Introduction: Solar Pool Heater

Picture of Solar Pool Heater

We got a small above ground pool for the kid's and so naturally Dad decided to find a way to heat it. Solar was the first step and a wood burning heater, the second step. Following is how I built the Solar Pool Heater.

The Solar Heater works by letting the water in the black pipe heat in the sun for one hour and then pumping that water into the pool (I found this takes about ten minutes). I installed it on my garden shed roof that is East West facing with a very shallow peek so both sides get sun almost all day.

Some of the Parts I used.

1. 300 ft of black 1/2" drip irrigation pipe. (three one-hundred foot rolls)

2. 12 volt dc utility pump (the connections fit garden hose quick connectors).

3. 12 volt Battery to run the pump (i had an old gel battery for a power wheelchair).

4. 12 volt timer with 17 programmable times ( off for one hour and on for ten minutes ).

5. 12 volt battery charger ( The plan is to replace this with a solar charger ).

6. Some 1/2" copper pipe; garden quick connection fittings; 1/2" PVC pipe and fittings; pipe clamps; wire and a roll of masons line.

Step 1: Join the Pipes

Picture of Join the Pipes

I wanted a way to join the three lengths of pipe with a smooth low profile this is what I came up with.

1. I cut a 1" piece of copper pipe and pushed it into the one end of the pipe to be joined. ( I let the pipe lay in the sun to get hot so it was easier to work with).

2. I then heat up the other end of the pipe to be joined with a small hand torch and then stretched it. ( I used the 1/2" end cap on the Wire Clamp Tool, which i made in one of my other instructables).

3. I then pushed this end over other end with the copper pipe in it.

4. Now I used the Wire Clamp Tool to make a clamp Joint.

I joined all the pipe before I made the coil because I pressurized the pipe with water to be able to make a good coil and make it easier to bind with the masons line.

Step 2: Make the Coil.

Picture of Make the Coil.

1. Used a garden hose fittings and old valves I had and clamped them to the two open ends of the pipe with hose clamps.

2. Connected one valve to the water supple for the yard and ran the water till all the air was out of the pipe. Then closed the lose end and then the end connected to the water supply so I had a water filled pipe.

3. Made the coil on a hard flat surface starting in the middle with the smallest radius the pipe would make without kinking.

4. Bind the coil in eight sections with some masons line as in the photos. I tied this off, melted the ends and added a cable tie.

5. Tied both ends of the pipe to the outer edge of the coil in the same place for the connection to the pump and pool.

6. Removed the valves and used an air pump to push out all the water in the coil.

7. Put in ninety degree barbed fittings on the pipe ends so they would not kink over the edge of the shed roof.

8. Any holes I patched with some electrical rubber tape.

The empty coil was easy to lift on to the shed roof.

Step 3: Connecting Pump and Timer

Picture of Connecting Pump and Timer

1. Connected two pipes to the ninety degree barbed fittings. One to the outlet from the pump. The other to an inlet pipe I made for the pool from 1/2' PVC fittings.

2. Used plastic garden hose fitting on the pump and pool to prevent corrosion from the pool chemicals. They fit nicely into the black pipe.

3. Used an old bucket with drain hole in the bottom for the battery and timers also to keep all the cables tidy.

I ran an extension cord from a Ground-Fault Circuit Interrupters (GFCI) outlet, for safety. Also have the timer for the pool filter pump in the bucket.

The heater has been working all summer so far with out any problems and gets some heat into the pool. It's nice for day swimming but for night swimming it's still a bit cold so I added a Wood Burning Pool Heater into the system.


andrefierens (author)2017-09-01

very nice !

I used screw joints , very easy !

andrefierens (author)2017-09-01

For safety reasons, I use a 12 Volt pump, with voltaic Solar Panel.

See and read

bybecker (author)2015-08-14

Hello. Just out of curiosity I ask: Placing a plastic film black floating on the pool water would not bring a better result, avoiding losses, since the heat obtained would be immediately transferred to the water?

andrefierens (author)bybecker2017-09-01

I use a solar panel to power the pump 12 Volt.

No Sun, pump stops.


DavidA310 (author)bybecker2016-03-08

absolutely, which is why they make black covers, but who wants to pull that on and off all the time, and pools look better when you can see the water. Pool covers essentially say: "neener neener, can't swim"

GregW19 (author)bybecker2015-08-22

damn your logic

harari (author)2014-08-06

very nice.

