Pool Solar Heater or Optical Illusion for Entertainment




Introduction: Pool Solar Heater or Optical Illusion for Entertainment

Commercial solar pool heaters are expensive, especially if you need multples.  Here's how you can cobble together a solar collector/heater for your pool and create interesting 3-D optical illusions to entertain (or frighten) your neighbours and friends.

It's not as hard as it looks.  If I can do it, anyone can do it.

Step 1: Why Another?

There are a lot of pool heater instructions on the internets; this one culls together the best parts of each (sort of) and provides more specific advice for the pumping situation.

Step 2: Components

The solar heater consists of three main components:
  1. Pool water
  2. A pump
  3. Solar heater
The action is:
  1. Water is pumped from the pool to the collector
  2. The collector transfers its heat to the water going through it
  3. The heated (sort of) water is returned to the pool

Step 3: Components, Cont.

For this 'able, we'll be using two collectors and two input/output streams.

I started out with just one collector and wanted to try more for more heat exchange.

Step 4: Tools and Materials

The hardest (uhm, next-to-the-hardest) part of the solar collector system is getting the right materials and getting them to all fit together without becoming a Rube Goldberg project.

As we go along the steps, I'll show you more details about what specific parts were used.

Step 5: Tools and Materials, Cont.

(1) Pool (this Instructable used a 16 foot Intex vinyl above-grounder) [$330]
(2) 100 feet roll of 1/2 inch poly tubing per collector (total 200 ft per collector) [$10 ea]
(1) 8 foot 2x3 stud per collector (or 2x4) [$2 ea]
(1) 4x4 foot (approx) plywood panel per collector [$9 ea]
(1) Straight internal 1/2 inch coupler per collector (for coupling together into one 200 ft tube) [$1 ea]

(30) 8 inch or longer tie wraps per collector [$3]
(1) 1/2 inch T-splitter [$1 ea]
(1) 850 gallon per hour, 12 ft head, submersible pump [$70 ea]
(1) Slightly larger than 1/2 inch portion of rubber or malleable tubing, about 2 inches long (bib) [$1 ea]
(1) small hose clamp [$2 ea]
(n) Bottles wine [$3 ea Europe, $9 ea North America]

5/8 inch or larger drill bit (for holes through which to pass cable ties)
Scissors (for lobbing off 5-inch splice to connect T coupler to pump output)
Duct tape (for patching holes in hose)
Slot screw driver (for hose clamps)
Wine glass

Step 6: COLLECTOR: Base

We'll start out with building the collector since that will give you an idea as to whether you want to continue with the rest of this nonsense.

Get a 4x4 sheet of plywood for each collector.
You can buy 4x8 sheets at the hardware store and have them cut them down to size for you.  This is advised because it is easier to transport back to your house.

I got one large sheet of plywood at the local Habitat for Humanity ReStore, and the other already pre-cut as as an under layment board.

Paint the bases black and set a side.

UPDATE: using reflective material rather than black paint may be better for heat transfer.

Step 7: COLLECTOR: Frame

Cut a 2x3 board in two four-foot pieces, then attach them in a cross-piece.  You can spray paint it black if you want, but it'll mostly be covered with black hose anyway, but eh whatever.

  • 2x3 is a little lighter weight than a 2x4, but use whatever you want
  • Two four-foot pieces for the frame is the right size for 200 feet of hose, or one collector
  • This smaller, four-foot size frame  is easier to carry and manage and thus put away at the end of the season (and move around)
  • You can attach the two sections in several ways, none of which is any better than another (I tried several methods, the easiest was just to pound 'em into each other)

Step 8: COLLECTOR: Collector Piping/hose

The collector's guts consist of a lonnnnnnnnng black pipe through which the water will run and (hopefully) heat will transfer to the water.

This is the type of hose that I bought.  It's cheap. It's black. Those are the only good qualities about it.  Two hundred feet of 1/2 inch diameter piping will fit on the frame.  This was found near the plumbing department in the irrigation and sprinkler aisle and was only sold in 100 and 500 foot rolls.

