Solar Panel plumbing question

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piezon50

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Apr 16, 2013
20
Hi,

I will be instaiing my 5 new solar panels this weekend on the roof of my deck (10' above filter level). the questions i have are:
the kit came with 2 check valves but I only thought i needed one valve on the line from the DE filter to the panels to eliminate back-pressure when the pump turns off each day. Do i need to put one on the return line as well?

Also, I'm installing a relief valve that's supposed to allow the panels to drain when the pump turns off but I can't figure out where the water will drain to if the check valve will close not allowing the water to drain below the valve. i was planning on installing the valve on the vertical run halfway up the wall of the house to the roof so there will only be about 5' of pipe between the valve & the bottom of the panels which can't possibly hold the water from one panel, let alone 5 of them.

What am i missing?? thanks
 
Normally you have a check valve where the panel output connects into the return line to prevent water from flowing into the panels when you have them turned off. This allows the panel to drain into the pool.
 
Where the water drains kind of depends on where you put the relief valve.

Some water can drain down the return side through the solar check valve (that John mentioned).
Other water usually drains through the solar 3-way valve. These are often made "leaky" by drilling a small hole in the diverter. I used a Pentair solar valve that has a small check valve built into the diverter (although this only helps for automated systems that turn the solar valve off each night).
 
thank you both. My plumbing is a little different in that i have 2 ball valves that i used with my gas heater as i ddin't want running thru the heater all summer when i wasn't turning the heater on. I recently discarded my old gas heater and am simply continuing the pipes that were runniing in & out of the heater up to the solar panels on the roof, one for the feed & the other for the return. So, I am not using a 3 way diverter. The water will simply flow out of the filter, up to the panels & then back down the return and into the pool. using the ball valves, i can bypass the panels during the heat of the summer as needed. So, with that configuration, do i need a check valve for each pipe (or just one) and should they be closer to the filter or can they be on the horizontal piping leading up to the roof??

Thanks again.
 
You want a check valve right after the filter. Normally you need the one on the solar return before the T back into the main return line, but if you are manually opening/closing both ball valves, then the second one is not needed (it is only needed if there is no valve on the solar return and when the solar is off)
 
OK, now I understand exactly where to put the check valve on the line coming from the filter & feeding the panels. Since my plumbing, with both ball valves open, is just a continuous run from the filter to the panels & then back to the pool, you're saying i don't need a check valve on the return line since that line cannot backwash into the filter as it goes directly to the pool?? Am I interpreting this correctly?
Since the install kit came with 2 check valves, I guess there would be no harm in installing the 2nd one at the bottom of the return line coming down from the roof & unscrewing it to blow out that line for the winter?

Thanks for your input
 
I think a picture of your equipment pad would better help us visualize the setup.

You must also have a ball valve between the solar supply and return lines right? To force the water up to the solar.

You only need a check valve on the solar return if you do NOT have a ball valve that you shut off on the return when the solar is off. It is there to prevent the flow from trying to enter the panels backward when solar is off and the pump is on.
 
You are correct. I have 3 ball valves.
With one open & the other 2 closed, the water comes out of the filter & simply goes right back into the pool as if there was nothing else connected to the system. When I shut that one and open the other 2, the water wasl diverted into my gas heater and then back into the return line and into the pool. The panels are simply replacing the gas heater. The reason for the one check valve now is because the panels will be 10' above the filter vs. the gas heater that was level with the filter. I think I'll just install the 2nd check valve near the bottom of the return line coming down form the roof just to play safe.

Thanks for your help. I'll report back in a week after the install is complete.
 
How many panels do you have? They may not need (or want) all the flow available (depends on your pump size, head loss, and number of panels). So you may need to leave the middle ball valve slightly open.
 
I have five 4x12 panels. 1 1/2 Hp pump, 1 1/2" headers & PVC plumbing. 30,000 gallons, just under 700 sq. ft. of surface.
Not sure what head loss means.

