How to Connect a Heat Pump to a Hot Tub
Three valves join a heat pump to your hot tub.
The heat pump connects into the hot tub's pipework after the filter, through a bypass. One half-open valve sends part of the water through the heat pump, and a valve on each side of it lets you shut it off. It runs on its own outdoor power supply.1
Where the heat pump goes
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Outside, on firm level ground
Ideally a level concrete base strong enough for the unit's weight, close to the hot tub and easy to reach for maintenance.1
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Room to breathe
Leave 1 metre clear in front of the fan, 50 cm at the sides and back, and nothing above it.1
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Thought for the neighbours
Point the air outlet away from neighbouring windows and towards the side of the garden least sensitive to noise. Our 7kW runs at 54 dB(A) and our 12kW at 55 dB(A).1
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Somewhere for water to drain
A heat pump makes condensation, so it needs a drain or soakaway close by. It can be raised on mounting pads, and anti-vibration pads under its feet cut the noise further.1
The pipe connection: a bypass
The heat pump is connected through a bypass, three valves that control how much water goes through it.1 The valve on the main pipe between the two connections is set half open, so part of the flow turns off through the heat pump and the rest carries on. The valves on the heat pump's inlet and outlet are fully open while it runs, and closed when you need to work on it, without stopping the hot tub.
After the filter
The water reaching the heat pump should already have been filtered, so keep the hot tub's filter clean. Any automatic dosing goes after the heat pump, on the return to the tub.1
Gluing the PVC pipes
A bypass is built from PVC pipe and fittings joined with solvent adhesive. The steps below follow our installation manual.1
Cut the pipe square
Cut the PVC pipe with a saw, straight across. An angled cut leaves a gap in the joint.
Dry fit first
Put the whole bypass together without glue to check every piece fits, then take it apart.
Chamfer the ends
Take the sharp edge off each cut end with sandpaper.
Clean and glue
Wipe PVC cleaner (stripper) on both ends to be joined, then apply PVC adhesive to the same places.
Assemble and wipe
Push the joints together and wipe off any adhesive left on the outside of the pipe.
Wait two hours
Leave the adhesive to dry for at least two hours before any water runs through the pipes.
The power supply
A heat pump runs on its own single phase 220 to 240V supply, never an extension lead.1 The circuit needs a 30mA RCD, a D-curve breaker sized for the model, an outdoor-rated cable, and an isolator close to the unit so it can be switched off for maintenance. It shares the same earth as the hot tub.1
Have the supply fitted by a qualified electrician. Our hot tub electrical installation guide explains what to ask for.
The first start
Let it settle
A heat pump should always be stored and moved upright. If it has been laid on its side, stand it upright for 24 hours before starting it, to protect the compressor.1
Then set the temperature
Open the inlet and outlet valves, set the bypass valve half open and switch on at the control panel. It heats the water to anywhere from 15°C to 40°C, and after switching it off, give it 3 minutes before turning it on again.1
Our heat pumps
Both come with kerbside delivery for £25, in 1 to 2 days.3 See all our air source heat pumps, or read what size heat pump you need.
Outdoor Living 7kW air source heat pump
£1,699
For most hot tubs. 50mm water connections, 8A at most on a 16A D-curve breaker, and 831 x 393 x 654 mm.1, 2
Outdoor Living 12kW air source heat pump
£2,199
For swim spas and large hot tubs. The same 50mm connections and size, 13A at most on a 25A D-curve breaker.1, 2
Fitting questions
Open a question to read the answer. The step by step diagrams are in the installation manual for our 7kW and 12kW heat pumps.
How do you connect a heat pump to a hot tub?
It joins the hot tub's pipework after the filter, through a bypass of three valves. A half-open valve on the main pipe sends part of the water through the heat pump and back, and a valve on each heat pump connection lets you shut it off for maintenance. Our heat pumps have 50mm water connections.
Where should a hot tub heat pump go?
Outside, on firm level ground such as a concrete base, close to the hot tub. Leave 1 metre clear in front of the fan, 50 cm at the sides and back, and nothing above it. Point the air outlet away from neighbours' windows, and keep it out of reach of children.
Can I plug a heat pump into a normal socket?
Connect it to its own outdoor supply, never an extension lead. It needs a 30mA RCD, a D-curve breaker of 16A for our 7kW or 25A for our 12kW, and an isolator close to the unit, all fitted by a qualified electrician.
How long after fitting can I turn the heat pump on?
Wait at least two hours after gluing the pipes before water runs through them. If the heat pump was laid on its side in transit, stand it upright for 24 hours before starting it.
Who should fit a hot tub heat pump?
A qualified engineer for the pipework and a qualified electrician for the power supply. Our installation manual walks through each step so you know what to expect.
Sources
- Outdoor Living, Hot tub and swim spa air source heat pump user and installation manual, OLHP07 and OLHP13: safety instructions, installation (location, layout, hydraulic connection, electrical installation) and technical data, version V20221221.
- Outdoor Living, product pages for the 7kW and 12kW air source heat pumps, accessed October 2026.
- Outdoor Living, air source heat pump delivery options, accessed October 2026.
Paul Margerison
Managing Director & Founder, Outdoor Living
Fitted well, a heat pump is the quietest upgrade a hot tub can have. Plan the spot, the pipes and the power before it arrives and the day itself is simple.