The Ontario Building Code | Premise Isolation
7.6.2.6. Premise Isolation
(1) buildings or facilities where a moderate hazard or severe hazard may be caused by backflow shall be provided with premise isolation of the potable water system by the installation of a backflow preventer selected in accordance with Clauses 5.3.4.2.(b) and (c) of CSA B64.10, "Selection and installation of Backflow Preventers".
(2) Buildings of residential occupancy within the scope of Part 9 are not required to be isolated unless they have access to an auxiliary water supply.
(3) Except as provided in Sentence (1), where no direct connection exists between the auxiliary water supply and the potable water system, premise isolation shall be provided by a dual check valve backflow preventer conforming to CAN/CSA-B64.6, "Dual Check Valve Backflow Preventers (DuC)".
In Plain Language
Premise isolation, protecting the public water supply from contamination originating inside a single building, is required per the conditions set out in this article.
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.