Introduction: Pool Solar Water Heater

How to build a solar pool water heater.

Step 1: What You Will Need

When you live in Canada, you need to turn up the heat in your pool all summer long if you want to use it.

First off, you need a location to install the heater. Preferably, if you live in the northern hemisphere, a southern exposition. The location should have as much sunlight as possible all day.

That said in terms of supply and tools , you will need:

L shape metal rods (or wood it you prefer)
2 x 64 inch 1 1/4 inch diameter copper pipes
3-4 rolls of 1/4 inch copper pipes.
Tin solder
Soldering paste
Welding torch (bernzomatic, plumbers stuff)
Pipe cutter
Chalk line
Automatic punch
Measuring tape
Broom stick
Acetone or other cleaner that can remove soldering paste
Plumbers tape

Step 2: Making a Frame to Hold the Pipes

I think you could probably builds the frame out of wood or other material. I decided to build this with L shape steel rod.
Cut the rods to length to make a rectangle. on the shorter side , I made some notch with a hole saw, so the pipe will fit in. Weld the rectangle together. If you don't have a welder, or access to one. You could also drill and bolt the part together. I used some rubber to isolate the steel frame from the coper to prevent metal reactions.

Step 3: Drill the Manifolds

Drill 1/4 inch holes in a straight line into the 1 1/4 inch pipe to make two manifolds. I made holes every other inch for a total of 63. In order to make a straight line, I used a chalk line.
insert the pipes onto the frame so you can evaluate where to start and stop drilling holes.
This way you will not have any holes where the manifold pipe will attache to the frame.

I have evaluated the 63 1/4 pipes will have more then 3 times the diameter of the 1 1/4 " pipe. this is to make sure the water will slow down a bit in the smaller pipes.
By slowing down the water a bit , It helps with the heat exchange...

Step 4: Drilling

I made a jig to align the pipe onto the press drill. Pre marked and punched the pipe every inch.
Just drilled away 126 holes. (63 per pipe).

Drills don't make perfectly round holes, so use a hand borer tool to make it rounder, and made it to fit as snug as possible for the 1/4 pipes.
try and fit every 126 holes with a sample pipe.

To make a perfectly straight line on the pipes, attache them together with clamps , then use a chalk line where the pipes touch each other.

Step 5: Cutting and Fitting the 1/4" Pipes

Unroll and cut the 1/4 inc pipe. Make a jig, and try to make the pipe straight while unbending it slowly onto the jig. I suggest you mount and secure the 1/14" pipes to the frame. Make sure the distance is the same between both pipes.

Cut to the 1/4" pipes so that they are about 3/4" longer then the distance between the to 1 1/4 pipes. This will ensure, once you insert the small 1/4 pipes into the holes of the manifold pipes, that there is a bit more than 1/4" exceeding inside.

Step 6: Prepare for Soldering

Like any plumbing job involving copper pipes, you must prepare the copper very well.
Take a medium sandpaper, and sand any oxidation everywhere you will have to solder the pipes together.

Sand inside the 1 /14" pipes. attache some sanding paper using double sided tape on a broom stick and sand the inside in line with the holes. this will get rid of the drill shrapnel and will help the thin to make a better bond.

Sand all of the 63 1/4 pipes end. (about one inch on each end)

Step 7: Assembling the Small Pipes Into the Manifolds

Insert every 1/4" pipes into the holes on each side. insert the small pipes into one side, then back into the other side. you can insert a piece of wood to align the pipes inside.

Step 8: Soldering the Pipes

Apply soldering past to the area you will be soldered. You can even put some on every end of the 63 pipes before you assemble them to the manifold pipes.

Soldering is a precision and a patience thing. take your time. It took me about 1 and a half hour, and I'm not a pro. (I'm an electronic automation eng.)

At each apposite end, solder some 1 1/4" fittings to enable you to screw an adapter in order to convert from 1/14 to 3/4" flexible pipe

the other ends will have a welded cap.

