Solar heating for swimming pools – the pros and cons

Solar Pool Heating – the pros and cons
Heating a swimming pool using solar energy has always been a good idea, free heat from the sun is always preferable to a large gas or electric bill, but just how good are the solar heating products available?

If you really want the best solar heating there is then you need the vacuum tube type heater. Prices start from about £3,700. But this article is aimed at solar heating for smaller pool so we will not go in to further details here but follow this link for the Thermecro Evacuated Tube Solar Heating System

For the typical domestic  owner of a small to medium size pool who is  on a reasonable budget there are two main options. The rubber matting type and the new solar pods type. The biggest problem that faces these type of solar swimming pool heaters is that they don’t have a thermostat. You cannot say “I want my pool to be 28C, I’ll just set this dial to 28C” and sit back and two days later the pool is at 28C and it stays at 28C all season long. With solar heating you get what the sun gives you. If it decides to shine then you get 28C but if it decides to stay behind the clouds you get 20C or 15C. If it is important to you that the pool water stays at a constant temperature then solar heating alone is not for you. You will need a back up source of heat and that will mean paying for it.

Nature likes equilibrium. If something hot is surrounded by something cold the hot thing will give up its heat until they are both the same temperature.  Given enough time a large mass of water, like your swimming pool, will reach the same temperature as its surroundings.  This is a major problem in the Middle East where pool water can naturally reach 35C. This is too hot and most pools will have a chiller on them to cool them down. No such problems in the UK where left alone a pool may get to 22C, 25C in a long spell of good weather, but typically 18C to 20C is what you would expect. For most people 20C is too cold but 28C is quite pleasant.  8C might not seem very much to have to warm the water by but it if the ambient temperature is lower than 28C, and that is probably 95% of the time in a British summer, then you are constantly having to add heat to the water while nature is constantly trying to take it back.

The problem we have with solar heaters is that when the sun comes out the weather gets warm anyway.  So is the heat gain in the pool down to the solar heater or would it have warmed up anyway? We have carried out experiments on two pools, side by side and in full sun, one with a solar heater and a solar pool cover and one without. We sampled the temperature every hour and we found, not surprisingly, that the temperature fluctuated with day and night. From a daytime high of 23C the pools could drop to 18C at night but then back to 23C the following day. What we did find was that the pool with the solar heater and solar cover was always warmer than the other pool, usually by about 3C but more in sunny weather. In sunny weather the solar heated pool reached 29C in the middle of the day whilst the non-heated pool was 24C.

During the experiment the weather did turn cool and we had rain. At these times the pools fell back to 18C to 22C but in those conditions no one wanted to use the pool anyway. When the sun came back the temperature of the water rose to 26C and that coincided with a desire to swim.

solar heat graph

Comparison of heated and non heated pools


So we think that, provided you accept the limitations in this climate, solar heating it is worth investing in. We would sum up the pros and cons as follows


The pool temperature will never be constant
The water will cool considerably at night and in a cloudy spell of weather


The heat you do get is free
Most people don’t want to swim in cloudy weather anyway, by the time the weather improves the water has warmed up again.

solar pool heating

Solar Matting on a roof Solar Pod

Putting a liner in a concrete pool

We are often asked about converting a concrete swimming pool to a liner pool, this article will discuss what is involved in making such a change.

It is not unusual for older, concrete built swimming pools to crack and develop leaks. Often the cost of repairing the leaks is so high that owners consider lining the pool with a vinyl liner to seal the leaks. Concrete pools are often painted with water proof paint and this is a job that needs renewing every 3 to 5 years and the desire to do away with the job of painting is another reason why owners consider converting to a liner.

It is not impossible to convert a concrete pool to a liner pool but is does involve a fair bit of work and it is not easy to get a perfect job. The first thing to know is that the pool shell fittings will all have to be replaced. That is the main drain on the floor, the skimmers and the inlets. This is because in a liner pool the shell fittings have a removable face plate with a pair of gaskets behind them to seal the liner around the fitting. You could compare this to wall-papering up to a light fitting. You take the face plate off, cut the paper around the fitting and cover the cutting with the face plate to make it look tidy. It is the same with a pool liner only it has to be water tight. So you will have to get out a pnumatic drill or hammer and chisel and break out those shell fittings back to the pipe behind them, cut the pipe and install new, liner compatible fittings. Then you will have to make good the holes you made getting the old ones out. In the case of the skimmer you will probably have to take the coping stones up and relay them.
The cost of the new shell fittings is not that high in the big scheme of things, about £100 for a skimmer, £10 for an inlet and £30 for a main drain. The main cost here is the labour if you dont do it yourself. It would take a day or two for one person to change these fittings and make good.

