Open vent boilers
An open vent boiler is the existing system in most people’s homes. This type of system uses two water tanks, both located in the loft, and a hot water storage cylinder in the airing cupboard so it is very space hungry. One tank draws water from the mains supply and feeds the storage cylinder which, when heated by the boiler, can release hot water to taps all over the house.
The second tank is the feed and expansion tank which contains the correct level of water for your heating system, allowing for water expansion when you turn the heat on.
Showers, taps and running baths can be drawn in any room at the same time, but be aware that if the cylinder should run cold it will take a little time to reheat.
Is this the right boiler for me?
Like system boilers, open vent systems allow you to run hot water from a range of outlets simultaneously, without the water running cold elsewhere in your house. The water pressure is low though, and you’ll only have drinkable water from one outlet, because it uses a storage system.
Unvented hot water cylinders
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 water 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.
They are ideal where high performance is required
Balanced pressures is available at hot and cold taps.
High pressure and hence flow rate of hot water eliminating the need for shower pumps etc
Fast filling baths.
If you currently have a cold-water tank in the loft but want to covert your loft space into an additional room, installing an unvented cylinder will eliminate the need for the tank, free up more space and you will have drinking water at all taps.