Information and advice for anyone who uses heating equipment at home
or work and is off the mains gas network
Unvented hot water tanks
Unvented hot water tanks have become increasingly popular in recent years. Unvented systems don't require a cold water storage tank, so there is no need to have a cold water tank in the loft, which is ideal if you are pushed for space and also offers more flexibility when siting the hot water tank.
Instead, the sealed hot water cylinder is fed directly by the cold water mains. Since this operates at mains pressure, it offers much better flow rates, meaning your shower and bath performance should be higher. Unvented hot water tanks need an expansion vessel to be fitted to allow space for the water in the system to expand as it heats up. They also come with other safety mechanisms, such as pressure relief valves and twin thermostats.
Because an unvented system is pressurised, it is important to have it installed and serviced regularly by a suitably qualified heating technician. To provide guidance on what to expect during a servicing visit, the Hot Water Association has produced a useful guidance leaflet which is available to download here.