection against thermal expansion shall be required when a check valve is required by Article 7.6.1.10., a backflow preventer is required by Article 7.6.2.2., or a pressure reducing valve is required by Article 7.6.3.3.
7.6.2. Protection from Contamination
In Plain Language
Thermal expansion in a closed water heating system must be accommodated per this article, since heated water expands and can otherwise build dangerous pressure in a sealed system.
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.