Unvented pressurised hot water cylinders sometimes called ‘Megaflo’ cylinders store water supplied directly from the mains water supply and essentially act as a hot water storage cylinder, whereas vented cylinders are directly connected to the cold water storage tank that is usually held within the loft in most homes.
Unvented cylinders heat water using electrical heating elements or heat directly from the boiler or can be configured to work with solar thermal.
The pressurised hot water cylinders store water at relatively high pressures; they are therefore able to supply water at similar pressures to the cold water supply. The increased pressures also make for better quality showers, without the need for pumps. With both hot and cold water services fed from the mains, there is no more need for a cold water storage tank, keeping loft spaces clear, and pipe work to a minimum.
This type of mains pressure cylinder is becoming more and more popular in the UK, with more homeowners requiring mains pressure hot water as standard.
Be sure to check that anyone who installs or works on your unvented hot water cylinder holds the correct qualifications. It is not just the Law, but due to the nature of unvented hot water cylinders, and the properties of pressurised systems, it is a matter of safety. Note: Worcester Bosch are currently offering a 10 year guarantee on a boiler, filter and cylinder installation.