Instructables

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.

 
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harari4 months ago

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 harari4 months ago

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

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

cudy789 harari4 months ago
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.
harari cudy7894 months ago
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)
glitch_inc4 months ago

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

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.

vladivastok4 months ago

GRT IDEA. JUST NEED A POOL, AND A FENCE, AND A LOCKING GATE. AND WHATEVER ELSE MAKES THE LOCAL CODES HAPPY. SORRY, JUST WANNA SWIM!!!!!!!!!!!!!!!!!!!!!!!!!!

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

bean.waxler10 days ago

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.

b1tbang3r3 months ago

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) 3 months ago

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.

steven48724 months ago

"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.

GardenGranny4 months ago

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_er4 months ago

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 WW4 months ago

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.

steven48724 months ago

"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%

BallscrewBob4 months ago

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.

rchauhan64 months ago
Hi great job! Was going to make one of these. Do you have any information on the wood burner?
leif.hietala4 months ago

Hi,

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?

swander4 months ago

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.

steven48724 months ago

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.

http://www.instructables.com/id/Overview-2/

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.

rayleb4 months ago

simplicity at it's best! kudos

Bard4 months ago

Really neat build.

Have you tried a pool cover?

kakashibatosi4 months ago

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

C-R-E-84 months ago
Nice made one with my dad last year and worked very well
rimar20004 months ago

Interesting design and well made.

Very good instructable.