Pool Heat Pump Installation Tips

This article outlines our pool heat pump installation tips for the best practice way to install your swimming pool heat pump.

Installing your pool heat pump is a fairly simple task and can be completed either by the pool owner, a local engineer or by one of our experienced installation engineers. The manufacturer’s recommendations should however always be followed in order not to invalidate the warranty, or to prevent your heat pump from working properly.

If you would like us to install the heat pump for you, please contact us for an installation quote.

Here are some tips if you decide to install a pool heat pump yourself:-

The heat pump requires:-

1. A Suitable Location

Choose a location for your heat pump where it can get a good flow of air. Optimum efficiency of the heat pump relies on good air flow.

Where possible the heat pump should always be installed outdoors so it can receive a good supply of fresh air to operate and extract the heat from.

pool heat pump layout-diagram.jpg

Minimum clearances for horizontal fan heat pumps shown above


Minimum clearances for vertical fan heat pumps shown above

Make sure that the air being expelled by the fan will not hit any obstacles and could be recirculated back into the heat pump.


Pool heat pumps, come in two main formats – vertical fan and horizontal fan models. Vertical fan models will draw air in at the sides of the heat pump and blow cooler air upwards out of the top of the unit. You should ensure that there are no obstructions above the heat pump that could cause the expelled air to recirculate back into the unit as this will reduce its efficiency, eg low hanging trees or roofs etc.

Similarly horizontal fan models will draw air in at the back of the unit and blow out colder air from the front of the heat pump. More space is better, but as a minimum, you should allow 300mm behind the heat pump and 2 metres in front of it. Again, the expelled air should be able to blow away without hitting obstructions eg hedges, fences etc which could cause the air to re-circulate.

Vertical fan models should have at least 2 feet (600mm) clearance around the sides and no obstructions above as per the diagram below.

Minimum Clearance Requirements

space reqd

Duratech Type Heat Pump Required Clearances

Pool heat pumps should wherever possible be installed outdoors in order to have a good supply of fresh air. However some can be installed inside a pump house – see the section below.

Try to locate the heat pump close to the pool pump to minimise the friction in the pipes. If your pipe run is too long, you may have an insufficient water flow rate through the heat pump and may need to upgrade your pool pump or use larger diameter pipes to and from the heat pump to reduce friction in the pipes and maintain a good water flow rate.

Most heat pumps state the nominal water flow required on their specification charts. If the water flow through the heat pump is too low, then the heat pump may overheat and the safety mechanism will turn the unit off.

Not Like This  – Hall of Shame !

Some examples of incorrect swimming pool heat pump installations.

insufficient heat pump clearance pic1insufficient heat pump clearance pic2
Insufficient Clearances on 3-sides of heat pumpInsufficient clearances for air-flow
insufficient heat pump clearanceheat pump installed the wrong way round !
Insufficient clearance at front – should be at least 2.5m. Heat pump is wrong way round !Insufficient clearance – Heat pump blowing onto shed
No clearancepond-heat-pump-under-decking-pic2.jpg
Insufficient clearance – should be at least 2.5m at front and 300mm at backHeat pump installed under decking. Risk of air recirculation and insufficient air flow
Calorex heat pump installed inside a shed but the wrong way round ! Should blow to the outside, not inside the shed. Also fan blowing onto an obstructionHeat pump is installed the wrong way round, is blowing onto the wall ! It should have a minimum of 2.5m clearance in front of the fan.


To see examples of heat pumps installed correctly, please see our Photo Gallery

2. Water Flow Rate

Most of our pool heat pumps state the required water flow rate on their specifications table. If the water flow rate is too low, then the water in the heat pump will overheat and the heat pump will switch off.

Check the water flow rate from your pool pump and through your filter to ensure that it is high enough for your pool heat pump.

Note that there is a maximum possible flow through each size of pool pipe regardless of the power of your pump. For larger heat pumps it may not be possible to achieve sufficient water flow through small pipes (eg 1.5″ pipes). Please contact us for advice on this.