This stuff is about $11 for 100 foot, so buy two rolls for one collector, buy 4 rolls if you want to build two collectors.

FYI: why this stuff and not copper?  I don't have any skill and putting copper pipes together sounded like a pretty big hassle. Plus I wanted to mimic the commercially available solar collectors as much as possible which for the most part are based on some type of black hosing.

Step 9: COLLECTOR: Piping Coupler

Since I used two rolls of piping, I needed to couple them together.  These little gray plastic things that have ridges on the end worked perfectly for this.  They were found in the same aisle as the hoses.  Again, if you are planning to make two collectors, grab at least two for this part.

  • There are different sizes and widths of these little gray plastic things so be sure to try it out on your hose while at the store to make sure it will fit.
  • The guy at the hardware store told me to use a hair dryer to ensure a tight fit, but my hair wasn't even wet so I don't know what the hey he was talking about.
  • He also said I needed a hose clamp but I didn't, so call the cops

Step 10: COLLECTOR: Piping Unwind

The hose is pretty kinky (but not in a good way).

So first unravel the hose as much as possible.

Step 11: COLLECTOR: Piping Winding

The idea here is that you will be winding the pipe on top of the frame around and around, similar to piping frosting onto the top of a cake.

But you'll want to leave about ten feet of hose dangling before piping.  (So this is akin to piping frosting on your table first and then continue up and onto the top of the cake.)  

WHY? You'll need the dangling 10 feet of frosting er I mean pipe to run the water to/from the pump and pool.  You'll need to remember to do this for each end of the hose.

Step 12: COLLECTOR: Piping Winding, Cont.

You can start the piping at the outer edge of the frame and wind around, or at the center.  I did both and neither was easier than the other.

In this photo I had started from the center and wound outward.  Either way the hose will kink every 10 seconds.

Step 13: COLLECTOR: Piping Winding, Cont.

As you frost, you'll want to use plastic wrap ties to keep the hose in place.  I used 8-inch ties (a total of 30 for one collector with 200 feet of pipe). 

There are several conflicting comments about the use of tie wraps; if possible you might want to get wraps that are specifically designed to handle sunlight.

Step 14: COLLECTOR: Piping Winding, Cont.

The tie wraps  I used were kind of short (8-inch long) and allowed me to hitch up only two wraps of pipe at a time.  You might want to get longer ties.

To wrap,
  1. Drill an initial 5/8 inch hole through the frame and right along the inside of the first loop of frosting,
  2. Then drill another hole on the outside of the second loop of frosting.
  3. Run your fingernail along the tie wrap to double-check where the teeth are, then feed it through the two holes. WHY? Tie wraps have only a one-way attachment and 99% of the time you'll get them backwards.  By running your fingernail along the wrap you can reduce the percentage of frustration.  Some times.

Since my tie wraps were pretty short, I actually had to use pliers to tighten the wraps.

Here is an mp4 showing (in olde thyme speed) tie wrapping a piece of the hose.


Step 15: TIP: Drilling Tie-wrap Hole

Don't get too close to the outer pipe when drilling the hole.  Yep been there done that.

Try not to touch the drill bit too much.  Yep been there burned that too.

Step 16: Alternate to Tie Wraps: Screw Heads

I saw a few collectors on the Internet where people used screw heads to act as clamps to hold the piping down.  This didn't work too well for me because the screw heads just weren't large enough.

For me, the tie wraps just worked better.  And they hold better when moving the thing around.

Another idea for holding down the collector tubes would be to use long copper strands and/or string in a weaving-manner; i.e. poke the string/wire in and out through the holes.  This would be nice because it would allow you to easily remove the string/wire at the end of the season and breaking everything down.

Step 17: COLLECTOR: Piping, Cont.

When you get to the end of the first reel of hose, use the gray coupler thing to couple to the next roll and repeat with the second hose.

