Unvented Cylinder Installation
An unvented hot water cylinder is a water vessel which holds heated water under extreme pressure, feeding it out when a hot water tap or appliance is opened and providing instant hot water. Because the system is completely pressurised, there is no need to vent it to the atmosphere – hence the name.
Unvented hot water cylinders have been fitted in the UK since 1986 and have seen massive growth in popularity over the years. Unlike vented systems, unvented hot water cylinders do not require a cold water tank and so save domestic users space within their homes. The sealed cylinder is instead fed directly from the cold mains, and since the mains water enters under high pressure, the flow rates and consistency from an unvented cylinder tend to be more reliable.
Unvented hot water cylinders are typically made from stainless steel, which is a relatively thin and high tensile material capable of expanding with the hot water and withstanding the extreme pressures and high temperatures. Heavy gauge copper is sometimes used as an alternative, but while these might be better for storing hot water, they are also much more expensive.