We sell water flow meters that will show you the flow rate through your pipes.

See our “Accessories” section

You should also regularly backwash your pool filter to ensure that the water flow rate remains at an adequate level.

3. Base

The base for the heat pump should be level and sound. You can use either a concrete base, paving slabs laid on sand or timber decking.

The vibration from the heat pump will be fairly minimal and will not disturb the paving slabs.

The heat pump can be installed above or below water level. The only proviso is that the pool circulation pump is powerful enough to deliver the water flow rate that the heat pump needs to operate.

We also sell mounting feet and lightweight slabs to mount the heat pump on. These help to raise the heat pump off the ground and also reduce noise and vibration


While the heat pump is operating, it is normal for condensation water to drip from it – particularly in humid conditions. You should consider the condensate water that will come from the unit in the base design as the amount of water can be considerable and cause a pool of water to form. For example if the unit is mounted on timber decking, holes can be made in the decking to allow the condensate water to drain away and not cause rotting to the timber.

Some heat pumps have a water outlet tube that will channel the condensate water away, or a piece of hose can be attached to it to divert the water to a specific location.

Some customers mistakenly think that the heat pump has a leak when in fact the water coming from the heat pump is normal condensation

4. Electrical Supply

Before purchasing a pool heat pump, you should check the running current and peak current stated on the listing for your desired model.

Ensure that your electrical supply is adequate to support the running and startup currents for the unit.

It is normally recommended to run a dedicated cable back to your electrical consumer unit for the heat pump and install a dedicated breaker for the heat pump.

Most heat pumps will have a higher electrical current demand when they start. This only lasts for a millisecond or so while the compressor starts and the current then reverts to the normal running current for the unit.

The size of circuit breaker required is normally stated on the listing for each heat pump and is normally slightly larger than the startup current.

You would normally use a type “D” circuit breaker (fuse) with your heat pump. The type “D” circuit breaker allows for the higher current at startup (as the compressor starts) without tripping the breaker.

If you have a very “sensitive” electrical supply, then some heat pumps have an optional (or built in) “soft-start” option. The soft-start option “eases” in the startup current up to the running current to avoid a power spike on startup.

The soft-start kit/option is normally only required for installations using a large single phase heat pump (eg 30kw) with a limited or sensitive electrical supply. In extreme situations, the house lights may flicker or the circuit breaker trips when the heat pump starts up. The soft-start kit helps to prevent this.

The soft-start option is not normally required in the UK, or on small heat pumps or on 3-phase heat pumps. Please contact us for further information.

We sell a third-party soft start module that can be added to virtually any heat pump. This is listed under our “Accessories” section

Armoured cable is normally used to supply the heat pump. This is to prevent the cable from being accidentally damaged (eg by digging through it with a spade)

The size (thickness) of the cable required depends on the length of cable used. A longer cable run will require a thicker cable due to the increased resistance of the long cable.

The armoured cable should be run to a rotary isolator switch which should be located within 1-meter of the heat pump to allow the power to be easily killed to the heat pump

The electrical work should be completed by a qualified electrician who can calculate the cable size required.

The heat pump must also be properly earthed.

As the heat pump is outdoors, the electrical circuit should also be protected by an RCD

Most properties have a single-phase electrical supply. 3-phase electrical supply is normally only found on larger properties or on commercial installations. If you are not sure, you probably have a single phase electrical supply, but ask your electrician to confirm this for you.

Single phase supplies operate at around 230-240v in the UK and have one live wire, neutral and earth and are the most common type of power in domestic properties.

Larger properties may have a 3-phase power supply. This typically operates around 380-415v and uses three live wires, a neutral and earth wires.

Note that most 3-phase installations are 380v-415v, however in France it is possible to find both 380v-415v and some older 220v 3-phase supplies, so please check which type you have before ordering.

All of our heat pumps are manufactured to work with 50hz electrical supplies (which are used throughout Europe)

Note that in the USA, they use a 60hz electrical supply. USA specification heat pumps will not work in the UK or Europe. All of our heat pumps are made to use a 50hz electrical supply.

