How far can my solar panels be from the pool?

dhulls

Active member
Sep 13, 2010
33
Lesotho, Africa
Hello, I just moved to a new place that has a pool. The pool is about 125 feet from the nearest roof. Is this to far to run my pool water to heat? I don't know the pump size, as the label is covered. I plan on trying to remove some covers to have a look next weekend. The pool is aprox. 18,000 Gallons. Thanks
 

mas985

TFP Expert
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May 3, 2007
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Pleasanton, CA
With 250' of pipe round trip you might want to use at least 2.5" pipe. Also, put in a bypass valve so not all of the flow rate needs to go through the panels. What size panels are you planning on?
 

chem geek

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Mar 28, 2007
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San Rafael, CA USA
Welcome to TFP! :wave:

You could even go with 3" pipe. The price of 2.5" and 3" is fairly close ($2.12/foot for 2.5"; $2.29/foot for 3") and 3" would provide even lower resistance to flow.

I have 12 panels for my 16,000 gallon pool so if you use something similar with 4 GPM flow rate through each panel, then at 50 GPM the following is the head loss for 250 feet of pipe based on this chart.

50 GPM, 250 feet, 2" pipe: 250*(4.3/100) 10.8 feet of head (4.7 PSI)
50 GPM, 250 feet, 2.5" pipe: 250*(1.8/100) 4.5 feet of head (1.9 PSI)
50 GPM, 250 feet, 3" pipe: 250*(0.6/100) 1.5 feet of head (0.65 PSI)

If you have more panels or otherwise use a higher flow rate, the savings from the larger pipe diameters are even greater.
 

dhulls

Active member
Sep 13, 2010
33
Lesotho, Africa
Thanks for the info. I am actually based in a small country of Lesotho (Southern Africa) where we have lived here for 5 years. I will have to see what pipe I can get locally. The panels are 1.2 x 3 Meters so about 4 x 9 feet, and will probably start off with 8 panels, and add more next year.
 

chem geek

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Mar 28, 2007
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San Rafael, CA USA
If you were unable to get 2.5" or 3" pipe, you could just do double-runs of 2" pipe in parallel since that would split the flow rate in half through each pipe so in my example above this would be 25 GPM in each 2" pipe for a head loss of 250*(1.25/100) = 3.1 feet (1.4 PSI) so better than a single 2.5" pipe (there would be some losses teeing the pipes together at each end, but not very much (equivalent to adding 25 feet or so to the pipe run).
 

mas985

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With only 288 sq-ft of panels, you could probably get away with about 25 GPM to the panels so even though 2.5" pipe would be better, 2" should be good enough. You would lose only about 1 PSI. If you add a lot more panels next year, then you might want to run a second 2" line.
 

duraleigh

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Sort of a side note, but I would guess the heat gain from the panels would be partially negated as the water traveled back and forth (I assume underground) to the pool.

At some combination of dwell time, temp differential, ground temp, etc., a very long run to and from a solar collector would not be worth it.
 

mas985

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Good point Dave. Also, the panels do not need to be installed on a roof so I would be curious to know why the panels could not be put closer to the equipment even if they are on the ground. It sounds like the OP lives on a fairly good chunk of the land if the pool is 125' away from the nearest roof.
 

dhulls

Active member
Sep 13, 2010
33
Lesotho, Africa
Thanks for the help guys. The property our house is on is really long and skinny. There are a few places lower than the pool I can put a couple groups of panels. (nowhere to put one long run of panels) I understand pressure when placing panels on a roof, but what do I need to look at if I place my panels at pool level or below pool level. Any concerns there?
 

duraleigh

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In a closed system, (no air in the system) the water can pretty easily be pushed up to the panels as the water descending back from the panels equalizes the pressure. The same will be true if the panels are downhill from the pump but there's a caveat....

You will need to allow for drainage from the panels when the pump is off. Mas985 can probably help you decide how best to accomplish that but keep in mind that that long run is probably gonna mess with the effectiveness.....perhaps enough to make it not worth doing unless you installed insulated pipes to and from.
 

mas985

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May 3, 2007
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Pleasanton, CA
The only concern with putting your panels at pool level or below is that they will not be self draining. If you get freezing weather at all this could be a problem but then you could simply drain the panels manually with a valve on a low point. Another option would be to build a rack for the panels such as this example.
 

dhulls

Active member
Sep 13, 2010
33
Lesotho, Africa
i think I will build a rack like you showed and plan on draining the panels manually. Do I need to drain it daily or just when I shut down the pool for the winter? Thanks again for all the help
 

mas985

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May 3, 2007
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Pleasanton, CA
Winter is certainly a concern about water freezing in the panels. However, if you put the panels on an elevated rack, you could then use a vacuum release valve in the upper portion of the panels so that they will be self draining. The valve is not that expensive and it will save time and effort plus you won't have to worry about draining the panels.
 

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