Last year my Wife and I bought an above ground pool for exercise and recreation. We discovered that my Home shadows the pool in the afternoon, and that drives the water temperature down several degrees in the Spring and Fall. Since we usually don't get into the pool on Weekdays until after work, this made for some pretty chilly swims, even when the air temperature was in the 80's. I decided that a Solar heater that I could mount outside the shadow of the house would be just the thing to bring the water temperature up to more bearable levels.
Step 1: The Solar Collector:
I took a 4x4 piece of plywood and painted it black. Then I took 200' of 1/2" vinyl irrigation hose and coiled it tightly on the plywood, using UV-resistant zip-ties to secure the hose every foot or so by drilling holes and looping the zip-tie around the hose and through the plywood. As you can see 200' doesn't completely cover the plywood, but since I was following the square edges instead of using a circular coil I ran into a problem where the hose started to kink in the corners. If you look closely at the picture you can see I still have a few kinks to literally work out.
All done, and in the Sun, I took a temperature reading of the surface of the board at about 3:00 PM. The surface read about 134 degrees F.
Now we've got to get that lovely heat into the pool.
Step 2: Valve Assembly:
I put together a series of valves and "Y" adapters to route the water into the heater and then back to the pool, using the natural flow and pressure of the existing pool filter pump, instead of a separate pump. The 1/2" ball valves allow me to shut off the water to and from the solar heater and remove it once the afternoon temperatures make it unnecessary.
Step 3: Water to the Solar Heater:
The top is a smooth 1 1/2" "Y" adapter with a 1 1/2 to 1/2" threaded adapter in one side with a 1/2" male to male threaded nipple to a 1/2" ball valve and a 1/2" threaded to ribbed adapter that the vinyl hose slides on. I used two hose clamps on each hose fitting to avoid leaks. Sand all smooth surfaces prior to gluing to assure a good seal. IMPORTANT: Do NOT glue any threaded parts. The glue will set long before you get the threads tight. Use Plumbers Grease or Pipe Dope to seal the threads. Even Teflon tape may leak due to the high pressure.
Step 4: Regulator Valve:
The middle valve is a smooth 1 1/2" ball valve glued to a short piece of 1 1/2" PVC on both sides. By partially closing this valve the pressure will divert some water out of the top "Y" adapter to the solar heater panel.
Step 5: The Return Valve:
The bottom of the assembly is pretty much a mirror image of the top. A ribbed to 1/2' threaded adapter to a 1/2' threaded ball valve, to a threaded 1/2" to 1/2" nipple, to a 1 1/2" smooth adapter, to a smooth 1 1/2" "Y".
The flow of the water down the 1 1/2" PVC pipe through the 1 1/2" ball valve will draw the water from the solar heater into the water that flows into the pool.
Step 6: Timer:
If the water were allowed to constantly flow through the solar heater, the hundreds of gallons of cold water in the pool would overwhelm the 10 or so gallons of water in the solar heater. It simply wouldn't have enough time to heat up before it got sent to the pool. To solve this I installed an outdoor timer to my pool pump. The pump still runs several hours a day to filter the pool, but from Noon until about 6:00 PM the timer turns the pump on and off at 1/2 hour intervals. This gives the water in the solar heater time to heat up before it goes into the pool.
Step 7: Hot Water:
As you can see, the water flowing into the pool when the heater is operating is about 99 degrees F. This keeps the entire pool at about 84-86 degrees in the shade. Everything was purchased at Home Depot and cost about $50.
Now my Wife and I can get into the pool with an "Ahhhhh" instead of an "OOOOOOoooo".