The Ontario Building Code | Premise Isolation
18.104.22.168. 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 22.214.171.124.(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)".