Types of Water Heating Systems
DIFFERENT TYPES OF WATER HEATERS
If your hot water system is vented, you may have:
An electric immersion heater, which heats the water inside a hot water cylinder. Sometimes two are fitted.
A water heating boiler, which heats the water and transfers it to a hot water cylinder. There may be a back-up immersion heater.
Central heating, in which water heated by the boiler heats the water inside the hot water cylinder via a coiled heat exchanger. Again, there may be a back-up immersion heater.
If your hot water system is unvented, you may have:
A separate ‘instantaneous’or electric heater. Single-point heaters supply one hot tap while multi-point heaters supply several taps. Larger versions also have a built-in hot water storage tank.
A combination system (eg ‘Combi’) in which a central heating boiler and ‘instantaneous’ heater are combined with a small storage tank.
UNVENTED HOT WATER SYSTEM
Water is fed to the heater — and from here to the hot taps — at mains pressure. Expansion occurs within the heater (or in a sealed expansion vessel) and there are a number of safety devices built-in to release steam if the system overheats.
WHO IS RESPONSIBLE FOR THE WATER SUPPLY?
The water undertaking is responsible for the supply up to and including their stopvalve. If the valve no longer works, you can ask them to fix it.
You are responsible for the rest of the system, including the service pipe and rising main. If either pipe gets damaged, the water undertaking can make you carry out repairs (though this should be covered by your house insurance).