Video by Skill Builder. This guide draws on "Installing Bristan Electric showers with Roger Bisby" from the Skill Builder channel. Roger Bisby is one of the UK’s most experienced building and trade commentators and the video is a proper, no-nonsense walk-through of the installation process — including the key point about covering the existing footprint to avoid re-tiling. Worth watching before you buy anything, particularly the explanation of the cold supply connection and the water entry gland.
1. Choose the right kilowatt rating
Electric showers come in 7.5kW, 8.5kW, 9.5kW, and 10.5kW versions. A higher rating heats the water faster and gives a better shower flow at lower mains pressure. In the UK, 8.5kW or 9.5kW suits most homes with normal mains pressure.
Check your consumer unit (fuse box) has a spare circuit capacity. A 9.5kW shower needs a dedicated 45-amp circuit, and a 10.5kW shower needs a 50-amp circuit. If neither is available, a qualified electrician will need to assess whether the board can take an additional circuit.
2. Turn off water and electricity at the mains
Isolate the cold water supply at the mains stopcock or at the isolating valve on the pipe running to the shower. Open a tap downstairs to confirm the water is off. Then turn off the electricity at the consumer unit. Put a note on the consumer unit while you work — just in case.
If you are replacing an existing electric shower, note how the old unit was plumbed and wired before removing it. Photograph the connections if it helps.
3. Fix the shower unit to the wall
Open the shower unit and remove the front cover. Mark the fixing holes on the wall in pencil, check plumb with a spirit level, and drill. Use appropriate fixings for the wall type — ceramic tiles over plasterboard need cavity fixings; tiles over solid plaster or block take standard plugs.
Thread the water pipe and cable entries through the correct knockouts in the back of the unit before fixing it to the wall. Most modern units have multiple entry points to accommodate different pipe and cable approaches.
4. Connect the cold water supply
The cold mains connection is straightforward plumbing: a 15mm copper or plastic push-fit pipe runs to the unit’s inlet, with an inline isolating valve so you can service the unit in the future without turning off the whole house. The manufacturer’s instructions will show the correct connection point and specify whether a pressure-reducing valve is needed at high mains pressure.
Use PTFE tape on any threaded connections and tighten firmly but not aggressively. Turn the water back on briefly to check for drips before closing everything up.
5. The electrical connection — this requires a qualified electrician
Fitting an electric shower requires a new dedicated circuit from the consumer unit: 10mm² twin and earth cable, protected by a 45A (or 50A) RCD-protected breaker, run in conduit or chased into the wall. This work is notifiable under Part P of the Building Regulations. That means it must be carried out or certified by a qualified electrician — either a registered Part P competent person, or inspected and certified by Building Control after the fact.
The electrician will also fit the shower’s pull-cord ceiling switch (required in bathrooms, where wall switches are not permitted near water), correctly bond any exposed metal pipework, and issue a Minor Works Certificate on completion. Keep that certificate — you will need it when you sell the property.
6. Make the internal connections and reassemble
Once the electrician has run the cable to the unit, the final connections inside the shower are made following the wiring diagram in the installation booklet. Live, neutral, and earth terminals are clearly marked. The cable is secured through the gland to take strain off the terminals.
Refit the cover, restore the water supply, and switch the electricity back on. Set the shower to the coldest setting and run it briefly to check flow and confirm there are no drips from the water connections.
7. Test and check the earthing
Your electrician should carry out continuity and insulation resistance tests before signing off the work. Check that the pull-cord switch operates correctly and that the RCD on the new circuit trips when tested. Do not use the shower until the electrical sign-off is complete.
When to call a handyman
Richard can handle the plumbing side — disconnecting the old unit, making the cold water connection, and fitting the shower itself to the wall. The electrical circuit and certification must be done by a qualified Part P electrician. Richard can coordinate both trades for you if needed, or advise whether a like-for-like replacement on an existing circuit requires the same level of sign-off.
Need a shower fitted or replaced?
The Sandwich Handyman can handle the plumbing and installation for electric, mixer, and power showers in Sandwich, Kent — and can coordinate the electrical certification through a registered electrician.
Contact Richard