Many leisure centres, gyms, holiday parks and hotels have swimming pools, requiring thousands of liters of water. Although filling these swimming pools is important, it’s equally as vital that they are warm and comfortable for guests or members to swim in.

In commercial settings, adequate management of water heating is needed, with commercial boiler systems being fitted and utilised to heat water up quickly and efficiently to match the needs of the business and those interested in using their services. For a swimming pool to be used, warm water is vital, but how exactly is a commercial swimming pool heated?

How do you heat a swimming pool?

There are several ways of heating both domestic and commercial swimming pools. Heat pumps are a popular option that make it possible for cold water to be converted into warm water. Alternatively, solar panels are growing in popularity for powering homes and business. However, as they’re rarely effective enough to power swimming pool heating in cooler climates, it’s likely that they’ll solely remain an option for warmer parts of the world.

Boilers are the most common component for heating a swimming pool, with the option to heat water by having it pass through the boiler or the water heating separately using an external heat exchanger. A commercial boiler can be situated either outdoors or indoors and is powered by natural or propane gas.

Steps a boiler goes through to heat a swimming pool are as follows:

  1. Cold water fills the pool
  2. The water is pumped out of it using a pump
  3. It then passes through a filter and is sent to a heater
  4. Gas is burned in a combustion chamber
  5. The heat from the chamber is passed onto the water
  6. Warm water is returned to the pool
  7. This entire process happens continuously to maintain a flow of warm water
How do you heat a swimming pool

How to size a boiler for a swimming pool

Swimming pools come in different shapes and sizes, and the boiler used to heat the swimming pool needs to be capable of doing so in a quick and effective manner. The size of the boiler will primarily be based on the size of the pool and how much water needs to be heated.

Estimate pool size in relation to boiler size:

Pool size (length x width)Required litres of waterBoiler size (min to max in kW)
24 x 12ft32,0009-14
26 x 13ft37,0009-14
28 x 14ft44,0009-29
30 x 15ft51,00014-29
32 x 16ft57,00029

How long does it take to heat up a swimming pool?

The period of time needed to heat up a swimming pool will vary based on size of the pool, the amount of water being heated and the equipment being used. For example, a pool is likely to heat up quicker if it’s smaller, the boiler being used is larger or more efficient or if a heat pump is being used. However, on average, the type of swimming pool that you would find in a leisure centre or gym being heated by a standard commercial boiler would typically take between one and two days to be completely heated up.

How much does a heated swimming pool cost?

When it comes to calculating the potential cost of heating a swimming pool, there are many variables that will have an effect. In simple terms, factors that will impact the cost of heating a swimming pool include the size of the pool, litres of water in the pool and the amount of heat required per kilowatt-hours (kWh).

For example, in a small 12 foot circular pool housing 8,000 litres of water, 9.3 kWh of heat would be needed, whereas a much larger 20×40 foot pool containing 100,000 litres of water would need 116 kWh of heat.

Pool sizeRequired litres of waterHeat per day (kWh)
12ft (round)8,0009.3
15ft (round)16,00018.6
18ft (round)25,00029.1
12 x 24ft (square)40,00046.5
15 x 30ft (square)64,00074.4
20 x 40ft (square)100,000116

Once you know the size of the pool and the amount of water needed to fill it, you can begin to calculate how much the cost of water could be. However, the cost of pool heating will be different depending on the method of heating being used.

Heat required (kWh)Oil (£)Gas (£)Electric (£)Heat pump (£)

In conclusion, an electric heater would be a suitable option for a pool that is 20 feet long or smaller, but for larger pools such as the type you may find in a gym or leisure centre, it would be better suited to look at a more substantial option. It could also be worth adding a heat pump for quicker heating and the potential effect it has on cutting costs.