Notice that water must come in on one side of the first manifold, and come out on the other side of the second manifold. This will ensure that water will travel the complete distance. (like in commercial heat exchanger)

Step 9: Pressure Test

Before going any further, it would be a good idea to do a pressure leak test.

Connect a water hose to one of the 1 1/4 pipe and a small piece of hose on the other side.
You can mount the 1 1/4 adapter to bring it down to the 3/4.

Turn on the water to flush out the air.

When the air is out, bend the exit hose to stop water from coming out.

Check every soldered joints for leeks. If there are any, completely empty the heater, and retouch.

For those of you unfamiliar with soldering pipes, If there is water inside the pipes, you will not be able to solder them properly.

Redo the test until it's perfect.

Step 10: Cleaning

Clean off all of the solder paste left behind.
Using Acetone, will remove all of it, and really make the metal ready for painting. (make sure it is perfectly dry, acetone and paint is not a good mix for a nice finish)

Step 11: Paint

Use a black mat paint, in spray can or regular. I used both, the spray for the copper, because it's easier to spray paint the small pipes. I used a regular paintbrush for the steel frame to have a thicker quote.

Step 12: Final Assembly

Assemble the 1 1/4" adapter to downsize the pipes to 3/4.

Step 13: Installation

Find a good place were there is maximum sunlight all day. My installation is facing South ( I am in Canada). Anywhere in the southern hemisphere is facing north I assume)

Bolt the water heater on a rooftop or anywhere that is in the sunlight and convenient for you.

Use 3/4 inch plastic tube from the pool filter pump output, to the bottom manifold.
From the top manifold, use a 3/4 inch pipe and go back to the pool.

You can use flexible general purpose, low cost pipes.

You can use 90deg angles to come down from the roof. custom fit the hoses and secure them to the side of the house or whatever it's sitting on.

Step 14: On the Filter and Return

Get a 3 way pool valve. insert this valve between the filter and the pool return pipe.
Add a converter from the pool size pipe, to 3/4" fitting.
Insert the pipe going to the water heater on the 3 way valve.
With this valve, you will be able to regulate the flow of water going into the heater.

Step 15: The Final Result

You probably noticed that I added a glass over the water heater. This is the corrugated type you install over a patio. It's much cheaper then Plexiglas . I pick up a 8'x36" for 19.00$ at home depot.
Plexiglas or acrylic was in the 200.00$

This make no difference in the heat result. It was more because since I live in Canada, I need to protect the fragile 1/4 pipes from bending under the weight of the snow in the winter.

Over all efficiency so far : (tested for 3 weeks from May 17 to June 6 using a calibrated lab mercury thermometer)

Delta T ( temperature difference):
With an outside air temperature of 21C (70F) and the pool water at 17C (63F) the heater turns water from 17C (63F) to 22C (71F) in one day.

Water coming out of the heater is about 3C (1.8F) warmer then the input .

Keep in mind that this data was recorded in the last weeks of May. We are in the spring in Canada (Laval, Quebec) latitude 60 00 longitude 95 00 W

The sun hits the water heater on the roof from 10:00AM to 3:30 PM that's 5.5 hours
Anyone in a warmer and sunnier environment should get much better results.

I just added some black pieces of metal under the 1/4" pipes and blocked off the sides to get more heat. so far it's hard to say it if it make a really big difference.
If I was to make an other one, I would make it twice the size.

Step 16: Swiming 2nd Week of May

For anyone south, swimming in May is probably normal, for Canada, it's exceptional...
Average temperature outside has not gone over 21C ( 68F) and was more in the 17-18C (62-64F)


Pool specification
15' round 52" high
Filter with a 2 speed pump

Location of the heater
It's on a small roof over the balcony, about 18' higher then the pump.
I must use the second speed to start the water from flowing to the heater. Once it primed , I bring it back to the low speed and gravity does it's job.

Have fun , and please make this design even better if you can!

Richard Marier