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IAPMO Uniform Codes Spotlight

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From the 2015 UPC Illustrated Training Manual

608.7 Vacuum Relief Valves.
Where a hot-water storage tank or an indirect water heater is located at an elevation above the fixture outlets in the hot-water system, a vacuum relief valve that is in accordance with CSA Z21.22 shall be installed on the storage tank or heater.

If the water heater is installed above fixtures, there is a possibility of siphonage from the water heater. If the water supply is turned off or pressure drops as fixtures are being used, there is a possibility of a siphon being created because of the fixture water supply opening being lower than the tank. This could result in the tank emptying and possible steam being created in the tank. There have been instances where this siphonic action has been so powerful as to collapse the tank. For these reasons, a vacuum relief valve must be installed (see Figure 608.7).

The 2015 Uniform Plumbing Code Illustrated Training Manual eBook is available for purchase here.

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