Then I guess you're supposed to wash your hair and dry it with a hair dryer.

You can skip this step, of course, if you already had a 200 foot roll.

Step 18: COLLECTOR: Piping, Cont.

No matter what you do, you will end up eventually with an optical illusion.  

You can stop here and put it on display or continue to unkink, unwravel, unwind.

Unwind with a glass or two of wine at this point.  This will actually make the hose look straight.

Step 19: COLLECTOR: Piping, Cont.

As you near the end of the roll of piping, be sure to leave about 10 feet or so unwrapped for water access to/from the pump/pool.

And watch out for kinks.

Being able to do yoga poses is also useful to hold down the hose between tie wraps.

Step 20: COLLECTOR: Repeat for Secondary Collector

Eventually, after enough bottles of wine, you'll have two collectors.

Place each on its plywood base.

This photo almost looks like I knew what I was doing.

Sort of.

Step 21: PUMP

I started with a low-cost ($30) submersible garden fountain pump. That worked well for one collector but not for two.  So I got a larger ($80) pump.

This one is rated at 800 gallons per minute.  Seems to work and it seems like I could add another collector and it might still chug along.

This pump was chosen because it had specs that were right on the package:
  • Pumping height: 12 ft (means it can get the water up and out of the pool okay)
  • Fits 1/2 inch tubing (means it should fit my hoses; more on that in a bit)
  • For ponds up to 12 ft (my pool is a little larger than that, but eh not by much)
  • Had a bunch of parts that looked like they could be useful (more on that in a bit, too)
  1. I wanted to experiment and the Intex pool pump was too much of a hassle to disconnect and reconnect
  2. The hoses coming to and from the Intex pool pump were huge and I knew that it would be another hassle to try to fit those hoses to the collector's tubing
  3. I wanted to experiment with a timer to turn the collector pumping action on and off every 30 minutes or so and I knew that the Intex pump would probably throw its circuit breaker and ruin my experiment
  4. I was not planning on introducing a thermo-syphoning technique
  5. If this whole collector thing did not work then I planned on using the pump for a fountain feature

Step 22: PUMP: Tip

Just in case you are unfamiliar with pumps, this one is submersible so you actually place it in the water.  Some pumps are not submersible (i.e. outmersible).

The input of the pump usually looks like the intake of a B-52, with nasty looking propeller things.  The output hole (hee hee) is usually just the other end.

Step 23: PUMP: Attach Collector Hose Ends to Output End of Pump

First attach a T splitter on the pump output (depicted in the pumptoon) that will BOTH:
  1. Fit on the pump's output hole (hee hee)
  2. Fit the 1/2 input piping on the collectors

H A   !

Step 24: PUMP, Cont.

There a few types of T splitters that are made for 1/2 inch tubing.  Both, according to the guy at Home Depot, require you to wash your hair and then dry it, but I didn't.  I opted for the little grey splitter since it was the easiest to use.

Step 25: PUMP, Cont.

While the little gray T splitter's output fit into the two inputs of the collectors' pipes okay, the input of the T would not attach to the pump's output hole (hee hee).

This is because the pump's output hole (hee hee) is hard plastic and the little gray T splitter could not get a grip.

Step 26: PUMP, Cont.

Therefore, the next contortion is to cobble together a piece of the 1/2 pipe, connect the 1/2 inch pipe to the little gray thing's T input, then cobble the 1/2 inch piece of pipe to the pump's output hole (hee hee).

Even though the pump's specs said that it "fits" 1/2 tubing, it doesn't say that it will fit as-is.

So depending on whether the object in question is a hose, a tube, or a pipe, the "specs" will apply to either the inside diameter or the outside diameter.  No word, however, on what the specification is for an output hole (hee hee).

If you wash your hair at this stage and use a hair dryer you might be able to make the tubing pliable enough to squish on to the output hole (hee hee).

Step 27: PUMP, Cont.

