I wanted to try an experiment with some black 3/4" PVC tubing I had. I spent 1 hour and a total of $5 as I already had the PVC, the tie wraps and the plywood. So here is a quick and easy way to raise your pool a few degrees each day when it's nice and sunny. This instructable is only for creating the solar collector. I will do another one having to do with tying it into your pool system.
TOTAL PARTS LIST
75 - 100 feet of 1/2" or 3/4" PVC tubing
25 - 40 8" tie wraps
25 - 40 1/4" x 1 1/4" wood dowels (optional)
4 x 4 sheet of 1/2" or 3/4" plywood
drill with 1/4" drill bit
cutters for tie wrap
Step 1: Lay Out the Pattern
I used 3/4" tubing so my holes are 1" apart. Find the centre of your back board by drawing a line corner to corner from each side. They will cross in the middle. I started my holes 23" from the centre and drilled to 5" from the middle. Don't try and get any closer then this or your tubing will kink and screw up your water flow. Never do square corners as the kinking and restriction in water flow will defeat the extra tubing you will be able to fit on the board. Also do not put the tubing tight against the next coil as you want the heat to get at all sides of the tubing. More on this later. If you use 1/2" tubing then drill your holes using 3/4" separation.
The test version I made used about 70' of 3/4 inch tubing. There is aprox 52' wound on the board and the rest is to bring the water from the pool to the heater and back. To help you while laying out the tube I used 4 large wood lag bolts that I hand tightened into the 4th hole from the outside in each set of holes. This let me lay down 3 windings and keep them loosely in place while I put my 1st tie wraps through. You can use smaller tie wraps and wrap every winding, I used 8" and wrapped 2 at the same time. Do NOT tighten the tie wraps as you will need to adjust your windings and ensure proper spacing later. If you use individual tie wraps on every winding then you will not need the wooden dowels.
Step 2: Finishing the Solar Collector
Continue laying down the tubing until you have finished your collector. Once all the tubing is on the board adjust the windings so they are all even and not jammed up against each other, sticking up or otherwise messed up. The more evenly they are played out the better for overall heat collection.
The last step in my version is to insert the wooden dowels into the holes between each pair of windings. As I wrapped 2 tubes with 1 tie wrap there is an extra hole available. Hammer the dowel in and the spacing will be perfect. If you use individual tie wraps then you will have no extra holes and no need for the wooden dowels.
Once you are sure that all the tubing is speed perfectly tighten the tie wraps and trim.
To improve on the heat exchange you can add a 1 x 2 frame around the outside of your collector, paint the collector black and drop a 4 x 4 sheet of plexiglass on top. This will dramatically increase the efficiency of your solar heater by trapping the heat inside the box and preventing wind from calling it off.
To test the heater out I just jammed one end of the tubing into one of my pool inlets. I had a spare aluminum barb connector and that was enough to keep it in place. The temperature difference was 2-4 degrees and my pool went up 3 degrees in 1 afternoon. Do NOT run water through your collector once the sun goes down or you will be cooling your pool not heating it. I only run my filtration system for 8 hours each day, I do this from noon to 8 PM.
Step 3: Some Additional Notes and Things to Consider
Do NOT try and put this on top of a 2 story house as most pumps will not be able to drive the water that high without a lot of extra strain and work on the pump. If you have a pool house or shed then these are perfect locations to place a solar heater. Just keep in mind that the heater has some weight to it. Mine is only about 50lbs so no issue. Since this experiment worked very well I will be relocating this temporary heater to my pool house roof and tying it directly into the filtration system. I will post an instructable for that once I get it done. My pool house has brown shingles and heats up light a nuclear over so no need for boxing my solar heater. I will just need to adjust the time of my filtration to start running earlier.
There are several different versions of this that will also work very well. One uses a larger 1 1/2" PVC tube to carry the water to the collector which then splits off into 6 individual 1/2" tubes and then comes back into a 1 1/2" return. This would carry a much larger volume of water and could easily heat up a larger pool. Make sure your pump can handle it before trying this. The six individual 1/2" pipes can be layed out any way you like. Straight along the roof for 20 feet would let them pick up plenty of heat.