How to solar heat a pop up pool for very little cost
Picture the scene – it’s a sunny day and the children want to splash about in your cheap and cheerful pop up pool. You rush out and buy that $100 12ft round pool and fill it with 7000 litres (2000 gallons) of water. The children step in and immediately shriek that it’s freezing, and pretty soon, they’re out. To console them, you hook up the garden hose to your hot water tap and try to increase the pool temperature. Unfortunately, you need a lot of hot water to increase the pool temperature, probably your entire hot water supply that you would use in a normal day for washing and showering.
The alternative which is what I would like to show you is a pool that easily reaches temperatures of 28 to 30 degrees Celsius (82 to 86 degrees Fahrenheit) with a few hours of sun a day. With readily available materials from the likes of Amazon, I’ll show you what you need to keep the costs down and the family and friends happy. Like you, I started out knowing nothing about pools. Yes, all the information is out there on the internet, but it requires a lot of trawling. If you google entries such as ‘how to heat my pool’ you will get countless entries for sophisticated large pool operations with permanent installations from places like Florida.
What I present here is a temporary pop up pool with a quantity of water around 7000 litres (2000 gallons). In addition to this, I show you how to add a solar heater to warm the water and how often you need to operate it. Sure, there are countless pools out there so by and large what I present here will serve you well for larger pools. I also provide you a link as to how to size the pump and what you need to keep the pool clean.
The basic assumption here is that you would like to add a temporary pool to your garden. By temporary, I mean for the duration of the summer months (June to August in the Northern hemisphere), and then remove it for winter storage. The water stays in the pool for the duration of the summer and no further water is added. The other important factor to bear in mind is a location to install the solar heater. Ideally this should be placed as close as possible to the pool.
It is obvious that water weighs a lot, so if the pool says 6000 litres, that is 6 metric tons of weight distributed over a relatively small surface area of the garden. It goes without saying that you should place the pool on firm ground. Placing a pool on for example decking carries the risk of collapsing. The ground needs to be really level.
To check if the ground is level, get a long piece of wood (3m or 10ft) and check it for trueness by laying it on your living room floor. If the piece of wood does not lie flat on the floor discard it and get another. With the knowledge that the wood is true, you can place your spirit level on the wood. Now, outside in the garden you can lay the wood on the ground and check with the spirit level if you indeed have a flat location, or if you need to level it. A centimetre or two might not seem much, but when the pool is full you will really notice it if the water slops over one side.
Next, place sheeting over the area where you intend to place the pool. I recommend making this larger than the space taken up by the pool by about 30 cm or 12 inches. The reason for this is that inevitably water splashes over the side and the ground quickly becomes muddy. With a margin to play with, you stop the mud getting into the pool.
For the worked example here, I will be showing you what you need for a pool that is small enough for most gardens and that will not cost the earth. You can of course size bigger or smaller taking into account the essential points covered below, and in more detail in my e-book.
There are many temporary pools available which cost little money. The example we are using here is an Intex Easy Set Pool (Amazon UK) which is a circular pool with an inflatable top ring. Once the ring is inflated, which takes about 10 minutes at most, the water will raise it up as it fills the pool. My recommendation is to start with a pool that costs very little and see how you get on. You can always progress to steel frame pools later on, say for next season.
The amount of water contained in the pool is a big factor in the heating calculations as well as the sizing of the pump. A basic rule of thumb circulating on the internet is that you need about the same surface area of solar collectors as you have surface area of water. I have found that this is not strictly true and you can get away with less collector area; clearly it does depend on how much sun you get as well as countless other factors.
Nevertheless, the children are usually the determining factor here, so I have assumed a pool large enough to accommodate 3-4 children in the age bracket 6 to 10 all playing in the pool, and some room for Dad or Mum too. The depth is about 90cm or 35 inches which is deep enough to do some underwater swimming and search-and-retrieve games and a diameter of almost 4m or 13 feet. Could we go bigger? Yes we can – but let’s start with this size and work upwards.