So the next contortion is to cobble the 1/2 inch pipe through a bib and then to the output hole (hee hee) of the pump.  A bib is an external coupler and I just made up that term.

The bib consists of a piece of tubing just slightly larger than the 1/2 pipes.  Go to Ace hardware with your 1/2 inch tube and they'll be able to get you an inch or so length of bib.

Step 28: PUMP, Cont.

And add a hose clamp around the 1/2 inch pipe.  You might not need the clamp, but you probably will so I recommend it.  You don't need to dry your hair.

Step 29: PUMP, Cont.

After about a half an hour, this is what I wound up with:
  1. Coming out of the pump is a 1/2 inch piece of piping coupled to the pump's output hole (hee hee) with a bib and clamp
  2. The 1/2 inch piece of pipe is connected to the input of the T splitter
  3. The T splitter outputs will go to the inputs of each of the collectors' pipes


From each collector, grab one end of its hose and attach to one end of the T output.


Almost done!  Toss the pump into the pool and plug it in.


Grab the other end of the hose from each collector and place over the edge of the pool.  This is where the heated (sort of) water will be pumped to after circulating through the collectors.

Step 33: (OPTIONAL) Add Thermometer

Add a thermometer to one of the collectors.


I snagged a few huge windows at our local Habitat for Humanity ReStore for $10 each.  I just laid them on top of each collector and shored up the sides with a few loose boards to keep the wind out.  

I didn't build a complete window frame because I wanted to be able to disassemble, remove it, and store it over the winter easily. Plus I'm too lazy.

The collector boxes really DO need to be insulated, so if you are planning on this type of collector, building up a frame would be worth it.  You don't have to do it immediately if you are lazy like me, but try to get around to it before the season is over.


On a pretty warm day (80ish) the collector (under glass) displayed about 120 degrees.


As an experiment, I wanted the pump to circulate every 1/2 hour so purchased a timed socket.  This allows the water to sit in the collectors for a while to warm up before getting pumped back into the pool.  Or that was my theory, anyway after discussing the approaches with the experts at work. (snort!)

I went through two of the Brinks timers because the timers stopped working after 1 day.

I settled on the GE timer which actually allows you to set the time in 15-minute increments.  Jury is still out on this one.


Step 37: FINIS

So how's it working?
Well, as soon as it was up the clouds came rolling in.
And it's been almost raining every day since.


Some final tips for pool heating ideas:
  1. The commercial solar pool heaters are expensive but convenient.  They also require you to put them in line with the pool's filter and pump (they usually do not have their own pump).
  2. There are many on-line calculators out there (see this one for example) that will help you determine the number of collectors you should use. The number of collectors that you need will always be more than you are willing to build or buy, but it will usually come to about 5 collectors.  With the commercial heater that I started out with initially (see photo) I have a total of 3.
  3. A good example of solar collector system: Filpumps
  4. Get and use a solar blanket as a cover.  (See this instructable for easily putting on and taking off the cover.)
  5. Get a way to mix up the water (there is a gadget especially designed for this but I can't seem to find the link). Mixing up the warmer water on top of the pool with the cooler water at the bottom of the pool results in a better overall temperature.
  6. By the way, I am using this for my chlorine production: Intex Salt Water Pump
  7. A possible chlorine replacement (thanks to member ebb_au): Biguanide
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    2 years ago

    I wish I had seen this before I built my heater! I picked up 2 round wire rolls from the curb and placed roofing material on them, then coiled my garden hoses on top. I use a Beluga, instead of a pump. The water coming thru the hose into the pool on a sunny day is 120* which keeps my 14,000 gallon pool over 75. This year I will add a box around the hose & a clear cover, hoping to get it warmer. I may get a solar cover to help keep the heat in at night.


