Inspired by a helpful YouTube guide. This walk-through is based on the popular UK video “ALL ABOUT SHOWER PUMPS — Plumbing Tips” from the plumberparts channel, which covers everything from how twin-impeller pumps work to the common installation mistakes that cause noise and airlocks. Worth watching before you order anything — you will quickly see whether your system actually needs a pump and which type to buy.
1. Check whether your system can take a pump
Shower pumps only work on gravity-fed systems with a separate hot water cylinder and a cold water storage tank in the loft. If you have a combi boiler, a pump will not help — the pressure comes from the mains, not gravity, and adding a pump will cause serious problems.
Look in your airing cupboard. A copper cylinder with an immersion heater and pipework going up into the loft is a good sign. No cylinder means combi — stop here and call a plumber about other options.
2. Choose the right pump
Twin impeller pumps boost both hot and cold supplies independently, which keeps the water temperature stable. Single impeller pumps only boost one side. For a shower, a twin impeller model is almost always the better choice.
Bar ratings of 1.5 to 2.0 are usually enough for an average UK home. More bar does not always mean better — too much pressure can strain older pipework and fittings. Match the pump to your actual needs rather than buying the biggest one on the shelf.
3. Fit a Surrey or Essex flange on the cylinder
A Surrey flange screws into the top of the hot water cylinder and draws water from below the air layer that collects at the top. This prevents air being sucked into the pump and causing airlocks or noise.
An Essex flange does the same job but fits into the side of the cylinder below the waterline. Which one you use depends on the cylinder type and what access you have. Turn off the water supply, drain down the relevant section, and fit the flange before doing anything else.
4. Position the pump correctly
The pump must sit below the water level in the cold tank. Most people put it on a shelf in the airing cupboard. Leave enough space around it for air to circulate — these things generate heat when running.
Stand it on a rubber mat or vibration-damping feet to reduce noise transmission through the floor. That said, even a well-installed pump will hum. If yours is rattling, something is loose or there is air in the system.
5. Connect the hot and cold inlets
Run 22 mm pipe from the flange on the cylinder to the hot inlet on the pump, and from a dedicated cold supply off the storage tank to the cold inlet. Do not tee off existing shower supply pipes — the pump needs dedicated feeds so it draws at the right rate.
Fit isolating valves on both inlets so you can service the pump without draining the whole system. These are invaluable the first time you need to swap a pump out.
6. Connect the outlet to the shower
From the pump outlets, run pipe up to the shower valve. Keep pipe runs as short and direct as possible to minimise pressure losses. Use push-fit or compression fittings — either is fine, but make sure every joint is sound before covering anything up.
Avoid sharp bends where you can. Long sweeping bends keep the flow smooth and reduce the chance of airlocks forming later.
7. Wire the pump through a fused spur
Shower pumps must be wired through a fused connection unit with a 3-amp fuse, switched off outside the bathroom to meet Part P regulations. The pump itself should be outside any bathroom zone — which is why the airing cupboard is the usual location.
If you are not confident with electrical work, get a registered electrician to wire it. The mechanical side is DIY-friendly. The wiring side is where mistakes cause serious problems.
8. Fill, test, and bleed for airlocks
Turn the water back on slowly and let everything fill up before switching the pump on. Then turn the shower on at the valve before switching the pump on at the fused spur. This prevents the pump running dry, which can damage the impeller.
If the shower sputters or the pump sounds strained, air is trapped somewhere. Turn the pump off, run the shower at low flow to purge the air, then try again. Most airlocks clear within a minute or two.
When to call a handyman
Call Richard if the flange installation is proving awkward, the pipework route is complicated, or you want someone to wire the fused spur and test the circuit properly. Shower pump work is satisfying when it goes well — and infuriating when there is a hidden airlock you cannot track down.
Need plumbing or maintenance help?
The Sandwich Handyman can help with plumbing maintenance, bathroom fitting, and property upkeep around your home in Sandwich, Kent.
Contact Richard