Heating water with electricity is very, very expensive. Much better is to pump the water into lots of black tubes that wind backwards and forwards and eventually return to the pool. The black tubes absorb the suns rays and heat the water. If you have ever experienced turning on a garden hose that was left in the sun you will know just how hot this water can become. And here is the first critically important point: a pool will heat much faster if you continuously flow water through the solar collector whilst it gains a few degrees in heat than allowing it to sit and heat up to extreme temperatures. In fact, if a solar collector is hot to the touch it is not working properly. This means that the water inside is not absorbing the heat. I’ll explain more with a bit of simple maths later.
The tendency here is to think that bigger is better. It is not. You have to correctly size the pool pump to the amount of water you have in the pool and critically to the height to which you will pump the water. Basically you want a pump that can turnover the entire quantity of water in about two hours and be able to have enough wattage to get the pump to a certain height to reach the collectors. The latter point is crucially important if you intend to mount the solar collectors up high, for example on a roof. In the worked example I show in my ebook, I will show you what ‘up high’ means. In a nutshell, the pump has a maximum height it can pump water to as well as a nominal height. The former means it will pump it up to a height and not flow any more whereas a nominal height means to a maximum height with a reasonable flow. It is this we are after.
This is where I recommend you do not use the
stock filter units that come with these pop up pools. The stock filter unit has
a paper cartridge and you will be having to clean it out regularly. I recommend a sandfilter. The pump moves the water through a unit
containing sand (or other material such as glass granules). The sand removes
the suspended matter in the water. With
a sandfilter applied to a pop up pool you will hardly have to do any
maintenance all season. More often than
not a sandfilter comes with the pool pump.
When you select a sandfilter which comes with a pump the deciding factor
is the pump. You do not have to buy
these together.
This is where I recommend you invest most of your money. It is crucially important to ensure that the water is maintained at the correct pH levels (7.2 to 7.6). Failure to do this will lead to discolouration of the water, and eventually it will turn green. Fortunately, there is a very easy way to keep the pool clean and that is with a saltwater unit. When you have filled the pool up for the first time, you dissolve about 25kg or 55 lbs of regular salt in the water. The pump ensures water flows through the sandfilter and then through the saltwater unit. What the saltwater unit does is to electrolyse the water and produce chlorine. The chlorine as we all know kills the bacteria and keeps your pool nice. The major benefit is you no longer have to add any other chemicals during the entire season – and the children will never complain of sore eyes either.
All the parts we have discussed here need to be connected together with 32mm or 1.25 inch piping. There are smaller and bigger diameter pipes available, but to avoid having to step up or step down to join the various elements together, stick to 32mm/1.25inch throughout. What is essential here is that the stock connectors for attaching the pipes to various elements are often of inferior quality. From the start buy a bag of quality jubilee clips and white plumbers tape. This will avoid leaks.
It is worth explaining how all these parts fit together and why we need all of them. The pool water needs to be cleaned of suspended matter and the water must be treated to keep bacterial growth in check. This is why we need a filtration unit (the sand filter) and the chemical treatment (the saltwater unit). The solar collector warms the water and the entire circulation is carried out by an electrical pump. Regardless of whether it is a sunny day or not, the pump must run for a couple of hours a day to ensure the water remains clean and bacteria levels at the right level.
| Item | Example Product | Comments | Cost in UK Pounds |
| Pool | Intex Easy Set Pool 366cm x 91cm (AMZ UK) — | 5-7000 litres | 100 |
| Sand filter with Pump (sized at 4m3/hour) and Height Nominal equal to the height of the top of your solar collector | Bestway Flowclear Sand Pool Filter 1000gal/hr; or intex Krystal Clear Sand Filter and Pump 1,050gal/hr | Key metric: litres per hour, and H Nominal of the pump | 125 |
| Saltwater Chlorinator | Bestway Hydro-Force Chlorinator (AMZ DE) | It’s expensive but worth the investment. | 160 |
| Pool hose | Jilong pool hose 32mm, 5m | Assuming your collector is located 4m high, you need two lots of 5m (with a bit of spare) | 50 |
| Solar collector | Speed Solar Sun 49123 Solar Collector Low-Density Polyethylene for 0.7 x 6 m | You need just one of these; they do need to be supported if not lying flat on the ground. | 130 |
| Sand | 25kg of good quality builders sand from a DIY store. Check quantity required on sand filter | You can go upmarket and get glass media | 5 |
| Salt | DIY Store – 25 kg bag | Any good quality salt | 5 |
| TOTAL | 570 |
There are several additional items which if you can spare the extra cash could be very helpful. A pool cover will prevent dirt such as leaves getting into the pool. A solar pool cover will do a good job of keeping the heat in at night and a ground cloth is very helpful to limit mud if the pool is placed on a lawn. Although you can easily vault over the side of the pool, smaller children may struggle to get in and out of the pool. Exceptional care is needed with ladders: they are needed in the pool for small children to be able to get out. But they must not be left in when the pool is not in use. Actually, using a pool cover will always remind you to remove the ladder. You may find a bypass set is helpful to direct the water away from the solar collectors when you do not want to use them.
