Solar Pool Heater (DIY)

Seven steps to create a backyard solar water heater for your pool.

My wife and I purchased an above-ground pool for exercise and leisure last year. We observed that in the afternoons, my house casts a shadow over the pool, lowering the water temperature by several degrees in the Spring and Fall. Even though the air temperature was in the 80s, we couldn’t get into the pool until after work on weekdays, which made for some chilly swims. I decided that a solar heater mounted outside the house’s shadow would be ideal for bringing the water temperature down to more manageable levels.

Step 1: The Solar Collector:

I started by painting a 4×4 piece of plywood black. Then I coiled 200 feet of 1/2″ vinyl irrigation hose on the plywood, securing it with UV-resistant zip-ties every foot or so by drilling holes and looping the zip-tie around the hose and through the board. As you can see, 200′ does not entirely cover the plywood; nevertheless, because I followed the square edges rather than using a circular coil, the hose began to kink in the corners. If you look closely at the photo, you’ll notice that I still have a few kinks to iron out.

At around 3:00 PM, I finished up and went outside to take a temperature reading of the board’s surface. The temperature on the surface was around 134 degrees Fahrenheit.

We need to get that beautiful heat into the pool now.

Step 2: Valve Assembly:

Instead of using a separate pump, I put up a set of valves and “Y” adapters to send the water into the heater and then back to the pool, utilizing the natural flow and pressure of the existing pool filter pump. The 1/2″ ball valves allow me to turn off the water to and from the solar heater, as well as remove it after the afternoon temperatures have made it unneeded.

Step 3: Water to the Solar Heater:

The top is a 1 1/2″ “Y” adapter with a 1 1/2 to 1/2″ threaded adapter on one side, a 1/2″ male to male threaded nipple to a 1/2″ ball valve on the other, and a 1/2″ threaded to ribbed adapter on which the vinyl hose glides. To prevent leaks, I installed two hose clamps on each hose fitting. To ensure a good seal, sand all flat surfaces before gluing. IMPORTANT: Threaded pieces should not be glued. Long before you get the threads tight, the glue will have set. Seal the threads with plumber’s grease or pipe dope. Due to the tremendous pressure, even Teflon tape may leak.

Step 4: Regulator Valve:

The middle valve is a smooth 1 1/2″ ball valve that is bonded on both sides to a short piece of 1 1/2″ PVC. The pressure will transfer some water from the top “Y” adapter to the solar heater panel by partially closing this valve.

Step 5: The Return Valve:

The bottom of the assembly is nearly identical to the top. A ribbed to 1/2′ threaded adapter connects to a 1/2′ threaded ball valve, a threaded 1/2″ to 1/2″ nipple, a smooth 1 1/2″ adapter, and a smooth 1 1/2″ “Y.”

The water flowing down the 1 1/2″ PVC pipe and through the 1 1/2″ ball valve will draw water from the solar heater into the pool’s water.

Step 6: Timer:

The hundreds of gallons of cold water in the pool would overrun the solar heater’s 10 or so gallons of water if the water was allowed to flow continuously through it. It wouldn’t have enough time to warm up before being tossed into the pool. To remedy the problem, I connected my pool pump to an outdoor timer. The pump continues to filter the pool for several hours each day, but from Noon until roughly 6:00 PM, a timer switches the pump on and off at 1/2 hour intervals. This allows the solar heater’s water to warm up before being poured into the pool.

Step 7: Hot Water:

The water going into the pool when the heater is on is around 99 degrees F, as you can see. In the shade, this keeps the entire pool at around 84-86 degrees. Everything was purchased for around $50 at Home Depot.

additional option Solar Pool Heater: A Weekend Project

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Mike Hunter

Mike is the owner of the local pool shop. He's been in the business for over 20 years and knows everything there is to know about pools. He's always happy to help his customers with whatever they need, whether it's advice on pool maintenance or choosing the right chemicals. He's also a bit of a pool expert, and is always happy to share his knowledge with anyone who's interested.

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