We can supply an electrical connection box with a built in timer for your pool pump – see our “Accessories” section

The electrical control boxes can be custom designed  to your requirements. Please contact us for a quote.

5. Plumbing

It is easy to add a heat pump to an existing pool pipework system.

First check to see what size of pipes you have.

In the UK, these are normally 1.5″ or 2″ pipes. In Europe, 50mm is more common. Check the writing stamped on your existing pipes and elbows to see which size you have. Do not just measure the external diameter of the pipes or fittings as this is often different to the size required and you may accidentally order the wrong size pipe and pipe fittings !

eg 1.5″ pool pipe measures approx 1.9″ external diameter (the 1.5″ refers to the internal diameter of the pipes for imperial sizes and the external diameter for metric sizes)

Once you know the existing pipe size that you have, you will know what size connectors and elbows you will need.

In the UK 1.5″ pipes are the most common and 50mm in Europe.

Please see our Accessories section for a catalogue of pipe fittings.

If you have an existing pool heater eg gas or oil boiler, then if it still works ok, we recommend that you leave it in place and put the heat pump in line with the existing boiler.

This will allow you to run both the heat pump and boiler if required for a rapid pool heat up. The old heater can also help to supplement the heat from your heat pump in very cold weather to help extend the swimming season.

Where possible the water should run through the heat pump first and then the existing heater so that the heat pump does most of the heating work. The thermostat on the existing heater (eg gas boiler) can be set lower than the heat pump so that the existing heater will only operate if required.

There are only two pipes to the heat pump – a “flow” and a “return” pipe.

We recommend that you install a “bypass” arrangement with your heat pump

The bypass is a series of 3-valves. These allow you to isolate the heat pump to prevent water flowing through it.

A bypass can also allow the water flow rate to be adjusted to achieve the optimum performance for the heat pump. We are happy to advise on how to adjust the flow rate accordingly depending on the make and model of heat pump used.

Generally, you should aim for a difference between water in and water out temperatures of around 1-2 degrees

We sell bypass kits under our Accessories section

This is required in winter when you need to drain all water from the heat pump to prevent damage by freezing, however you may have a frost stat on your pool pump and may wish to continue to circulate the water round your pool pipes.

The bypass setup also allows you to adjust the water flow rate passing though our heat pump. By slghtly opening the bypass valve, you can reduce the water flow through the heat pump.


Bypass Valve arrangements


You must not allow water to freeze inside the heat pump during winter as this can crack the heat exchanger and frost/freezing damage is generally not covered by the manufacturer’s warranty. We sell a range of winter covers for pool heat pumps to protect your unit – see our Accessories section

The pipes to and from the heat pump can be insulated to help reduce heat loss.

The heat pump is normally installed as the last item in the water flow before the water returns to the pool, ie after the filter.

The only exception to this is if you have a chlorination unit in which case this should be the last item before the water returns to the pool so that concentrated chlorine does not go through the heat pump as this could cause premature corrosion to the heat exchanger.

The heat pump can be installed alongside any existing heater that you have (eg gas heater). This allows you to use the gas heater as well as the heat pump if required either to rapidly heat up the pool or if the air temperature is too cold to run the heat pump efficiently eg at the and of the swimming season.

Try to have the water going through the heat pump first and then the gas/oil heater so that the heat pump does most of the heating work and the existing boiler only needs to “top-up” the temperature

Typical pool heat pump setup


6. Multiple Heat Pumps

For large pools, it is possible to run two heat pumps together

Two heat pumps working together

or even larger pools can use four heat pumps

Four pool heat pump configuration

Multiple heat pumps can be plumbed in series or in parallel. Please contact us for advice on the best method to use for your situation.

7. Indoor Heat Pump Installations

Where possible a heat pump should always be installed outdoors as they need a constant supply of fresh air to operate and extract the heat from. However it is possible to install some models inside the plant room. For vertical fan models, ducting can be constructed to to vent the expelled air out through the wall of the building.

