How to install a pool heat pump
Updated: 21 October 2026
You have a unit in mind and the next job is the pipe between the filter and the pool. This is how to install a pool heat pump on the water side, and where you stop for an electrician. It is not a sizing table and not a bill. The five listings in the [pool heat pump comparison](/hub/pool-care/pool-heat-pump) do not state a flow, so this page cannot set a bypass for those ASINs. Peter F. used UK shop guidance and the wiring rules on 19 October 2026 and did not install a unit. A qualifying purchase can earn a commission at no extra cost to you.
You have a unit in mind and the next job is the pipe between the filter and the pool. This is how to install a pool heat pump on the water side, and where you stop for an electrician.
You have a unit in mind and the next job is the pipe between the filter and the pool. This is how to install a pool heat pump on the water side, and where you stop for an electrician. It is not a sizing table and not a bill. The five listings in the pool heat pump comparison do not state a flow, so this page cannot set a bypass for those ASINs. Peter F. used UK shop guidance and the wiring rules on 19 October 2026 and did not install a unit. A qualifying purchase can earn a commission at no extra cost to you.
Our top picks
| Badge | Product | Supply | Weight | Casing claim | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  JCKJWL JCKJWL 15 kW listing | not stated | 9 kg | Galvanised or steel | 5.8 | about £176.76 | View offer |
| Best value |  JCKJWL JCKJWL 9 kW variant | not stated | 9 kg | Galvanised or steel | 4.6 | about £163.00 | View offer |
| Alternative |  OUHFCASN OUHFCASN 18 kW 380 V | 380 V, also 220 V | not stated | not stated | 4.2 | about £154.44 | View offer |
On this page
Put it after the filter and before the chemicals
Pool water should meet the heat pump clean. Fit the heater on the return, after the filter and before any dosing. Chlorine, acid, shock and a salt cell belong downstream, where the treated water has mixed. HeatPumps4Pools states that sequence and pairs it with a bypass.
In UK pool work, 1.5 inch nominal pipe is the usual size, and hose tails on a plug-in mini are often 32 mm or 38 mm. A claim of no bypass describes that model’s flow range only. The five cheap listings print no band.
Set the bypass to about 1–2°C
A three-valve bypass isolates the heat pump and sets how much water passes through it. Too much flow and the water barely warms. Too little and the high limit trips. HeatPumps4Pools suggests about 1–2°C between water in and water out. Hayward’s UK notes say to open the bypass if the rise is too small, and close it if the rise is too large.
Measure after the unit has settled. If you cannot reach about 1–2°C inside the manual’s flow band, the pump and the heater do not match. Label the valves, because a winter drain uses the same handles. Hours and unit rates sit on the pool heat pump running costs page.
Give the fan free air and a solid base
The heat pump collects heat from the air its fan pulls across the evaporator. If that air is already the cold exhaust, output falls and the unit ices earlier. Leave a clear path in and out, on the side the manual names.
Stand the cabinet on a level slab. A documented plug-in around 26 kg, or a seasonal cabinet around 47 kg, needs a base for that mass. If the house is listed, in a conservation area, or already has an air-source heat pump, check planning before you rely on England’s Class G permitted development.
Stop at the electrics
Outdoor sockets up to 32 A need 30 mA RCD protection under BS 7671. A BS 1363 plug is 13 A at 230 V, about 3 kW. Anything above that is a new circuit, notifiable in England under Approved Document P.
Leave extension leads out. On an existing Great Britain property the Energy Networks Association expects every heat-pump load to be notified. The electrician can connect and notify within 28 days only if maximum demand stays at or below 60 A per phase. Otherwise they apply first. A 380 V title is an electrician’s supply, and opening the refrigerant circuit is F-gas work.
Drain it before a hard frost
Water left in the coil can crack the exchanger, and UK shop guidance treats that crack as outside the warranty. Before the first hard frost, isolate the heater on the bypass, open the drain the manual specifies, and empty the water side. Leave the filter path open so the pool can still circulate. Do not plumb a listing that leaves flow and voltage as not stated.
Common questions
Do I need a bypass?
You need a three-valve bypass when filter flow can exceed the heat pump’s range, and you need those valves for service and for winter. HeatPumps4Pools treats the bypass as part of a normal install and pairs it with a 1–2°C rise. A plug-in claim of no bypass describes that model’s own band. The five listings here do not state a flow, so they do not earn that exception.
What temperature rise should I set?
Aim for about 1–2°C between water in and water out, with the filter at normal flow. If the rise is too small, too much water is passing through. Hayward’s direction is to open the bypass when the rise is too small and close it when the rise is too large. Follow the manual if its limits differ. A large jump across the coil is not the target this guidance describes.
Where do chlorine and salt cells go?
Downstream of the heat pump, after the filter and the heater, so dosing happens in water that has left the coil. A salt cell or doser upstream puts concentrated chemical through the exchanger. Titanium tolerates salt water better than stainless steel, and it still wants diluted water. A listing that never says titanium is a weak choice for a salt pool.
When is an electrician required?
An electrician is required for a new circuit, for anything above a 13 A plug, for a 380 V title, and whenever the main fuse might not take the load. In England that new circuit is notifiable under Part P. You can do the unions and the bypass if you are competent with the pipe. The consumer unit and the refrigerant circuit stay closed.
Do I have to tell the network operator?
On an existing Great Britain property, the Energy Networks Association says every heat-pump load is notified. The electrician can connect and notify within 28 days if maximum demand stays at or below 60 A per phase and the supply is adequate. Above that, they apply first. Northern Ireland sits outside that Great Britain process, so the electrician uses the local operator.
How do I leave it over winter?
Isolate the heater on the bypass and drain the water side before a hard frost. Ice damage to the exchanger is widely excluded from warranty. Keep the filter path open if your winter plan still circulates the pool. Follow the manual for the valves and for any minimum temperature. A cover cuts the heat you would otherwise be replacing, which is separate from emptying the coil.
Related pages
Sources
Public UK sources for seasonal COP, grants, electrical rules and running cost, taken from the research digest. Listing prices, stars and review counts are from amazon.co.uk on 19 October 2026.
- Ofgem — Energy price cap, 1 October to 31 December 2026 (retrieved 19 October 2026)
- Boiler Upgrade Scheme Regulations 2022, regulation 9 (retrieved 19 October 2026)
- GPDO 2015, Class G — air source heat pumps (retrieved 19 October 2026)
- Approved Document P — electrical safety in dwellings (retrieved 19 October 2026)
- IET Wiring Matters — BS 7671 regulation 411.3.3 and 30 mA RCDs (retrieved 19 October 2026)
- GOV.UK — qualifications required to work on F-gas equipment (retrieved 19 October 2026)
- SPATA — swimming pool heating factsheet (retrieved 19 October 2026)
- Calorex 2025 inverter heat pump brochure (retrieved 19 October 2026)