Learn how to make a DIY solar pool heater using inexpensive material from the hardware store on a weekend. This complete step-by-step tutorial and video are perfect for beginners.
We were really excited about the pool in our backyard when we bought the house.
We soon realized that we could only use it for about 3 to 3-1/2 months of the year because there was no heating. There is a gas line going to the pool but at some point there must have been a leak and it has been tagged.
It was especially frustrating in spring and fall when the daytime temperatures were 90-100F but the water temperature was around 65F! This is one of the biggest issues with in-ground pools.
So we decided to look into options for heating the pool.
After looking at all the solar pool heaters available, we decided to make our own because –
- We can make it for much cheaper
- we can make it sturdier than the other budget options.
- It really is quite simple and easy to make!
Our goal for the solar pool heater –
- We want to be able to increase the number of weeks/months we can use the pool.
- We are NOT trying to heat the pool to be able to use it in the middle of winter.
- We want to be able to store the pool heater away easily when not needed – like in the winter or middle of summer.
We researched many designs and tried a few and came up with a system that works.
First, let’s talk about the basic concept.
Homemade Solar DIY Pool Heater
Below is the basic schematic showing a solar pool heater at work.
The concept is quite simple really –
- The pump pulls the cold water up from the pool.
- Water goes through a valve to regulate the flow.
- Water circulates through black hoses and absorbs heat from the sun.
- Hot water goes back in the pool.
There are two extremely key components of the solar heater
The hose – The black hose is where everything happens – absorbs the heat from the sun and heats up the water. We need this to be as long as possible and the best way to do that is to coil it up!
The valve – Water needs time to heat up in the hose as it flows through. The flow rate makes a huge difference and to be able to control the flow, a valve is placed at the inlet of the hose.
How to make the DIY solar water heater –
Here is a video showing you how we went about making our solar pool heater. Step by step instructions along with tips and tricks follow below.
Step 1 – Build the base
The purpose of the base is to support the hose and can be built in many ways.
We tried two ways to do this –
- Using 2×4 joined in an X with half-lap joints
- Using 2x4s to make a simple grid.
We found that the grid built using 2x4s, although used more lumber, was the best because it had more support for the hose.
Step 2 – Make the hose coil
Leaving about 2ft of hose free, wrap the hose onto the grid and use strap clamps to clamp it down.
We found that these with one hole worked best and also saved on the screws.
This is probably the longest part of the project. The hose gets tangled and is a little hard to wrap so it is best to do it in an open space.
There was really no pattern on how we added the clamps. We just added as and when we felt like the hose needed support to stay in place.
You can also use uv-resistant zip-ties if you like but the clamps worked really well for us.
We decided to make 2 of these coils and will probably make at least one more. The more coils, the faster you can get hot water. We will discuss this in more detail later.
Step 3 – Paint black
Paint the hose and the clamps with a matte black spray paint.
Although this step is optional, I highly recommend it. The key is to minimize all reflections from the surface of the coil – from the clamp or the hose.
Step 4 – Make reflectors (Optional)
We also made a few reflectors by stapling aluminum sheets to 1/4″ plywood. This can be adjusted to concentrate more sunlight onto the coils.
Step 5 – Connect
- If you have multiple coils, connect them in tandem.
- Connect a valve to the main input of the coil.
- A hose from the submersible pump is connected to the other end of the valve.
- Connect an output hose to the output of the final coil and into the pool.
Step 6 – Let it run
Once the pump is on, water will flow through the coils, warm up and go into the pool.
The valve needs to be adjusted so you can control the amount of water going through the coils so the water gets time to warm up.
Alternatively – Instead of the pump, you can directly connect the incoming hose to a water outlet if you are trying to fill up a pool.
So that is the solar pool heater!
How warm can a solar pool heater get?
When we started exploring solar pool heaters, I was skeptical about how well it would be able to heat up the pool.
With ONE coil –
After we made the first coil, on a 80F day, we let it run for about an hour and we tested it.
- Pool water temperature – 70F
- Solar heated water temperature – 90F
WITH TWO coils –
Then we added another coil and on a day with similar temperatures, here is what we found –
- Pool water temperature – 70F
- Solar heated water temperature – 110F (!!)
So, you can see that a solar pool heater can get pretty warm! It was able to raise the temperature of the water by 20-40F depending on the length of the hose.
How long does it take solar to heat pool?
The answer to this depends on the size of your pool obviously.
Here is how it worked for us –
Our pool is 20K Gallons. We ran the two coils in tandem for about 3 days during peak sunlight time (around 10 am – 5 pm).
The temperatures during the day went up to about 84F. At the end of the third day, the overall water temperature was about 78F – good enough to swim in!
The time it takes the pool to heat up also depends on the flow rate of the water going through the coil (controlled by the valve).
The faster the flow, the less time water has to heat up in the coil.
To show up exactly what that means, we conducted an experiment throughout the day (we are engineers and scientists here after all).
Below is a chart of how the water temperature changes depending on the flow rate for one and two coils.
Here is what the chart tells us –
- Two coils get you a higher temperature increase for the same flow of water
- As you increase the flow rate, the temperature increase is lower.
Do solar pool heaters work?
Obviously, the temperature increase was a combination of direct heating of water from the sun as well as the solar pool heater.
But we completely believe the solar pool heater had a major effect in being able to get the pool water temperature up to a swimmable level in the end of April.
For comparison, last year, we had similar temperatures and we were only able to start using the pool in early June.
Does solar pool heating work in winter
Does it work? Yes, it will work as long as you have bright hot sun.
Will it be good enough to help heat up the water in a pool of our size to be swimmable – most probably not – at least not with the way we designed them.
The main reason we designed them this way, apart from the fact that it was simple and easy to do, if so that we can easily put the coils away when not needed – like in winter or in the middle of summer.
SO there you have it!
I couldn’t be happier with this project.
I think this goes down as my favorite project of the year so far!
Nothing like having the pool to entertain the kids!
Other ideas for DIY solar pool heater
- Create a solar pool cover using a black tarp and hula hoops or pool noodles. We tried making these but the pool is way too big to make so many.
- You can also put the solar heater coils we made up on the roof facing south to capture as much sunlight as possible. It would just mean that you would need a lot of hose coming down and possibly control valves to control the water flow as needed (without having to climb up the roof everytime.)
Other Outdoor projects you might like –
- DIY Pool Side Towel Rack
- DIY Hammock stand using 3 tools
- DIY Raised Tiered Garden Bed
- DIY Ring Toss Game
See 22 other DIY Outdoor Project Ideas here.
Anika's goal is to inspire and empower beginners with woodworking, DIY, home improvement, and home decor ideas.
She wants everyone to unlock their creative potential and experience the feeling that comes with making something. Nothing feels better better than seeing something and saying "I can make that!"