Vented hot water storage system
Approved Document G, Sanitation, hot water safety and water efficiency, 2015 edition with 2016 amendments, defines a vented hot water storage system (or open hot water storage system) as: ‘a vessel fed with cold water from a dedicated storage cistern. Expansion of the water when it is heated is accommodated through the cold feed pipe. A vent pipe connecting the top of the vessel to a point open to the atmosphere above the cold water storage cistern is provided as a safety device.’
See also: Unvented hot water storage system (or closed hot water storage system)
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