DIY Solar Pool Heating Part 1

Who doesn’t love a refreshing swim? I certainly do. And although i enjoy a swim in an unheated pool in the middle of summer, the rest of the year its a little too cold to enjoy. And then there is night time swimming. Swimming in a cold pool in the evening, although refreshing, is not something i did very often due to the temperature being just a little too.. well.. cold.

So i thought, let me try and heat the pool DIY style. So i did some googling and came up a plan for a little proof of concept. This article will cover this proof on concept, and what effect it had on the teperature of the pool.

First, i bought a solar pool blanket, which as far as i am converned is crutial for a heated pool. It prevents heat loss, and prevents drastic overnight drops in temperature.

The pool cover was purchased from poolcover.co.za for approximately R900 including postage, and i am very happy with the quality of the cover. My pool is small, so removing the cover and putting it back on is simple. My pools dimensions are 3m x 2m, with a depth of approximately 1.7m

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I let the pool cover do it thing for about a month before installing any solar pool heating. Besides keeping the pool a little warmer, some of the other benefits of the cover include:

  • There is pretty much no evaporation, so the pool pretty much stays at the same level. This is already a huge bonus and i rarely have to top up my pool which saves water.
  • The pool stays a lot cleaner! I don’t have a creepy crawly type device, and before i used to use a manual vacuum hose about twice a month. I now only have to do so about once every 2 months. The cover does however sometimes need a rinse to clean the dust of of it.

After a few days, the temperature of the pool definitely increased by about 4 degrees. This was already a big improvement, and may be enough of an increase for most people. But i wanted to see how far i could push this. So i went ahead and started building a DIY Solar heating system. The components are as follows:

  • 100 metres of 15mm low pressure black HDPE water pipe.
  • A few metres of 40mm High pressure pipe. Low pressure pipe can also be used i just couldnt find any.
  • Some pipe connectors to join all the pipes
  • A couple of ball valves to control the water flow up onto the roof.
  • Some left over metal bars to support the coiled pipes
  • Some cable ties to hold the pipes in place

The price of the piping and connectors etc was approximately R900.

Next was adding the 40mm piping onto the existing pool plumping system, and running the pipes up onto the roof. It looked like this:

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Next was hooking up the solar piping system. Once installed it looked like so:

IMG_0532

In a nutshell, this all gets connected to the normal pool piping system as mentioned above. So just after the pump and filter and before the water gets pumped back into the pool, some of the water is diverted up onto the roof. The water gets circulated through the black piping and gets heated by the sun before being returned to the pool. What i have also done is adjust the timing of the pump, to turn on and off every 30 minutes for about 4/5 hours during the hottest part of the day. This allows the water in the pipes to get really hot while the pump is off, and this really hot water then pumps the hot water into the pool when the pump comes on.

A picture of the piping connected to the pool piping system:

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There are effectively 3 ball valves. This allows you to turn on/off the solar heating when required for maintenance etc, and also it allows you to control the amount of water going up onto the roof, and therefore the temperature.

This system is effectively just a prototype, so there are a lot of improvements that can be made. Some limitations of this system:

  • The piping should be on a flat matt black surface to really absorb all the heat from the sun. Matt black is apparently best for solar absorption.
  • Because the pipes on this system are placed on top of a corrugated roof, it will not absorb as much heat as on a flat surface, and will be adversely affected by a bit of a wind.
  • 2 Coils is not that much, 4 coils would obviously be more effective.

Version 2 of this system will address these issues. However this system has been surprisingly effective given the limitations. On a really hot week in January, the pool temperature went up to 28 degrees on some days, which was absolutely amazing, especially for night swimming. That week was particularly hot, but generally the pool temperature has averaged around 23/24 degrees, which is still a lovely swimming temperature, although not quite as amazing as that 28 degrees!

The same time last year, without any pool cover or solar heating, the maximum pool temperature was approximately 17/18 degrees, so i already managed to increase the temperature by 10 degrees which is pretty awesome.

For more details and for detailed pool temperature analysis, you can look here. This page is part of my custom built home monitoring system.

So… off to plan Version 2. Version 2 will consist of the following:

  • 4 black piping coils
  • Coils will be placed inside matt black painted container with a flat bottom surface to maximize solar absorption
  • Moving the coils to a better location which will be north facing to better collect solar energy.
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