I have the same pool, it has a cover that looks like bubble wrap that is meant to heat the water. it works well, but there's no regulation. if you leave it too long its unbearably hot (and of course you can't use the pool while covered *rolling eyes*). i think i might try this with a thermistor and a controller to switch the pump on and off and keep a regulated temperature (maybe a check valve too, if the pump allows water to move through it when off). kind of like a sous vide cooker (which i made recently and got the idea from)

for night or morning swimming maybe some kind of electric heating (can run on a separate short loop with a switching valve to prevent energy loss)

only problem is i don't have a shed and my house is 3 stories high. might need a pretty strong pump..

Thanks for the idea.

harari (author)harari2014-08-06

BTW, why not use the same pump that filters the water?

cudy789 (author)harari2014-08-06

Filter pumps need to run 24/7 or else your pool turns a nice shade of green:( However I suppose you could install a switch or solenoid that can redirect the flow of the water from the pump for a few minutes to empty and fill the hose.

DebbieL104 (author)cudy7892017-08-14

Time to go to pool school or maybe actually own a pool! Not even pools in Florida need to run their pump and filter 24/7. The three main things that matter for proper daily pool pump run time are (and one of them is out of your control which causes the run time to change), and that is the actual daily high temperature. 1) one must have properly balanced pool water with the proper level of ones sanitizer of choice, 2) have a properly sized filter and pump, 3) run your pump and filter as follows:

4 Hours 70 to 75 Degrees

6 Hours 75 to 80 Degrees

8 Hours 80 to 85 Degrees

10 hours 85 to 90 Degrees

12 Hours 90 to 95 Degrees

14 Hours 95 to 100 Degrees

16 Hours 100+ Degrees

If you need to run you pump more then this then, the temperature is higher then you think, or your water is not properly balanced and sanitized, or your pump and filter are not the correct size to properly completely turn your water over once every 18 hours (best setup is 2 to 3 times in 18 hours). The filters and pumps on most above ground pools are usually the minimum to get by which forces longer run times. I am currently running my pool pump 10 hours a day and my pool water is crystal clear!

NOTE: For pools with algae problems, eliminate Phosphates! Add the proper amount of PhosFree to your pool, then start the weekly maintenance dose of Perfect Pool w/ PhosFree.

harari (author)cudy7892014-08-06

a pool this size doesn't need 24/7 circulation and filtration.
public swimming pools need massive filtration but the water is not still so circulation isn't that big of a deal, however, pumping all the water takes time, that's why the pump works all the time.
large private pools need less filtration because they are less active, but this means the water is still most of the time, once again, getting through all the water takes time.
pools of this size take about 4 hours to filter completely. to be on the safe side, and depending on how active the pool is and the type of use, 6 to 10 hours of daily filtration is more than enough, some filter for less with great results (myself included)

bean.waxler (author)harari2014-12-09

The pumps with those little pools are pretty wimpy. They are made for volume, but not pressure.

creektilghmank45 (author)2017-07-08

take some instructions from inplix to learn more about it

ssaedi (author)2016-04-24

Mami para calentar el agua

TinkerTailor (author)2016-03-13

Awesome, i made one but I live in Arizona where it gets cool at night and there are occasional clouds or shade. I also am not home does anyone here have a good source for a dawn to dusk switch or a temperature activated switch? everything i can find is a hundred or more and sized for a much larger system.

DavidA310 (author)2016-03-08

Also ... probably loosing a lot of heat due to convection. Make edging with 2X4's then throw 2 plexiglass sheets on top, then put pipe insulation (cheap) on the pipe going to the water. Those whose systems seem really inefficient are probably in cold, perhaps breezy areas.

DavidA310 (author)2016-03-08

Just doing the math here ... you'll have a more efficient system if continuously pumping. Efficiency goes up with a higher delta in the heating element (tube). For example ... with a heating element running at 210F getting water from 200F to 210F will take a lot longer than from 100F to 110F.

xdby54 (author)2015-07-19

What am I misunderstanding? How do you use drip irrigation without it leaking?