For horizontal fan models, they can be placed up against the wall and a hole cut through the wall in line with the fan to allow the expelled air to escape to the outside.

Recirculation of the expelled air back into the heat pump must be avoided.

For indoor installations, it is also necessary to allow air to enter the pump house. A vented door or grille should be installed at the opposite side of the pump house which is sufficiently large to allow fresh air to enter the room at the same rate that it is leaving the room.

For indoor pools, placing the heat pump inside the pool building can help to dehumidify the air by drawing fresh air into the pool room and using the heat pump to expel the humid air.

The disadvantage of this arrangement is that the air temperature inside the pool room will soon be reduced to the same as the outside air temperature. For indoor pools, this may not be desirable and some sort of air heating may then be required negating the benefit of locating the heat pump indoors.

Waterco indoor vent kitCompetition through the wall kit
Ducting of a vertical fan heat pump to outdoorsInstallation of a horizontal fan heat pump in a plant room


8. Indoor Pools

Indoor pools have different requirements to outdoor pools, the main difference being the need to dehumidify the moist air and also to heat the air in winter.

Normally for indoor pools, the air temperature should be 1 degree warmer than the pool water. eg pool water = 28c, air temp = 29c.

For indoor pools, we do sell an all in one unit from Heatstar or Calorex that provides air heating, air dehumidification, fresh air inlet and pool water heating. Please contact us for details.

There are two main options for indoor pools:-

  1. Pool heat pump and separate free-standing or wall mounted dehumidifiers. The dehumidifiers can have built in electric heaters to warm the pool room air in winter.
  2. All in one unit providing air heating, air dehumidification, fresh air inlet and pool water heating. These units need ducting to blow the dehimidified air over any glass windows to prevent condensation from forming.
calorex vaporex dehumidifier
Heatstar Gemini – All in one unitCalorex Vaporex free-standing air dehumidifier


We can also design a system which is powered by an domestic type air source heat pump, feeding a buffer tank



We offer an indoor pool design service to help select and specify all of the equipment for indoor pools

See our Indoor Pools page for more information

9. Heat Pumps for Hot Tubs and Swim Spas

Our heat pumps can also be installed on hot tubs and swim spas.

Using a heat pump will normally give greatly reduced running costs compared to an electric heater and the use of heat pump on spas and hot tubs is becoming increasingly popular.

The desired water temperature can be set to a maximum of +40c


The heat pump is simply plumbed into the existing spa circuit

We recommend that the existing electric heater is retained as a backup heater to the heat pump for extremely cold (sub-zero) air temperatures

Ideally the water should flow through the heat pump first and then the electric heater second.

Please contact us if you would like any advice on incorporating a heat pump onto a hot tub or swim spa.

10. Installation Examples

Below are some pictures taken from our Photo Gallery of installations made using heat pumps supplied by HeatPumps4Pools

Heat Perfector Installation in Essex UKHeat Perfector Plumbing Arrangement Example
Heat Perfector 20kw Installation in Essex UK. Unit installed on paving slabs. Pipework insulated. Existing pipework extended out of poolhouse to heat pump.Plumbing Arrangement – note bypass valve system to allow the unit to be isolated and drained down in the winter
Heat Siphon in South of France 2009Heat Perfector 32kw
Heat Siphon unit installed in the South of France in 2009.
Heat Perfector 32kw unit


To see other installation examples, please see our Photo Gallery

For further tips on installing a heat pump, please also see our FAQ page

11. Installation Service – Let us install it for you

We offer a full installation service for pool heat pumps using our fully qualified engineers.

Our engineers are qualified electricians and experienced heat pump engineers that will install your heat pump in accordance with the manufacturer’s instructions.

We can install heat pumps throughout most areas of the UK

Please contact us for an installation quotation

12. Queries?

If you have any queries on installing your heat pump, then please contact us at enquiries@heatpumps4pools.com 

Or please use our online chat facility