Unvented hot water system explained

Unvented hot water system explained? An unvented hot water system is a sealed mains water-supplied cylinder that produces and stores domestic hot water and hence distributes it at mains pressure rather than gravity pressure from a loft tank as is used in an open-vented system.

It is pressured to improve shower flow, speed up bath filling and provide a more uniform performance when many outlets are being used simultaneously. It also saves space, as there is no requirement for a cold water storage tank in the loft.

Normally the system is heated by an external heat source, such as a boiler or heat pump in an indirect unvented cylinder configuration or sometimes by immersion heaters in a direct unvented cylinder configuration.

As water heats, it expands; thus, the system needs safety components like an internal air gap or external expansion vessel and a temperature and pressure relief valve to ensure it works safely.

It is crucial to note that unvented cylinders are a sealed, pressured system and therefore must be installed and serviced by a certified engineer. When correctly fitted and maintained, they are a very efficient and practical means of storing residential hot water.

In basic terms, an unvented system produces and stores hot water under pressure, provides powerful mains-pressure hot water and employs built-in safety controls to manage the pressure securely and safely.