Water Heaters Electric
Storage of 50L and Above
Free delivery over £50 

See Also  Small Under Sink Storage Units  Unvented 'mains pressure' units below 50L capacity are electrically heated and operate at the same mains pressure as the incoming cold water supply (typically 3 bar or so) and therefore provide excellent hot water flow rates.  

Sales and Technical 01751 411965
Simple guide to electric water storage heaters over 50 litres capacity. Unvented hot water cylinders are now the most popular option for new hot water systems and operate at the same mains pressure as the incoming cold water supply (typically 3 bar or so) and therefore provide excellent water flow rates without requiring an header tank in the loft space or additional pumps. The more traditional 'vented' hot water cylinder operates with a header tank and generates lower water pressure than an unvented cylinder.  In 'Direct' units the water is heated by one or more electric immersion heaters. In 'Indirect' units the heat source is an external boiler that circulates hot water through a coil heat exchanger within the cylinder. Indirect cylinders are generally more expensive to purchase and install but usually result in faster reheat times.  Direct (all-electric) units come into their own when a gas/oil boiler is either not available or too expensive to install, or in situations where the requirement for annual gas safety checks of appliances, flues and pipework is considered onerous, for example at rental properties. Combination units have an integral cold header tank and do not need any special valves. All that is required is to connect to the water supply and to power. They are thus ideal when speed and simplicity of installation is the key but they provide poor pressure for showers and have to be wall mounted as high as possible.

  Unvented direct cylinders operate at mains pressure and are heated by electric immersion heaters. Hot water pressure is very good.    Unvented indirect cylinders operate at mains pressure and are heated by an separate (external) boiler. Hot water pressure is very good. 

Vented direct cylinders are supplied by a low pressure header tank and are heated electrically. Hot water pressure is relatively low.  

Vented direct cylinders are supplied by a low pressure header tank and are heated by an external boiler. Hot water pressure is relatively low.

   Combination units feature an integral cold water cistern and hot water storage. Installation is normally straightforward but hot water pressure can be low.

Unvented Direct
Mains Pressure Electric

Unvented Indirect
Mains Pressure Boiler

Vented Direct
Low Pressure Electric

Vented Indirect
Low Pressure Boiler

Combination
Low Pressure Electric