Elio23 (author)2015-06-30

I want to say thank you to you and other great insctructable who make me very happy. See my photo. Thank you so much, Elio from Italy

bean.waxler (author)2014-12-09

So does this not work if the water runs continuously? Because I tried this with 160' of black garden hose running over my houses roof, but the water only came out 2 degrees warmer and after 8 hours had only gone up by 2 degrees total.

jasoncattnz (author)bean.waxler2015-06-23

It makes no difference if the pump runs continuously or not. What will make a difference is if your hose is enclosed in a sealed box with a black backing and clear glass or plexiglass to let the heat in and trap it in. Simply running a hose around won't do much.

wiglaf (author)2015-02-09

Just a little something to remember, that I didn't see posted in the comments: the piping weighs in the neighbourhood of 90 lbs (just took the weight of 100' of generic 1/2" black irrigation pipe from Home Depot and multiplied by 3 for the 300' total weight) plus the weight of the water (+/-25.5 lbs), giving a total of roughly 115.5 lbs. Please make sure that the structure you put this on can actually handle that weight. Your pics appear to show that you've got your setup on the roof of some type of shed structure. You'll just want to maybe double-check that the additional weight you've put up there isn't going to become a safety issue.

Other than that, awesome 'ible. :)

MartinMakes (author)wiglaf2015-03-31

Thanks for your reminder about weight considerations when setting one of these up. Before setting it up I had confirmed that my shed could support the weight ( it has a steel internal frame ) but didn't mention it in the instructions. Thanks for your input and calculations.

johnfisher425 (author)2015-01-26

Great idea of using a solar heater! It helps a lot in saving us on our electricity bills. For more ideas on solar heaters visit here.

glitch_inc (author)2014-08-08

I wonder if you put a check valve on either side if it would self pump much like a coffee maker would.

bean.waxler (author)glitch_inc2014-12-09

A coffee maker heats from the bottom and pushes the water up. In this scenario, without gravity feeding the cold water, I don't think there would be a way to create a vacuum to pull the cold water up.

vladivastok (author)2014-08-08


bean.waxler (author)vladivastok2014-12-09

Find out what height you need to avoid the limit. Some places have them, some don't.

b1tbang3r (author)2014-09-09

I've seen a setup similar to this concept, except using metal 55gal. drums on a roof to gravity feed hot water for showers at a campground.

MartinMakes (author)2014-08-30

Thank you for all the comments and suggestion it's great to get all the feedback. The Wood Burner has been working nicely. I will be making the instructable soon.

steven4872 (author)2014-08-16

"I would like to apply something like this to a (much smaller volume; but hotter) hot tub. Currently the hot tub is electrically heated (expen$ive!)

To do this one needs to find a way to interface the solar-heated water with the existing hot tub water such that

a) There’s a flow from the heater to the tub when the tub is less hot than the solar heater and
b) Ensure water in the tub does not exceed (103° - 104°) by finding a way to control the interface so that the temperature stays within the 103° - 104° temperature range"

I don't have a hot tub but I would start by putting two tee fittings on you heater input and output. The Tee fittings would put the solar heater in parallel to the electric heater.

You can buy small mechanical temperature switches. Put one somewhere in the hot tub on on the water lines to and from the heater. This will turn off the solar heater if the temperature gets too warm. Add a timer so that the solar heater will not run during the night. Or instead of a timer you could connect the water pump directly to a PV panel so that the pump would only run when there is enough sun to run the pump.

the set the electric heater thermostat to less than the desired water temperature. This willl cause the electric heater to turn off at say 80F If the water is above or about 80 the electric heater would turn off and only the solar heater would run. You could also put the electric heater on a timer so that only runs when the solar heater is not available (at night ). You could also set the timer on the electric heater to turn it off when everyone is at work or school.

This would lower your electric heating cost and set you up for your next project, adding solar PV to cancel out all the power the solar pump and electric heater use.

GardenGranny (author)2014-08-12

My son made a similar one last year for his neices and nephews to heat their pool. It worked beautifully! Thanks for the instructible...very nice!

d_i_y_er (author)2014-08-12

Very nice instructable.

I would like to apply something like this to a (much smaller volume; but hotter) hot tub. Currently the hot tub is electrically heated (expen$ive!)

