When people first look into getting a swimming pool heat pump they are often somewhat incredulous. After all, not everyone is familiar with the technology and what it can do, which tends to give rise to some serious misconceptions that many of us have before we look into the subject in detail.

”How can a tiny heat pump get my swimming pool up to temperature?” they ask.

It’s completely understandable because the volume of water that needs to be heated is far bigger than the typical house’s domestic hot water tank. It does seem rather a big ask, particularly when there is a lot of information out there saying that heat pumps are less efficient when it comes to heating hot water for use in the home.

However, there are some important considerations that work in favour of the heat pump option.

Firstly, your swimming pool doesn’t need to be heated to as high a temperature as your domestic hot water. You won’t be washing dishes in it, or dipping a bucket into it for disinfecting your kitchen floor, so the temperature can be a lot lower. Besides, it is far more comfortable to have your pool at a typical “swimming temperature” rather than the temperature of a hot bath. If you’ve ever been for a swim in a pool that’s too hot you’ll know just how uncomfortable that can get!

This lower temperature allows the heat pump to operate much more efficiently and makes the use of heat pumps for swimming pools a viable option. This is a similar to underfloor heating, which people tend to be more familiar with, whereby the much larger floor area (compared with a traditional radiator) allows the house to be heated to a comfortable temperature despite the water in the underfloor heating system being cooler than in a traditional radiator.

So How Does a Heat Pump Work For a Swimming Pool?

The short answer is, “The same as for any other application”. Heat pumps work by moving heat from a warmer location to a cooler location. In the case of a ground source heat pump for a swimming pool, this would be moving heat from the ground loop buried in the garden adjacent to the pool and transferring it to the water in the pool.

It is possible for heat pumps to generate up to 7 times more heat energy than they consume during their normal operation. This is at the very top end of the range and relies on a large temperature difference between the warm side and the cold side, but it shows what can be achieved.

For more information about how heat pumps work, check out our introduction to heat pumps, which gives a more detailed explanation.

Will the chlorine in my pool (or salt) cause harm to my heat pump?

Many heat pumps are designed to work under such conditions, sometimes using titanium, or other metals that are highly resistant to corrosion, in the heat exchangers. Provided you choose a good quality pump that is designed for your particular application, you shouldn’t need to worry about damaging it.

For indoor pools, Is it better to put the heat pump inside where it can reduce the humidity of the pool room and warm the pool water as well?

One possible configuration of this kind of system could be to have the heat pump blowing its exhaust air out through a vent in the wall of the building. The air intake should be at the opposite side of the building and could be a simple vent.

While this is possible, and on the face of it might seem more efficient, it would actually result in a problem. Although the heat pump would be using warmer air, which has obvious efficiency benefits, after a time, the air in the building would end up being the same temperature as the air outside, which could be very cold during the winter months.

In most cases, it would be better to locate the heat pump outside and dehumidify using separate dehumidifiers installed inside the pool room. You would then be able to control the temperature of the pool water and the air in the building independently, which is obviously much better.

Always use a solar cover over your pool when heating your pool using a heat pump

In the same way that good home insulation is important for heating your house with a heat pump, you should always use a solar cover on a pool that is heated in this way. Not only does it have the capability to warm your pool up by as much as 8 degrees Celsius, but it also cuts down on evaporation, heat loss and chemical consumption, as well as preventing leaves from getting into your pool.

With a solar cover, you will be able to heat your pool more cheaply and reduce the impact you are having on the environment due to energy consumption and chemical usage. Covering the pool at night is especially important because the colder night air will cool down your pool more quickly.

Heat Pump Installation

Installing an air-source heat pump is pretty straightforward. It needs a level, hard standing base which can be as simple as a concrete slab, an electricity supply and any associated pipework. These days plumbing it in will be straightforward with “push-fit” pipes and connectors but you should always obtain the services of a qualified electrician to connect up the power supply, particularly as this will often need to be a 3-phase supply which is higher voltage.

What size heat pump do I need to heat my swimming pool?

The size of unit you require will depend on several factors, including whether you pool is inside or outside, in a windy or sheltered spot, whether you’ll be using your pool during the winter or summer, whether it has a cover and, of course, how big it is.

It is generally better to oversize the heat pump because this means the pump will heat up your pool more quickly, which is an important consideration when heating up initially for that first dip in the spring after the long winter chill.

Conversely, if your pump is too small, you’ll end up never getting your pool up to temperature, no matter how long you run the heat pump for.

Always get advice from a qualified professional on what size of heat pump you require, and err on the larger side to be safe.