The next thing you will need to do is install a “liner lock” to the top of the pool. The liner has a beading welded on to it and that beading clips in to the liner lock at the top of the pool. Liner lock is about £1 per foot and needs to be firmly fixed with masonary screws.  The liner will cover over nearly all of the liner lock and you will not notice it afterwards. If your pool has square corners you should round them off to a six inch radius either with sand and cement screed or a purpose made corner insert. These are about £100.00.

It is a good idea to puncture the floor of the pool to make it non-water tight. Liners can leak from almost anywhere and if the water gets behind the liner it it better that it soaks away in to the ground rather than build up between the liner and a water tight shell forming a bubble.
If the concrete pool has steps then your problems are greater. Whilst it is theoretically possible to make a vinyl liner with steps in it our advice is don’t do it. You will never get a good fit, the liner will not sit back neatly to the back of the treads and there will not be enough weight of water to hold the material on the top step down. If you have concrete steps you have two main options. One is to take them out and replace them with a fibreglass step unit. They are designed with a face plate to seal a liner to. They are not cheap though. The step unit will probably cost more than the liner. A typical 4ft radius semi-circular step unit is about £1,600. That is just for the steps, of course. You still have the labour cost to break out the old ones and install the new ones. The other option is to break out the steps and make good the wall to have a simple rectangular pool and use a ladder to get in and out. A ladder is about £200.00. You could seal off the steps and put a fibreglass corner step unit in, these cost a little less at about £1,400.

So having converted your shell to accept a liner you now have to buy a liner and have it installed. This is where PoolStore come in. You can see our prices by putting your pool dimesions in to our cost calculator by following this link. You can peruse our choices of colours by clicking this link. We offer a nationwide liner installation service. When you are ready to buy your new liner we are here to help.

A Guide to Swimming Pool Coping Stones

Just about every in-ground swimming pool has coping stones around the edge. Over the years they deteriorate and need replacing. This article will tell you what your options are for replacing them.
Until recently all Swimming pool coping stones were sourced from UK manufacturers but now a nice range of Mediterranean style copings are available in the UK. The traditional UK made coping stone comes  in 2 foot lengths and are either 9 inches or 12 inches wide. There are two stlyes and two colours available. The two stlyes are called “bullnose” and “flat top”. Bullnose have a built in backward slope and flat top do not. The colour choices are White or Buff. The most popular choice by far is White Bulnose.

Flat top coping stone

Bullnose Coping Stone with backward slope

White swimming pool coping stone

Traditional White Bullnose Pool Coping

As well as the standard straight coping you can also get what are known as “specials”. These are the corner stones for internal or external corners and “radius” copings for going around roman ends (as shown in the image above).
The traditional copings always stand out from the paving surround and many people like the way they define the edge of the pool but others prefer the copings to match the surrounding paving. This matching style is typically Mediterranean and now there is available in the UK a Spanish pool coping that is not only great looking as a stand alone coping but comes with matching paving slabs if you want them.
The Sahara coping has the built in back slope while the Ardoise coping is a flat top. Ardoise has a riven finish while the Sahara is smooth.

Ardoise Coping Stone – Flat topped with riven finish and 330mm wide

Sahara Coping – back sloping, smooth and 270mm or 330mm wide

Surprisingly these Mediterranean swimming pool coping stones are not more expensive than their UK counterparts.  Below are the prices for a 12ft x 24ft rectangular pool for comparison.

Traditional 9 inch £820 .00
Traditional 12 inch £1,000.00
Sahara 270mm £760.00
Sahara 330mm £820.00
Ardoise 330mm £1,010.00

For more information on the coping stones and matching paving slabs featured here follow the links below
Click here for Traditional Swimming Pool Coping Stones
Click here for the Sahara Range of Swimming Pool Coping Stones
Click here for the Ardoise Range of Swimming Pool Coping Stones

You have got an above ground pool and now you want to heat it

So, you have bought an above ground pool, probably an Intex type pool, that sits on your lawn. You have filled it with water, connected up the filter pump and you and your family are all ready to climb that ladder and step in. But then you hear “it’s freezing cold! I am not going in that!”.
Sound familiar? You need a heater. In this article we will discuss the various options for heating a garden above ground pool. We are talking about the type of pool like the one pictured below, you can buy them from us or from Argos, Toys r us, B&Q that sort of thing. Typically 8ft to 18ft round with a combined paper filter and pump.

