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passive solar heater

Here's an easy to build passive solar pool heater that really gets the job done. My father built one of these and installed it all in one day. You can make it as large as you want but remember that it will be installed next to your pool so you don't want to get too carried away. You can install it laying flat or upright and you can design your own configurations. All you need for it to work is full day exposure to the sun.

You'll want to have the passive collector placed on a hard surface which is painted flat black to get maximum value from the sun. A simple wood platform about 12 inches off the ground works great, or a concrete pad can make the project look especially professional. In areas where there is a high concentration of swimming pools an industrious person can even keep pretty busy building and installing these passive heaters for client pool owners. Additionally, similar solar collectors are being used to preheat water for in home use but that requires special engineering and a consultation with local building inspectors.

Build your solar collector using standard black PVC pipe of a diameter the same as or slightly larger than your pools own water lines. If you can't get black PVC pipe in your area, you can use the lighter colored types by lightly sanding them and then applying a coat of flat black spray paint. Your collector must be installed on the discharge side of your filter because sending heated water into your filter will compromise the filters own operating temperature as well as create an increased potential for breeding dangerous bacteria. Let the glue joints of your newly built solar collector cure for 24 hours before putting the pool filter system back into service. You may also want to consider using flexible, hose clamp connections at the intake and outflow ends for easy draining of your solar collector at the end of the swimming season.

  • sue

    HOW HOW HOW do you hook it into your water lines? I understand you have to put it after the filter and chlorine machines, but what kind of connections etc of stuff do I need. I need diy step by step. I can't find this info anywhere, please help.

  • Brian

    You could also wrap your lines up in a trough collector made from 6" pvc cut down the center (u shaped) and apply reflective mirrored film..
    put end caps, drill a hole in the center of the end cap
    push the pipe through and it it is then suspended.... using the mirror as a 95% collector...

  • Mo Lubee

    As a well and irrigation contractor, I would suggest their may be enhanced circulation performance gained by building the solar panels using large tubing coming from the pump and exiting to the pool, then using smaller CPVC pipes painted black and mounted vertically (manifolded) in a roof-mounted panel box. This will cause the heating process to contribute to the circulation, by causing the heated water to be forced upward (heat rises) and out, rather than being forced up and down through a coil.

    Also, pool pumps are not designed to handle back pressure, you might look into selecting a continuous duty sprinkler pump for circulation purposes. The sprinkler pump would react better to the back pressure being generated by friction loss transport to the roof. The roof lift alone will produce 5-8 lbs psi (plus friction loss) back pressure on the pump.

  • Bob

    I struggled with many different solutions to heating up the pool. I live in Northern Ontario, Canada where we have a pretty short season. We have an 18' x 4' easy set pool which holds about 40,000 litres of water. Yesterday morning the water temperature was at 64 degrees, by mid-afternoon it was 72 degress. The secret to heating it up so quickly lies in not taking the water out of the pool. It is true that you want as much surface area as possible to get solar gain, but you don't need to pump the water out of the pool to heat it.

    All you need to do is go down to the home center and pick up a few sheets of 4' x 8' black coroplast. Sink them to the bottom of the pool. I weighed mine down with a few bricks. That's it. Wait for it to warm up. If it's a sunny day, it won't take long. Then pull out the coroplast and bricks and enjoy.

    I know it's not nearly as much fun as playing with plumbing fittings and checking for leaks everywhere, but it does work.

  • Michael

    How does a couple big sheets of black pastic heat up the pool. Coroplast is plastic, correct?

    Let me know I would be very interested in trying this.

  • Bob

    Yes, coroplast is plastic. It's used alot in the sign industry, so if you can't find it at the home center, you could try calling a sign shop.

    Black absorbs more solar energy than lighter colours. As the coroplast absorbs the solar energy, it heats up, and in turn heats up the water molecules in contact with it. The heated water molecules rise and are replaced with cooler water molecules, which are in turn heated, etc. etc.

    If you place your hand on the surface of the submerged coroplast, it won't feel hot like the hood of a black car in the sun, but that is due to the fact that water is an excellent conductor of heat energy and the solar energy is transferred from the coroplast to the water on an ongoing basis. In comparison, air is not so good a conductor of heat energy which explains the hood of the car being so hot.

  • Adam

    I had a couple of questions...
    What is the highest temp that you have seen using your method of Coroplast at the bottom of your pool?

    Is there any chance that the edges of the plastic sheet can damage the pool liner?

    Do you still use this method?

    If so, have you made any modifications to what/how you are doing it?

  • Adam

    how big do I need it to be effective for an 18,000 gal inground pool?

  • Frank Hartman

    I have a 24' round above ground pool approx. 12,000 gals.. My question is how long should I build
    this, and how high.
    Thank you

  • Dakota

    As one who's worked with quite a bit of PVC and on quite a few plumbing projects I'd suggest considering doing this a bit differently instead.

    First, your design show wastes much surface space, there are huge gaps in it that let sunshine go to waste.

    Second, PVC fittings are costly and you have waaaay too many of them.

    Here is a better idea.

    Materials Needed:
    - A long spool of large diameter flexible hose that is close to the same inside diameter as your existing water lines and is UV resistant,
    - Hose clamps as needed,
    - flat black spray paint as needed,
    - 4x4 or 4x6 sheet of plywood -OR- two 2x6's pieces screwed together to form a "X"
    - Large bag of zipties or soft wire,
    - Misc tools: hammer, screwgun, pliers, wirecutter, etc....

    Take the hose and starting about 16 to 24 inchs out from the center of the plywood or from the center of the 2x4 "X" form a flat spiral with the hose. Basically you want to start far enough out from the center so that when you bend the hose it does not kink and pinch off the flow of the water.

    As you wind the hose around and form the spiral you can use the wire or zipties to attach the hose to the wooden "X". Be sure you keep the hose layers close to the last as you wind that way there are no gaps for the sunlight to pass through.

    When you have your spiral as big as you want/need you just have to double check your wires and zipties and hook it into your original water lines.

    Another idea is to cut some flat pieces of styrofoam to fit behind the hose to minimize the heat loss from the back side (unlit side) of the spiral.



  • Gary E. Sattler

    Thanks for your excellent input Dakota! Your construction sounds much more efficient than mine. I never stopped to think that you can buy PVC in bulk rolls.

    Thanks again!


  • Gary

    Rolls of black polyethylene the hardwares sell work well. No fittings to contend with, just spread the coils out.

    A couple more homemade solar pool heater here:
    The one based on aluminum soffit material has 100% effective area -- you don't lose the space between the pipes.

  • 12 Comments / 1 Pages

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