(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)”.