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Fitting an electric shower

Cost: Difficulty:


Electricity is dangerous and can be hazardous. In doubt? Call a qualified electrician.

Selecting cable size

To select the correct cable size see the Selecting cable size page. It is very important that the correct size cable is used.

Site requirements


The installation must be in accordance with local Water Authority bylaws. To ensure correct operation of the shower it must be connected to a mains water supply with a minimum running pressure of 1.0 bar (14.5 lbs per square inch) at a flow rate of 8 litres/minute and a maximum static running pressure of 10 bar (145 lbs per square inch).

Instantaneous showers can have the water supply taken from a cold water storage cistern provided there is a minimum head of 10 metres (i.e. the vertical distance from the base of the cistern to the sprayhead). It must be an independent supply to the shower only. If it is intended to operate the shower in hard water areas or a pressure above or below the minimum or maximum stated, contact a Service Engineer.


A separate permanently connected supply must be taken from the consumer unit to the shower via a double pole linked switch with a minimum contact gap of 3mm in both poles. The switch can be a ceiling mounted pull cord type or a wall mounted switch. The switch must be readily accessible and clearly identifiable, but out of reach of a person using a fixed bath or shower, except for the cord of a cord operated switch. The wiring must be connected to that switch without the use of a plug or socket outlet.

NOTE: Where shower cubicles are located in rooms other than bathrooms, any socket outlet in that room must be situated at least 2.5 metres from the shower cubicle. The supply cable and circuit protection must conform to IEE wiring regulations and be sufficient for the amperage.

If in doubt contact a qualified Electrician or Service Engineer.


Siting of the shower

NOTE: The shower must not be positioned where it will be subjected to freezing conditions. For ease of servicing the unit must always be mounted on the surface of tiled walls, never tile up to the unit.


Position the unit vertically, where it will not be in direct contact with water from the sprayhead. A pressure relief device (PRD) should be incorporated in the shower unit which is a safety feature designed to operate should an excessive build up of pressure occur within the shower (for example, if there is a blockage in the sprayplate).

In the unlikely event that the pressure relief device (PRD) activates it will eject water, so ensure the unit is positioned over the shower tray or a bath. If however, water does eject from the bottom of the unit, adjacent to the hose outlet, switch off the electricity to the shower at the double pole switch and turn off the water supply at the isolating stopvalve. Contact a qualified Electrician or Service Engineer for advice on replacing the pressure relief device (PRD).

To comply with water bylaws, the height of the shower should be such that when the sprayhead is hanging loose on the flexible hose, the sprayhose does not drop below the spill over level of the bath or shower tray which could lead to contamination. However, there may be installations when this requirement cannot be met. If the sprayhead can be placed within a bath, basin or shower tray, then a double check valve, or similar device, must be fitted in the supply pipework to prevent back-flow.

If in any doubt contact a Service Engineer, who will advise and supply a suitable device if required.

Plumbing connections

Plumbing to precede wiring

NOTE: The outlet of the shower acts as a vent and must not be connected to any tap or fitting not recommended by the manufacturer. Do not use jointing compounds on any pipe fittings for the installation. Do not use soldered fittings within the vicinity of the shower unit.

IMPORTANT: Before completing the connection of the water supply to the inlet of the shower, flush out the pipework to remove all system debris. This can be achieved by connecting a hose to the pipework and turning on the mains water supply for long enough to clear the debris to waste.

NOTE: An additional stopvalve (complying with water bylaws) must be fitted in the mains water supply to the shower as an independent means of isolating the water supply should maintenance or servicing be necessary.

Turn off the water supply either at the mains stopvalve or the isolating stopvalve (see Cutting off the water supply). Connect the mains water supply to the inlet of the shower via 15mm copper or stainless steel pipe using a 15mm x 15mm straight coupler or elbow compression fitting.


Refit backplate insert if removed, and secure with two fixing screws. If a side entry has been chosen this operation can be completed after connecting the electrical supply cable.

NOTE: If entry is from the rear, the conex nut fitting will be partially behind the surface of the wall.


This area must be left clear when plastering over the pipework in order to make the nut accessible for future adjustments. Do not use excessive force when making these connections. Ensure the backplate is square on the wall and tighten the two retaining screws which hold it to the wall. Turn on the mains water supply and check for leaks in the pipework connection to the shower.

NOTE: At this stage no water can flow through the shower.


Water too hot:

Not enough water flowing through the shower, check

- whether the sprayhead is blocked. Clean or replace sprayplate in sprayhead.

- increase the flow rate via the temperature control.

Increase in ambient water temperature, check

- flow rate. Select reduced power setting and re-adjust rate (via temperature control) to give required temperature.

Water too cool or cold:

Too much water flow, check

- flow rate. Reduce rate via the temperature control.

Water pressure below 1.0 bar (14.5 p.s.i.), check

- the low pressure indicator. If flag is red, continue with remainder of checks.

- If tank fed, re-plumb to mains water supply.

- If mains fed, ensure that mains stopvalve is fully open and that there are no other restrictions in the supply while shower is in use.

- Fit a pump to give minimum pressure of 1 bar (14.5 p.s.i.).

Water temperature cycling hot/cold at intervals:

Heater cycling on thermal cut-out, check

- Action required for ‘Water too hot’.

Shower varies from normal temperature to cold in use:

Water temperature has dropped below minimum required.

- Wait until the water pressure resumes to normal. This is sometimes shown by an indicator on the shower unit.

Pressure relief device has operated (water ejected from PRD (pressure relief device) tube):

Blocked sprayhead, check

- whether the blocked sprayhead can be cleaned or needs replacing. Fit a new PRD (pressure relief device).

Twisted/blocked flexible shower hose, check:

- Is there a clear passage through the hose? Replace the hose if necessary and fit a new PRD (pressure relief device).

Frozen heater can, check

- Is there evidence of freezing? Contact a Service Engineer for advice before fitting a new PRD.

Related Pages

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