Solar Water Heater for Pool





Introduction: Solar Water Heater for Pool

This is the pool that sucks up massive amounts of propane to keep it at the preferred temperature of 80+. Last year I did an experiment with 50 feet of 1/2 inch black polypipe coiled on a board to test the solar hearing theory. The test was successful so here is my integrated solar heater instructable.


Relatively inexpensive. The most expensive pieces are the 2" ABS sections and the PVC pool fittings. All in I spent about $100. $50 in fittings and $50 in other bits and pieces.


Chop saw, drill, drill bits, glues and a custom made thread cutter for the ABS.

Step 1: Select Your Point of Entry

The 1st thing to figure out is where you will cut into your pool system to install your heater. Most pools have 1 main return to the pool, so you will need to cut that open to create your solar system access. My pool happens to have a splash pad with 3 independent feeds all with separately controlled flow valves. I cut into the centre water feed that just happens to run into my pool house on the end. As you can see from the pic it is just a normal 2" PVC pipe. I cut out about 3 feet of pipe to create my bypass.

You will need the following parts for this section of the build.

2 x 2" PVC flow control valve

1 x 2" PVC coupling

2 x 2" PVC T junction

2 x 2" PVC 90 degree elbow

PVC cement

Transition cement

Section of 2" ABS pipe

Plan out the pieces and test the fittings for size before glueing them together.

In my example the main flow valve is open and the solar flow valve is closed. The solar system would not be running. By opening the solar flow valve leading to the solar system you allow water to start circulating into the solar system. Close the main flow valve to force all the water into the solar system. For those of you that only have 1 pipe going to your pool you may want to have some water still flowing directly. Keep in mind of too much water is put through the solar system it flows so fast that there is very little time to pick up heat. A steady slow to medium flow is best for the solar system.

Step 2: Bring Your Pipes to the Roof

In this step you will extend the pipes to the roof. You will use 2" ABS pipe now, as it is less expensive and it is black to attract the sun and heat.

Use transition cement to connect the ABS to the PVC elbows extending them up to approximately 4-6" below the roof line. Add 90 degree elbows and run the pipes to approximately 4-6" past the roof edge. In my pics I run the pipes to the side of the roof as there is an eavestrough on the lower roof edge. Add more elbows and straight pieces until your pipes are on the roof ready for the solar heater system.

Step 3: Build the Solar Assembly

This part can be scaled up or down to suit your needs. You can use anywhere from 8 to 16 pieces of 1/2 inch polypipe to create the heating assembly. Minimum of 8 pieces to allow for the flow of the water going from 2 " to 1/2 " pipes. The import thing to remember when designing the system is to have the water flow UP the roof. If you try to go sideways along the roof then the bottom lines will fill and the upper ones will not have water flowing through them do to gravity and pressure. By having them flow up that will all fill equally and flow at the same rate to the top of the system. They then dump into a 2" collection pipe and are carried back down to the pool system.


10 x sections of 1/2 inch poly pipe

20 x threaded barb connection for 1/2 inch poly pipe

20 x hose clamps (small)

2 x 6 foot sections of 2 inch ABS pipe

2 x 2 inch ABS caps

In my example I used 10 pieces of poly pipe, each piece is 10 feet long. They are spaced out about 8 inches between each pipe. To create the connection between the 1/2 inch poly and the 2" ABS I did a bit of a McGiver job. I drilled into the ABS every 6 inches using a 3/4 inch bit. I then created a thread by using a home made pipe thread cutter. Buy a 3/4 inch threaded black iron fitting and take a grinder to it to cut grooves into the fitting. The edges of the grooves will easily cut a thread into your holes. As it turns out the threaded barb connections for 1/2 inch poly pipe have the same thread as the black iron fitting.

Once you have tapped and threaded all the holes wrap the poly connection in teflon tape add a few drops of gorilla glue and thread it into the 2 inch pipe. Be very careful as there is not are not a lot of threads holding this in place. Enough to make it work but no extra. I also used PL construction adhesive on the connections for added strength and to make a firmer seal.

To join the poly lines to the barbs drop 2 hose clamps onto the line then heat the end gently with a low flame propane torch. Just enough to make it soft. This will allow you to insert the pipe onto the barb without too much pressure. Once you have all the lines attached time to bring it to the roof.

Connect the rest of your pipes, tighten all hose clamps and screw the polypipe down with clamps and steel roof screws. I also used aluminum hanger to secure the main feeds to the roof. There is a 1 to 2 degree (C) 2 to 4 (F) difference between the feeds to and from the roof. Enough to make a difference. Brought my pool from 75 to 80 in the 1st weekend.

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    36 Discussions

    Your concept of the solar pool heater is fine, but did you do any research? it would be easier cheaper in the long run and more cost effective to purchase a prebuilt unit and install it yourself. That this is badly engineered and with the wrong materials and if you haven't done so already you will kill your pool pump I didn't see that you mention a check valve or flow meter this will be; and is a "hot mess"... hopeful the building inspector in your area doesn't see it and pay you a visit and don't try to sell your house with this on it everyone will be telling you to rip it out if it still is working... lol

    4 replies

    I very much doubt I could find anything that gives me 1.5 to 2.5 degree temp increase for less then the $100 I spent on this system. Hot mess??? Might not be pretty but it works. No idea what you're talking about with the building inspector comment. 1st of all this would not fall under any kind of bylaw and there is nothing unsafe about it. If you actually READ the 1st step you would see that I have complete independent flow valves for all parts of the system, so unless I decided to close ALL my valves and run the pump your comment about "killing the pump" has no basis in any facts. Try understanding something before you make a bunch of comments about "bad engineering".

