If you are thinking of installing a power shower there is one thing that needs to be emphasised - it does not heat water - it merely pumps existing tank-fed hot water together with tank-fed cold water to produce a high pressure shower with excellent rates of flow.
A power shower cannot be used with combination boilers, invented heating systems or with mains pressure cold water.
A power shower is usually installed with a variable spray shower head that can produce different spray patterns including massage or pulse.
Power showers come in two distinct varieties, the integral power shower and the composite power shower
Integral Power Shower
Integral power showers consist of a small pump, together with a mixer valve housed in a compact that is fitted to the wall inside the shower enclosure or above the bath. They usually come complete with a slider rail kit and a variable spray pattern shower head. Although they look similar, you cannot use a power shower to directly replace an existing electric shower - they require totally different plumbing and electric supplies (electric showers require and mains pressure water - although there are some that will operate of low pressure cold water- and a separate electrical supply run back to the mains that must conform with electrical regulations)
Composite Power Shower
Composite power showers consist of a pump, a shower mixer valve and spray head. There are several different types of shower pump available so make sure you choose one that is suitable for your particular situation. The pump can be hidden away in an airing cupboard or under the bath if there is room - although you need to ensure that you can gain access to the pump in case maintenance is required. The shower pump is usually activated by flow switches which switch the unit on as soon as it detects water flowing (i.e. when the shower mixer is turned on) and switches the pump off when the water stops flowing.
Composite power showers tend to cost a little more than the integral type, but are much neater and give you the option of choosing a shower mixer that suits the overall look of the room, including recessed mixer valves.
Power showers can be prone to temperature fluctuations when water is used by others in the house whilst the unit is in operation. This can be avoided by installing a thermostatic power shower (or a thermostatic shower mixer if using a composite power shower). A thermostatic power shower will stabilise the temperature and prevent scalding.
A power shower, as its name suggests, produces a powerful jet of water. Most shower cubicles are designed to handle power showers but care must be taken if you are planning on using a power shower with a bath shower screen or shower curtain as splashed water might escape the showering area.
Another thing that must be taken into consideration is that power showers can use a lot of water if used for prolonged periods. A power shower run on its highest setting for 10 minutes could fill a bath. If people will be using the shower one after the other, you might find you will run out of hot water!