7.6.2.5A.Backflow from Buildings with a Solar Domestic Hot Water System

(See Note A-7.6.2.5A.) (1) Except as permitted by Sentence (2) and as provided in Sentences (3) and (4), a potable water system shall be protected against backflow where the heat transfer loop of a solar domestic hot water system is directly connected to the potable water system. (2) Where the heat transfer loop of the solar domestic hot water system consists of direct flow-through of potable water only, protection against backflow is not required. (3) A potable water system that is directly connected to the heat transfer loop of a solar domestic hot water system that serves a residential occupancy within the scope of Part 9 shall be provided with a backflow preventer selected in accordance with CAN/CSA-F379.1, “Packaged solar domestic hot water systems (liquid-to-liquid heat transfer) for all- season use.” (4) Where a solar domestic hot water system includes a single wall heat exchanger and contains only a relatively harmless heat transfer fluid as described in CAN/CSA-F379.1, “Packaged solar domestic hot water systems (liquid-to- liquid heat transfer) for all-season use”, the backflow prevention required in Sentence (1) is permitted to be a dual check valve backflow preventer conforming to CSA B64.3, “Dual Check valve backflow preventers with atmospheric port (DCAP)”.