    This design does work but TonyF65 is right. If you look you can find efficient pre-built solar panels pretty cheap. I bought six 2'x10' panels and wood to build a rack to mount them on. Total project cost me about $300 but my pool is larger than most. I'm running about 28,000 gallons of water and pushing 55 gallons of water per minute through my panels. They are so efficient I actually have not used my propane furnace in 3 years. I'm in northern Minnesota but even with our sunlight it raises the temp in my pool about 6-8 degrees per day. When we get stretches of hot days and the kids are in the pool a lot I find I have to run it at night also in order to help cool the pool back down. Last summer there were a couple times that the water temp in the pool were 94 degrees and while that sounds awesome, it's actually not even refreshing to swim in it at that temp.

    I guess you can say the same about every instructable in this site. Go out and buy something. The whole point of this site is to make it yourself, or at least that's what I thought. :)

    Good point! I'll admit that I lost sight of that. Thanks for the reminder. That being said I'll throw this out there for another solar idea on the same lines as this that I did years ago on one of those little pools with the inflatable top ring. I had a spare water pump (1/2hp shallow well pump) and I attached a short garden hose and put it in the pool on the suction side. Then on the exit side of the pump I attached as much garden hose as I had available. Weaved that hose back and forth on the lawn as every turn cause the water to 'rub' up against as much hose side as possible and then the end of the hose went back into the pool. On a warm sunny day the water returning to the pool was quite warm. Didn't take long to heat the pool up so the kids were happy.

    Please don't be discouraged by all the wanna-be engineer comments. Keep on building and dreaming.

    1 reply

    LOL, no issues, will always try my thing. People can see and make comments, good or otherwise. There's always more to learn and build. :)

    Years ago a friend of mine in Auckland, New Zealand who had an inground pool used several big coils of black alkathene plastic pipe laid flat on the roof of his garage coupled to the pool pump to heat the water.

    I think he said he had about 500 metres of pipe all told.

    He used a floating pool blanket when no one was using the pool and he told me that he was able to extend their use of the pool by several months.

    I don't remember the size of the Alkathene tubing but think it was 1 inch diameter. Also not sure whether the coils were connected in parallel or in series.

    While such a setup is not as efficient as a proper solar pool heater it certainly does work and is not too expensive to set up.

    1 reply

    OMG - 500 METERS!!!! That is 1 massive project. Good for him. Way too ambitious for my little pool. :)

    I don't think that a certain flow rate is critical. Any heat that is absorbed by the tubes will be absorbed by the water flow through it and will contribute to raising the temperature of the pool water. If the tubes get warm to the touch some heat may be lost into the air.

    1 reply

    I agree, the flow rate would not make that much difference in the overall efficiency of the system. Slow lets the water pick up more heat but delivers less water overall, faster picks up less but delivers more water over the same period of time.

    I have built one with 220' +/- 1" polypropylene. It came from a well that I had just abandoned. Mine just lays on a dark colored tarp in front of the pool. I want to build a system with an arduino to control solenoid valves on the heater and bypass to control temperature. Unfortunately the valves that I am finding are just too expensive. As it is now the water coming out when the heater is first turned on is too hot to touch. In a perfect world I could use a normally open valve for the bypass and a normally closed valve for the heater. That way I could energize both when the heater is hot enough and de energize both when the water is too cold.

    2 replies

    If you ever find an inexpensive auto control valve let me know. I would very much like to automate the system if it ends up being worth it. So far I have definitely been saving propane with the solar system. It's not the prettiest system but it definitely WORKS. 1.5 to 2.5 degree temp increase depending on how hot the roof heats up. I may end up at one point doubling the pipes.

    I am currently looking at an irrigation valve. I can't find all of the info I need on them. I see that they require 24 Volts but they do not give the current. They can apparently take 120 F.

    Could you post flowrate and input/output temperature, so we could calculate power? I doubt this configuration is efficient because the small surface area (sun is 1000 W/m2) and plastic is a poor heat conductor.

    4 replies

    I've posted the temp rise a few times, 1.5 to 2.5 degrees. Flow rate where? The flow rate in the 2" pipe is much faster then the flow rate in the 1/2 in polypipe. It's also completely adjustable. The solar unit is tied into the centre or the three splash pad returns. Look at the picture of the pool and you will see the splash pad. I can have the flow gentle or blasting 18" up above the pad. The more flow I direct into the splash pad the higher the flow rate to the pad and the lower the flow into the 2 pool returns. I tend to keep it on the gentle side, unless the Grand kids are visiting, they like it blasting!!! :)

    Flow rate of the full circuit (in 2" pipe). Then there is then a formula that give you the power captured into water.

    We are working on a coroplast based solar heater (simpler, cheaper and more efficiency than tubes). Today we produced more than 600W of power with only one square meter!

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    That's awesome. I was thinking the exact same thing after I built this. There's a nice UV resistant dark tinted sheet that would work very well. What did you do to create the fittings for the end of the coroplast? I would love to see the design you came up with. I have some designs going back a few years for exactly this sort of thing, just never had the time or inclination to create a prototype.

    We tried different glues and configurations. It take more than one year of work to finally find a solution and without glue (cheaper and last longer). We are writing a tutorial, you will be surprise how it is easy to do. Subscribe to our newsletter to receive updates.