Replies

1. GBA Editor
   Martin Holladay | Aug 12, 2015 08:45am | #1

   Richard,
   I'm not an expert at solar systems for swimming pools, but I have a copy of an excellent book by Tom Lane called Solar Hot Water Systems, 1977 to Today: Lessons Learned. (You might want to buy a copy of the book.)

   In most systems (if I understand correctly), the same pump that is used to circulate water through your pool filter is also used to circulate water through your solar collectors. You will probably need a control called an automatic solar pool control.

   Lane writes, "A 1-HP pool pump can easily circulate the water through solar pool panels. ... You want 90 to 95% of all the water the pool pump is filtering to go through the collectors as fast as the flow through the filter. Most pool pumps have enough static head to lift water 60 feet straight up. The returning water will form a syphon on the way back. The water in the collectors drains back into the pool through the return jets when the pump turns off. There is a 2-inch, 1/2-psi check valve after the filter to prevent backflow through the filter when the pumps cuts off and water drains back from the roof. A normally closed vacuum breaker at the end of the collector bank on the roof opens to let air into the collectors. The weight of water falling back into the pool pulls the vacuum breaker open."

   There is lots more good information in Lane's book, so buy it.

2. 
   charlie_sullivan | Aug 12, 2015 10:09am | #2

   Solar heating of pools is a nice opportunity to use low-cost unglazed solar collectors. They are less efficient, but given that you aren't heating the pool as hot as domestic hot water, and you aren't interested in doing it when it's cold outside, the efficiency difference isn't very big, and the cost difference can be big. One such product: http://fafco.com/sph/default.aspx

3. 
   charlie_sullivan | Aug 12, 2015 10:11am | #3

   I meant to also say--thermal siphoning can only work to bring hot water up to a higher location. If you can put the pool on the roof and the solar collectors on the ground, that might work, but the payback time for moving your pool to the roof would be prohibitive.

4. 
   StutsFX | Aug 12, 2015 12:28pm | #4

   That makes sense- the cooler water needs to have the warmer water below it. Now, if I COULD put the pool on the roof.... If I do use the existing pump it involves tearing into concrete and plumbing 120 ft. of pipe, round trip. Between internal friction and heat loss that could be a deal breaker. Or, add a second electric pump- expensive in the long run. Would that pump need to be a full size pool pump also???

5. GBA Editor
   Martin Holladay | Aug 12, 2015 12:34pm | #5

   Richard,
   I suggest that you call up an experienced solar thermal system installer. Trying to learn a new trade, one step at a time, over the internet isn't a good way to install new mechanical equipment.