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Swimming pool boiler or heater – Gas boilers for swimming pools

swimming pool boiler; gas swimming pool heater; pool heaters; warm water; heater; swim;

A swimming pool boiler, is very much like a domestic boiler in that they generate heat by burning gas inside a combustion chamber within the energy-efficient boiler; this heat is then transferred to swimming pool water, via a heat exchanger, which is subsequently pumped back into the swimming pool, resulting in a comfortable temperature for swimming etc.

Some people often refer to swimming pool boilers as swimming pool heaters – they are in essence the exactly the same thing. They warm water to your desired temperature, resulting in you having a comfortable pool water temperature in your swimming pool.

In the United Kingdom, gas boiler systems are the most used method of swimming pool heating. They regularly outsell heat pumps due to the speed in which they can warm a pool , to ensure you can swim whenever you want and the fact that they are not dependent on air temperature, allowing them to be utilised all year round, unlike a heat pump heating system.

Our highly efficient swimming pool gas boilers have lower running cost than electric pool heaters. Our gas boiler range for  swimming pool heating is one of few in the UK’s only condensing pool heaters, to be powered by either propane gas ( LPG) or natural gas (mains gas).They are also more cost effective to purchase than electric pool heaters or heat pumps.

A gas swimming pool boiler is highly energy efficient these days, as condensing boiler technology ensures the maximum heat transfers from the gas boilers exhaust gases into the heated water. Our swimming pool heaters / swimming pool boiler range is up to 105% efficient as these gas boilers recover the latent heat from the flue gases , via a stainless steel heat exchanger as they heat pools.

With our condensing gas boilers, heating your swimming pool, you can rest assured that your getting an energy efficient pool boiler, resulting in lower cost to heat your pools or hot tub /hot tubs or spas ,domestic or commercial ,especially when compared to electric pool heaters as an electric heater can be very expensive to heat your pool.

An air source heat pump relies on a high external air temperature to operate efficiently and will have to go into a defrost cycle if the air temperature is too low using electric heaters to defrost, their efficiency drops considerably with a lower external air temperature too.

These swimming pool gas boilers can also be used as a backup solution or conjunction with solar heaters or solar panels, to top up the water temperature on cloudy weather days, as solar panels or solar heaters as an energy source aren’t as effective in these conditions.

Swimming pool heaters gas fired

Gas condensing swimming pool heaters utilise the latest cutting-edge technology to deliver effective and quick pool heating. Our gas pool heater range, with an energy efficiency rating of up to 105 percent, may save up to 32 percent on operating fuel costs when compared to an older direct fired gas swimming pool gas boiler.

Our swimming pool gas heaters / pool boilers can be fired by either natural gas or LPG gas (propane gas).So whichever gas you decided to power your gas boiler, we have you covered.

swimming pool heater gas fired from Flexiheat UK:water heater:natural gas:propane gas:stainless steel heat exchanger

Swimming pool heating from Flexiheat UK for in ground swimming pools

So you also wish to change your gas over to from LPG to natural or vice versa , this is easily done with a simple gas conversion kit to suit, which is an easy installation to do by any plumbing company that holds the relevant certificates for working on these gases.

Swimming pool boilers gas fired

Another benefit our our boiler range , is that we can do a combi version , that will not only heat your swimming pool, but also will produce domestic hot water for showering etc. This is another why we have the best boiler range for a swimming pool. As we can warm water, from cold not only for heating the pool, but also for the domestic water required, after you’ve had a swim – which is an extra versatility that many of our competitors on the market can not provide.

Our combination pool boiler, (the boiler services both the pool heating and domestic hot water heating systems requirements) benefits from being compact in size, thus saving space and install time in your pool boiler room. We also do a external combi heater, that not only saves even more space, but also saves on installation of a flue system, as these units have a forward facing flue install configuration, which efficiently and neatly fits onto the pool boiler ( see pictures below )

external gas pool boiler; external gas pool heater

External gas pool boiler or heater in natural gas or propane from Flexiheat UK

Another benefit of an external gas fired fully weatherproofed pool boiler is that you can service or maintain the boiler without having to have access to the property. The same is applicable for any repairs that may be required of the heating systems.

Safety is also another benefit of an external installation of a swimming pool boiler, as there’s no risk of CO2 poisoning as the boiler is situated in the external air environment. Another installation safety feature of an external mounted gas boiler benefits from is if there’s a gas leak, again the gas is dispersing into the free external air.

If you require a new boiler or pool heater, then our best advice if you want a boiler / pool heater to heat your pool along with a requirement for domestic hot water services – then you should consider one of our reliable combination swimming pool boilers.

Because of the speed at which they can heat a pool and the fact that they are not dependent on air temperature, gas pool heaters regularly outsell heat pumps, allowing them to be utilised all year.

Swimming pools boiler/ heater sizing

Variables such as having a solar cover, temperature, and how frequently you use the pool can all have an impact on the effectiveness of your boiler, and need to be accounted for to ensure your never left with cold water when you want to have your daily swim.

The evaporation of water from the surface accounts for the majority of heat loss from a swimming pool surface and a little through swimming pool liners. Thus this following table is based with a swimming pool covers ,which covers swimming pool , to avoid any heat losses caused by wind conditions and evaporation.

This pool boiler / heater size guide is for outdoor swimming pools in the South of UK, from late April until early October ( basically summer swimming) . For northern UK swimming pools, you may need to increase the boiler size by 30% to 50%, depending on the swimming pool’s exposure.

