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This category covers equipment that heats and stores hot water: unvented cylinders, point-of-use and multipoint electric water heaters, instantaneous handwash heaters and boiling water units. The right choice depends on how much hot water is needed, where, and how it will be heated.

Cylinders

An unvented cylinder is fed straight from the cold water main, with no open vent pipe, and supplies hot water at mains pressure. An indirect cylinder is heated by a coil connected to a boiler or other heat source, usually with an immersion heater as back-up, while a direct cylinder is heated inside the vessel itself, typically by immersion heaters. Check the capacity in litres and the dimensions, leaving room to reach the valves for servicing.

Water heaters

Point-of-use storage heaters hold a few litres close to a sink or basin, multipoint heaters hold more and can serve several outlets, and instantaneous heaters warm water as it flows instead of storing it. Boiling water units provide near-boiling water for drinks. Check the capacity, the power rating in kW and the electrical supply each unit needs.

Safety and regulations

Unvented systems need at least two independent safety devices, such as an energy cut-out and a temperature relief valve. In England, unvented hot water storage over 15 litres must be installed by a competent person under Building Regulations Part G (G3), and the work is notifiable unless the installer belongs to a competent person scheme. A new electrical circuit for a water heater is notifiable under Part P and must be done by a registered competent person or notified to building control. Fittings on drinking water must be suitable under the Water Supply (Water Fittings) Regulations 1999.

See the ranges of unvented cylinders and electric water heaters.