Are you saying that I might not need to divert 100% of the water to the panels so I should experiment by slightly opening the ball valve to let some water go back to the pool directly from the filter if neecessary? What should i be looking for to assess whether or not the system can handle 100% going to the panels?

If I keep that valve partly open, then I will definitely need to install that 2nd check valve.
 

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Determining the head loss (flow resistance) and the flow rate is tricky. Your 5 panels only want around 25 GPM and with a 1.5HP pump, you are likely WAY above that.

I feed my 10 panels with the full flow from my 1HP as a member here (Mark) estimated it should be producing around 50 GPM.

So, you will certainly want to keep the middle valve open a good bit. Although even in this case you will not need the 2nd check valve, but will not hurt.

I would suggest starting with the valve about half open. Then in the full sun when with the pump running after a few minutes, the panels should be cool to the touch. If they still feel warm, then close the middle valve a bit to force more flow through the panels.

Please add your pool details and location as described HERE as it will help us help you.
 
Jason, I noticed in your signature that you have 500 sq. ft. of solar panels for a 20K pool and I just bought 240 sq. ft. of panels for a 30K pool because that's all i could fit on my deck roof. My feeling is that I usually get my pool to 85 in July/August without any panels so having my water run thru 5 4x12's that are in full sun for 8-9 hours per day has to give me much better results plus enhance my temps in June & Sept. as well. Hope i'm not wrong in my thinking process because I now have the panels ready to be installed.
 
Adding any amount of panel area will help. You really won't know how much until you get some run time...your situation may not be the same as Jason's.

Solar panel sizing is more tied to pool surface area than pool volume. I am guessing that yours is ~800 sq. ft. (I assumed an average depth of 5 feet)?

So your panel area will be ~62.5% which is not bad, though if you could get to 100% that would be even better.
 
I certainly do not need the extra heat in the summer ... might use them for cooling though. I found a good deal on 11 used panels on craigslist and was able to fit 10 of them on the roof ... so I put them all up. Mine are more for extending the season. For example, 2 weeks ago my water was over 80 degrees and we were out :swim:

Of course now the weather cooled and is windy and since I do not use a cover the temp is back down around 70.
 
Jason,
I agree that I don't think I NEED the 2nd check valve but, since the system came with 2, is there any harm in installing the 2nd one at the bottom of the vertical return coming down from the roof so i can unscrew it at the end of the season for the water to gravity drain out from the roof and also insert a shop vac into it to blow the water in the rest of the line underground back into the pool? Is there any harm in installing a check valve even though it might not be needed, just in case??
Thnx.
 
Check valves add a little back pressure, one goal in any well designed solar heating system is to minimize the pressure the panels see, this is often done by bypassing some water flow around the panels, using larger eyeball fittings, etc..

Ike
ps, operating pressure depends on the specific panel, but max operating pressure is often between 5 to 10 psi (often panels are tested to much higher levels (80 psi, etc) and allow operating spikes to 30-40 psi) , from this you can see that a check valve that adds as little as 1-2 psi of back pressure is enough to be noticeable.
 
They just add some resistance to the flow, so your pressure will go up and the flow rate will go down a little. I know some members (I may too) have removed the spring to lower head loss ... of course that only really works safely if the valve is horizontal I think.

Interesting idea on using the check valve as a drain, but I am not sure how well the seal will do if you open and close them. It is just as easy to use a T on the bottom of the vertical pipe instead of a 90 and put a hose bib on the bottom.
 
Thanks for all your input & the links.

Jason. I plan on installing a tee with a screw plug on both lines coming off the roof on the horizontal run just after the 90 degree elbow at the bottom of the vertical & will then use another 90 to bring both pipes below ground level before returning to the pool/filter.
I plan on using these tees to drain all the water from the roof at the end of the season (as well as for any period over the summer when I by-pass the panels once the water temp can maintain the desired temp on it's own). I can then use a shop vac thru the unscrewed check valves to blow the water from the underground lines back towards the tees and out the bottom drain plug. Does this make sense??
 

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