To get the most out of your swimming pool heating system it is highly recommended that you use the 60 Degrees C temperature on the below pool sizing chart, as when the boiler heating water flows out at 60C and return water comes back at 40C, the boiler will always be in the maximum energy efficient condensing state, thus reducing the swimming pool heating systems running costs.

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Swimming pool heat exchanger data for gas fired boilers from Flexiheat UK for pool heating

To be fair you can never over-size one of our gas boilers for a swimming pool , as the are full modulating and will adapt the output to the pool heating requirements, the larger the gas boilers are the quicker they’ll warm the pool water from cold water- its as simple as that .Our top tips or advice as a company is – There is very little cost difference, from one of our 25 kW gas boiler to our 30kW boilers for example – so go for the larger heater or boiler swimming pool / pool boiler/ pool heaters swimming .

Please remember all gas boilers should only be fitted (installation process) by a gas safe registered engineer and should be serviced regularly i.e. serviced annually. Remember gas regulations and gas safety is paramount when it comes to a gas boiler or gas heaters that heat your pool -regular servicing ( annual servicing) is vital.


Gas boiler range

Our reliable and efficient swimming pool gas boiler range for pools – are available in LPG (also referred to as propane), which sometimes leads to customers calling them a propane pool heater or in natural gas (mains gas) versions. Either fuel, can be referred to as a gas swimming pool heater or heaters swimming pool

Our gas pool heaters, are fully modulating, which means they provide a precise and clean burn with a correct air/fuel combination every time they operate, ensuring a boiler is kept in top condition, and running efficiently. When run at 60/40C flow and returns, you’re operating at the best energy efficient temperatures, which means that the boilers are 105% energy efficient, reducing your heating costs.

Of course, you can operate the pool heaters at 80/60C, which will result in a faster heater up time, but will consume more energy as a result. It is your choice as the best option for you to heat your pool depending on your requirements.

We do a 24kW, 28kW,34 kW, 50kW, 60kW, 75kW, 100kW and 115 kW gas fired internal and external swimming pool heater in single boiler units, or we can cascade the swimming pool heaters up to 960 kW, so we can heat your pool whatever the size is.



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Singular Boilers – 24kW to 115kW Output

Where we differ from the older technology pool heating boilers

Some of the older gas boilers on the pool heating market, have the heat exchanger for the pool water internal to the unit. As a company we don’t thing this is best solution.

This doesn’t make sense to us from an engineering point of view

As it means that you have to dissemble the boiler, just to be able to clean out the pool heat exchanger. This is not only very time consuming and labour intensive, but also, you’re on potentially “sticky ground” as your dissembling a gas appliance, and really you should be suitably qualified (such as gas safe registered). This is gas your dealing with, and it can be lethal if you don’t know what you’re doing.

The Solution ? which is best for service and repair

Easy, just separate the gas boiler , and the heat exchanger for the pool water – You have the same system or services as the older technology – just in two separate components –

There will be fewer problems because the pool water does not enter the energy-efficient boiler. The pool heating is done via dedicated specialist heat exchanger – which can be corrosion resistant titanium or similar construction.

What’s the benefits?

There are many –

Mounting options –

You can mount the heat exchanger in either a horizontal or vertical orientation, to suit you site requirements from your swimming pool pumps

Swimming pool heat exchanger mounting options Flexiheat UK

System diagram showing pool pump and swimming pool filters for the pool heaters


Service / Maintenance

Service / maintenance of the pools heat exchanger – it’s incredibly easy on the day  – just remove the end caps, and then you can pull out the elements for inspection / cleaning.

Swimming pool heat exchanger instal picture for use with gas swimming pool heating Flexiheat UK;heat pump;british thermal units

Heat exchanger for pool heating coupled up to a gas fired heater / boiler

Boiler repair, plumbing or gas safety checks is also easier when the two heaters are separated, unlike the Certikin genie heaters and other brands on the market. Gas safety services checks should be done annually.

swimming pool boiler exchanger for heated water

Easy to access and clean heat exchanger – no disassembling of the boiler (you need to be gas safe registered engineer to do this- as per the gas regulations) – thus regular servicing is easy and uncomplicated.

Oil Fired pool heaters

Domestic fuel oil is burnt in a specialised swimming pool oil heater, again they working in the same way as a domestic boiler, in that they have a combustion chamber, where the oil is burnt, and that heat transfers into the pools water , normally via a central exchanger of either stainless or titanium. Oil heaters are initially expensive to buy, install and also to service, (if you can find an engineer first) – when compared to gas boilers

They also have some other disadvantages

  • Oil is a fossil fuel, with higher carbon emissions than gas – so you’re contributing to a larger impact on the environment if you use oil as the heating system fuel
  • Fuel cost to heat your pools – Oil boilers have a relatively high running costs – only second to electricity for heating pools, a gas unit is the recommend  and most convenient and cheapest at present. Your daily swim will cost less with a gas heated swimming pool heater.


Services and Brands 

We provide an excellent service as you would expect from any professional company, so should you require any advice or more information on our reliable gas fired swimming pool heaters or swimming pool gas boilers to suit any size swimming pool from domestic to commercial, that will give you many years of effective trouble free operation, then give our friendly sales team a call on 01202 822221 or use our contact form above on the website.