A vented hot water cylinder is a popular system you will find in many homes around the country. The vented cylinder works by storing cold water from the mains in a tank and, subsequently, it can be heated and fed to any of the appliances in your house that require it
Vented systems are known as ‘gravity fed hot water systems’.
Vented cylinders (also called open-vented cylinders) need to be supplied by a large tank of cold water which is kept in the loft. The natural pull of gravity carries this water via a vent pipe down to the hot water cylinder which heats the water.
Vented cylinders rely on gravity and the height of the cold water tank dictates the pressure. The greater the height, the more powerful the water pressure. This means that the cold water tank should be placed in the loft.
As the water is heated it expands, but the presence of the vent pipe and tank in the loft provides an escape route for the excess.