Unvented Hot Water

Why unvented hot Water?

Our engineers are fully qualified in installing and maintaining High Pressure Unvented Hot Water Systems.


Unvented Hot Water Systems are more commonly used in Europe and the US. Although  a British invention, they only become legal to install in the UK since 1989.


When an un-vented hot water system is installed both the hot and the cold water supplies within the dwelling, deliver water at the taps or shower outlet at mains pressure. Cold water from the mains is delivered to the base of the cylinder, the water is heated, then when a tap or shower is turned on the mains water pressure pushes the hot water out. 


To allow the water that is heated in the cylinder to expand as it is heated, an internal or external expansion vessel is used; a pressure relief valve is also fitted should the vessel fail.

An un-vented hot water storage cylinder can be heated directly via an immersion heater or indirectly incorporating the central heating system.