If  your pool is in the 8ft to 12ft bracket then brace yourself: The heater is going to cost more than the pool. Infact regardless of how big your pool is, if you want a really good, efficient heater it is going to cost way more than the pool. We will not be discussing solar heating systems in this article, we’ll talk about that in another article.

So let’s start from first principles. If you get a cold drink and a hot cup of tea and leave them both on the table for an hour what happens? The cold drink gets warm and the hot drink gets cold. The liquid warms up or cools down to the ambient temperature surrounding it. It is exactly the same with your pool. The only difference is your pool sits there day and night  so whilst it may warm up some in the day it will cool down at night. So if you do nothing the water will reach the average day/night temperature for the time of year. In a typical british summer that is about 17C (63F), not especially warm.

The first thing you should do it buy a solar cover. Even the cheapest type will help but a good quality 400 micron solar cover will help the sunshine to warm water and also help keep the heat in during the colder nights. Using a solar cover should add at least 2C maybe up to 6C to the temperature. That will bring it up to about 19 to 23C (66 to 73C). 23C is not bad, on a really warm day most people would swim in 23C.

If the solar cover does not warm it enough for you then the next stage involves forking out for heater of some sort. There is a big barrier that affects your choice and that is the fact that from a 13amp plug socket in the wall you can only run a 3kw appliance.  3kw heaters are a very popular choice for that reason – you do not need an electrician to wire it in. You plug them in and connect them up and away you go. This is great but unless your pool is 10ft round or smaller you will not get the pool very warm. A 3kw heater will be OK on a 12ft pool but don’t expect anything over 25 or 26C in normal summers. Intex make a cheap 2kw heater. At £95.00 it is good value but it is not hi-tech, it has no thermostat but it will warm up a small pool. Elecro’s 3kw Nano heater at £215.00 is a much better piece of kit.

If 3kw is not enough to heat your pool, i.e. your pool is bigger than 12ft round then you have two main choices. If you are happy to get an electrician in then get a 6kw or a 9kw direct electric heater. Elecro are by far the best manufacturer of these heaters. 9kw will heat a pool up to 18ft round. Bear in mind that when running a 9kw heater and assuming day rate electricity of 13p per unit it will cost £1.17 per hour to run. They typically need to run for 4 to 6 hours per day to maintain the temperature. In a 150 day season your lecky bill could be over £1,000.00. Every season. You will not save electricity by having a smaller heater, it will cost the same and just take longer to heat the pool.

Don’t fancy the idea of paying £5,000 in electricity over the next 5 years? Then a heat pump is what you need. An Ecowarm EW10 gives up to 9.5kw of heat, but it only draws 1.9kw in electricity. It can plug in to the wall socket, no need for an electrician. At 25p per hour to run your lecky bill for the season should be more like £250.00.  So what is the drawback? Well, the EW10 costs £1,200.00 to buy but with a saving of £750 per season it pays back after 1 year.
“£1,200 for a heater, the pool only cost £300!” I hear you say. Yes, that is quite right. Heating up a large volume of water is not a cheap and easy thing to do.

Further Reading: How much does it cost to heat a swimming pool?

Click the links below to see the products discussed in this article:

Intex 2kw heater

Ecowarm Heat Pumps

Circular Solar Covers

Elecro Nano 3kw Heater


New Stain Removal System for Swimming Pools


PoolStore is pleased to introduce a new system for the removal of stains from the walls and floors of swimming pools.


Stains in swimming pools are almost always caused by metals in the source water. The metals come out of solution in one or more place on the shell of the pool and can seem to be impossible to remove by conventional cleaning. The stains are usually brown in colour but can be yellowy or black.  Fibreglass pools seem to be more prone to staining than any other type of pool.


The removal of stains is a 2 step process.  First you have to get the stain off the wall by getting the metals out of there and in to the water. Then you have to get the metals out of the water.


Start by adding  Multi Stain Remover to the water. This is quite a strong acid and will take the metals out of the walls and in to the water.


The second stage is to remove the metals from the water using No More Metal. The metals are held in suspension so they can be filtered out. No More Metal should be added on a regular basis thereafter to keep the level of metals down in the pool water and so prevent the stains from re-forming.


Stain removal is not a simple process so read the instructions carefully.  One thing to note is that the first product is very acidic and will alter the pH balance of the pool. When re-balancing the water you must do it gradually over a few days or you will un-do the work that the stain remover did and the stains will re-form.


metal stain removerPool Stain Remover