The diagram shows the various components of the system. As you can see, the water exits the pool from the pipe located nearest to the bottom of the pool. From here it flows via a short pipe to the pump. The pump pushes the water to the sand filter. The sand filter removes the suspended matter and the water continues to the top of the solar collector. The water exits the solar collector at the bottom most point and finally arrives at the chlorinator. The chlorinator electrochemically reacts with the small quantity of salt in the water to produce chlorine which treats the bacteria in the pool. The water arrives back in the pool through the topmost connection.
The positioning of each element is best practice; you really want to avoid any suspended matter entering the fine tubes of the solar collector. Similarly, it is best that the chlorinator is last so that its impact is felt immediately in the pool. The addition of a bypass (shown as ‘divert’ in the diagram) may appear to complicate things. But it is helpful to have the option to divert the water away from the solar collector. If you leave your house for a while, it is probably sensible not to have water being pumped up to your roof if you can avoid it. Whilst the fittings are good, they could spring a leak and you would be none the wiser. Better if it is circulating in the garden whilst you are away. Furthermore, if you run the pump at night and the water temperature is higher than the ambient air temperature, the solar collector will work in reverse: it will cool the water in the pool. Despite all this, if you are on a tight budget, the bypass can be ignored or invested in at a later date.
There is an awful lot of information about pool pumps on the internet. But the pump is the most important part to get right. Too big and you blow the tops off the collectors, and to small and you have inefficient heat transfer. My Kindle e-book explains this part very clearly, how exactly to size the pump for your needs.
The solar collector consists of black tubing. The black colour absorbs the sunlight and warms the water in the tubing. If you leave the water stationary it will reach high temperatures in excess of 50 degrees or more. However, it is much more efficient to move the water constantly through the tubing achieving outlet temperature increases of a few degrees, than leaving a small quantity to reach a very high temperature. If you are interested, you can work this out in detail by reading my Kindle e-book.
The chlorinator reacts with the dissolved salt in the water to produce chlorine. No further chemicals of any kind are needed, the entire season. For the process to work properly you need to have dissolved a large bag of salt in the pool. You should read the manufacturers specification here, but typically for the 7000 litre pool we are using, 25 kg of salt is more than enough.
In my experience, I can move the pool temperature about 1 degree an hour using the equipment listed above and about 4 hours of direct sunlight.
My garden is shady with a tree that casts a shadow all morning on the solar collectors. This isn’t a problem: I run the pool from midday until about 4pm, and the temperature increases from 20 to 24 degrees.
I apply the solar pool cover to keep the heat in overnight. The next day I notice that the pool temperature has dropped by about 1 degree to say 23 degrees. I run the process again the next day and it increases to 28 degrees.
I have found that it tops out at about 30 degrees.
This is more than warm enough and the children love it!
For more information
To see more information including photos of actual installation, please visit the Amazon kindle store for my e-book. If I can help further, do not hesitate to write me at Oli@Adoli.com
Disclaimer
Please remember that all pools are dangerous for children. Adult supervision is required at all times. Do not leave your pool unattended. If going away, ensure no ladder remains in the pool, and ensure there is a sturdy fence around the pool to prevent minors entering pool. Remember that electrical devices near water represent an acute risk of electrocution, as does working from heights. If in any doubt, check with a professional in your neighbourhood. Before you start up your pool pump or connect any devices, I recommend to have the installation thoroughly inspected by a professional pool technician.
I do not warrant that the installation as described here is safe and works perfectly in all cases.