    3 years ago

    I've constructed a PVC pipe heater like yours but it is not flat, it is in the form of a cone. It is lying flat next to the pool and because heat is rising as we all know the hotter water rises to the top of the coned heater and is circulating without a pump into my above ground PVC round pool. The cold water outlet is lower than the hot water return inlet on the pool. Therefor no pump is needed. Pumps are pumping too fast and does the water not getting hot enough in the heater to be effective. As water is heated in the coned coil it obviously flows at its own tempo out the top of the coil to the pool. On top of it all I've got a pool cover covering even the sides of the pool that assists in warming the water even more.


    4 years ago

    Nice! Gave me some ideas...

    Trying it soon; but with some mods. I am using dark garden hoses for the piping. I intend to use PVC instead of wood to mount (zip-tie) the hose(s). There are 4-way fittings that will allow me to mount 3 100' hoses along a 10' piece of PVC Pipe, using a similar "cross" pattern..

    I will be mounting on my roof (2-story) for maximum heating.

    I am going to try using 'thermo-siphoning' to move the water. Since it is a garden hose, I will prime it with my water hose, and see what happens! I have a pump if that fails...

    I will take pics as I go, and if successful, create an Instructable!


    5 years ago

    Genius ! Nice Pictures !

    I build a Solar Water Heater, first with a garden hose and a Solar fountain-pump.

    I still use a Solar fountain-pump ( SolarMax 600 - Ubbink ), but with a Intex Solar Mat. Which makes the module, system Foldable and Portable. Info click :



    7 years ago on Introduction

    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


    8 years ago on Introduction

    I have done this myself for the past couple of years.

    get one of the utility pumps used for flooded basements, that have a garden hose attachments. buy the thinist, cheapest garden hoses you can find, 2 or 3 of them.

    buy an outdoor timer with setting of 15 min or less off on cycles and plug the pump into it. water will almost boil coming out of the end of it.



    8 years ago

    I intend building one of these. kinks seem to be a big hassle when winding. However if the coil is filled with water and sealed ( tied kink at each end) I think kinking will be greatly reduced. You can actually bend copper this way without in kinking - I have done it - as water is non compressable - unlike air. Great detailed job BTW ; good pic etc prob helped by wine!


    8 years ago

    bib is a TLA for " bit in between"


    8 years ago on Introduction

    I built one very similar to yours except I used 1/2" garden hose inside an insulated box with glass over it. In my area(NE Ohio) ,we don't have enough sunny days to heat the water very much. A pump that circulated 1 gallon a min brought the water temp up the best maybe 20 degrees.


    8 years ago on Step 38

    Do you think it would be possible to use a small DC pump powered directly by a solar panel? It would only run when the sun is out and pump faster the more sun it received.


    Reply 8 years ago on Introduction

    That'd be a great idea-- it would depend on the horsepower/GPH of the motor. The A/C motor I'm using is 800GPH, for example.


    8 years ago on Step 8

    Thanks a lot, very useful!!!


    8 years ago on Introduction

    Here's a less expensive way: drape black plastic just beneath the surface of the pool (assuming you don't want to paint the bottom of the pool black. Now your heater collect is as big as your pool and more efficient than any other design (96% because the only loss is the reflection from the water surface). Split large black plastic garbage bags can be used, but I don't know how to easily connect them to make a large sheet. To make it up to twice as powerful, place 4x8 aluminum-sided insulation boards on each side of the pool where light can be reflected into the pool. $12 for each 3 m^2, 20 times cheaper per watt than this method.


    Reply 8 years ago on Introduction

    Yah, I saw something like this in this 'able:

    But actually when doing research, I didn't find that to be a popular option. Have you actually tried this and found it to be effective? It would be a great alternative if so.