To do this one needs to find a way to interface the solar-heated water with the existing hot tub water such that

a) There’s a flow from the heater to the tub when the tub is less hot than the solar heater and
b) Ensure water in the tub does not exceed (103° - 104°) by finding a way to control the interface so that the temperature stays within the 103° - 104° temperature range

I imagine this can be done with some ingenious solenoid/thermostat arrangement.

Has anyone tackled this problem?

Bill WW (author)2014-08-11

Great design to use solar energy to heat water for any purpose, not just a pool heater. I like the large flat coil - simple but effective. Don't need fancy headers.

steven4872 (author)2014-08-10

"Evaporation carries a tremendous amount of heat away from your pool, and of course a dark cover makes the pool's own surface a collector too."

A pool cover doesn't need to be dark to collect a lot of heat. For a black pull cover the sun heats the black plastic, looses some heat to the air, and the rest is transferred to the water.

For a clear plastic pool cover, most of the sunlight goes right through the pool cover, That light then gets absorbed by the water. The light that doesn't get absorbed by the water then hit the bottom of the pool which is then transferred to the water.

It doesn't mater if the pool cover is dark or clear, both will heat the water while reducing evaporative cooling by 90%

BallscrewBob (author)2014-08-09

Great article and many people don't realise how much they can save by using methods like this.

When I built one of these a few years back I just put a "T" on the pools pump outlet with a valve so that I could control flow rates. It eliminates all the extra 12 volt items you have. Valve needs to be adjusted to just give enough pressure to initiate a flow.

Used mine an a blow up pool and then a larger above ground permanent pool

I had two with one feeding the next coil.

Then I just used a pool thermometer placed in the out flow to measure the temperature boost which could be as much as 25' C depending on the ambient temp and flow rate.

rchauhan6 (author)2014-08-08

Hi great job! Was going to make one of these. Do you have any information on the wood burner?

leif.hietala (author)2014-08-08


It's a good design overall but for the timer. Set the timer to have the pump on whenever there's sun on the heater.

When the heater gets warm, a lot of the heat is wasted to the surrounding air. Your efficiency will take a big jump if there's always cold water flowing through the heater; if the surface of the heater feels cool, then all the heat dumping into it from the sun is going where? Into the water. The water coming out of the heater won't feel hot, but its temperature will indeed be raised and your throughput of water will be much, much higher, and your net harvest of energy into the water will be greater. And that's the whole point. The water coming out of the heater won't feel as hot but there will be much, much more heat delivered to the pool on average.

Other suggestions regarding pool covers are very good. Evaporation carries a tremendous amount of heat away from your pool, and of course a dark cover makes the pool's own surface a collector too.

Add another 500 feet of hose and make your collector bigger. Sunlight is free and firewood is work. Do all the work on one weekend building the collector bigger, and keep the firewood for indoors, in the winter.

Add solar panels to run your pump. Then the pump only comes on when heat is falling on the heater: who needs a timer?

swander (author)2014-08-07

I got the same pool and the dark blue pool cover they sell for the inflatables (its like a huge shower cap) really gets the water warm on long sunny days, actually almost hot. I would say about 80. Keeps the leaves and flying bugs out too.

steven4872 (author)2014-08-07

I don't believe you need a timer. It the water flow is too low the coil will get hot and loose a lot of heat to the air. Pump the water too fast through the tubing it may act like radiator and not heat the water at all.

In a similar instructable they pumped water through the solar heater at about 1GPM continuously and at mid day the water cumming out was about 10F hotter than the water going in.

Your pump is rated at about 5 GPM. With 300ft of pipe you probably have 1 to 3 gallons of water in the pipe. Your solar collector might work well with the pump continuously on or maybe with one of the valves slightly closed down.

The other thing you can do is to reduce the heat lost by the pool through evaporative cooling. Using a solar blanket (basically nothing more than plastic bubble packing made with slightly thicker plastic for durability) . can be very effective specially in cooler climates. In hotter climates it may work too well.

rayleb (author)2014-08-07

simplicity at it's best! kudos

Bard (author)2014-08-06

Really neat build.

Have you tried a pool cover?

kakashibatosi (author)2014-08-06

What is the rise in temperature between intake and output on a regular sunny day?

C-R-E-8 (author)2014-08-06

Nice made one with my dad last year and worked very well

rimar2000 (author)2014-08-01

Interesting design and well made.

Very good instructable.

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