The Ontario Building Code | Non-Potable Connection
126.96.36.199. Non-Potable Connection
(b) an air gap.
(3) Where a clothes washer is supplied by a rainwatersystem and a potable water system, the potable water system shall be protected by dual check valve backflow preventers conforming to CSA B64.6, "Dual Check Valve (DuC) backflow Preventers" for,
(b) premise isolation.