    Reply 8 years ago on Introduction

    We have a 4x8 foot inflatable pool where I have split black trash bags and added the reflectors. But the physics are simple enough that calculations are more accurate than DIY comparisons. The lily pads you link to are better per square foot than any plastic pipe method because the heat transfer through the thin plastic is better and there is no loss in transfer to and from the pool. The lily pad method would be better if they were below the surface of the water by at least 6 inches. It is losing heat from its surface being hotter than it would be if it were sunk. The ideal method for winter would be to have painter's plastic sheets (clear polyethylene, very inexpensive) or the clearest greenhouse plastic you can find to lay on top of the water's surface., then have a sunken black plastic layer, or, less optimal because more heat into the soil, the bottom and sides black. Then add reflectors to the north side for midday and to the west side in morning and east side in afternoon. Amount of temperature increase is 6 kWh per m^2 per day for the yearly average of most U.S. locations, times the m^2 of the pool if it is summer which is still correct in winter if you use reflectors, times 96% for 4% loss from the top plastic (8% if it does not lay on the surface of the water), divided by heat capacity of pool which is 1 degree Celcius per calorie of heat per cm^3 water times m^3 volume of pool water times 1E6 cm^3/m^3 times 4.184 Joules/calorie times 1/3,600,000 kWh/Joule. If 18x30' pool averages 4.5 feet deep (meters: 6x10x1.5= 90 m^3) this gives:
    6 kWh/m^2/day * 6x10 * .96 / ( 90*1E6*4.184*1/3.6E6)
    or to simplify canceling the large numbers and the pool surface area:
    6*0.96*3.6/1.5 depth/4.184 = 3.3 C increase during one day which is 6 F. Plus or minus any gains or losses from the hotter or cooler ground and air. If pool is kept same temperature into fall, then there will not be much ground heat loss compared to the surface. If aluminum-sided 4x8 insulation boards were used as the reflectors, then you flip them down to cover the pool when Sun is not shining (aluminum side UP, important). Heat loss in watts is ft^2 surface * F temp difference divided by R-factor divided by 3.4. For 6-hour sunshine day R-factor=0.5. When insulation R=4. These are underestimates if the water is still which is maybe R=2 from the water itself insulating. So watt-hour loss per day for 50 F day for 12 hours and 35 F night and 85 F pool is (30x18)/3.4*{6 hour*(85-50)/0.5+6 hour*(85-50)/4 + 12 hour*(85-35)/4} = 100 kWh per day. If the reflectors kept an effective pool-area exposed to the Sun, then the pool's 6x10 m surface gained 5 kWh per m^2 (winter) or 300 kWh per day for the pool, 3 times more than the heat loss. Even with 30% cloudy days and 30% shade from trees, 85 F pool throughout winter for 80% of U.S. should be "easy" by this method....with enough reflectors (20 4x8 insulation boards in this case, $11 each) aimed moderately well throughout the day which is a reason I did a heliostat instructable. Even without reflectors, a pool painted black and covered at night (to prevent evaporation which kills the heat gain) will get hotter than a shallow pond in a few days, over 100 F in the summer.


    Reply 8 years ago on Introduction

    Well it's been about thirty years since my theromodynamics class but the main idea of the submersible pads would be much less deep than other rabbit holes I've been down. Might give this a try next year.


    8 years ago on Step 38

    I have thought about this method. Right now I have been using a solar blanket for several years. From mid June through mid September my pool temperature runs about five degrees below the outside air temperature when the cover is left on except when the pool is being used. In late July and August we have to uncover the pool in the afternoon or the water temperature will be close to 100 degrees!!! Not to refreshing when you've been mowing the yard!


    Reply 8 years ago on Introduction

    Wow; I used a solar blanked too but never saw the temperature rise to more than 79, and that's with the solar collector pumping.


    Reply 8 years ago on Introduction

    I live in the Texas panhandle. By ten o'clock in the morning from mid June through the end of August it is usually ninety degrees or better outside. I have full sun exposure on my pool during those months from 10:00 a.m. through 7:00 p.m. with the overnight temperature averaging just above eighty degrees. My pump is on a timer and doesn't run at night. I think a solar collector running at night would act as a heat exchanger pulling heat out of the pool if the ambient air temperature is lower than the water temp.