Unvented hot water storage system
Approved Document G, Sanitation, hot water safety and water efficiency, 2015 edition with 2016 amendments, defines an unvented hot water storage system (or closed hot water storage system) as: ‘…a vessel fed with cold water from a supply pipe or dedicated storage cistern (without a vent pipe) and in which water is heated directly or indirectly. Expansion of the water when it is heated is accommodated either internally or externally and the system is fitted with safety devices to prevent water temperatures exceeding 100C, and other applicable operating devices to control primary flow, prevent backflow, control working pressure and accommodate expansion.’
See also: Vented hot water storage system.
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