New Member - Solar Pool Heating Question

[surfcitybill]

Hello All. New member from Southern Calif. Wondering if any of you solar experts have run across this problem? Any advice would be appreciated.

I've been a pool owner for 12 years and heat the pool with a roof mounted solar panel system. Recently, after the pump has been turned on for about 15 minutes water starts to come out of the roof mounted air vent leaking off the roof. The air vent is designed to allow air back into the system after the pump is turned off so water can drain back into the pool. Seems to me I have too much pressure in the system but I don't understand why since it's worked for years...I've made no changes to any of the equipment except one (I took one 4 x 8 panel out of service that left 13 remaining. This was done last summer). I changed the air vent and that temporarily solved the problem but 2 weeks later it started again.

Even more frustrating is that this happens even when the solar system is completely turned off meaning the diverter valve is set to send the water to the gas heater and by-pass the panels. Could this have anything to do with the diverter valve or other misc check valves? Any thoughts at all? I'm lost.

Thanks,

Bill

[inetdog]

Hello All. New member from Southern Calif. Wondering if any of you solar experts have run across this problem? Any advice would be appreciated.

I've been a pool owner for 12 years and heat the pool with a roof mounted solar panel system. Recently, after the pump has been turned on for about 15 minutes water starts to come out of the roof mounted air vent leaking off the roof. The air vent is designed to allow air back into the system after the pump is turned off so water can drain back into the pool. Seems to me I have too much pressure in the system but I don't understand why since it's worked for years...I've made no changes to any of the equipment except one (I took one 4 x 8 panel out of service that left 13 remaining. This was done last summer). I changed the air vent and that temporarily solved the problem but 2 weeks later it started again.

Even more frustrating is that this happens even when the solar system is completely turned off meaning the diverter valve is set to send the water to the gas heater and by-pass the panels. Could this have anything to do with the diverter valve or other misc check valves? Any thoughts at all? I'm lost.

Thanks,

Bill

Hi Bill and welcome to SolarPanelTalk!

Several things off the top of my head:

1. A bad air inlet valve. But when the second one starts doing the same thing, that goes way down in probability.
2. Excessive pressure. This could be the result of a faulty overpressure relief valve (possibly combined with a check valve for drainback) which is allowing expansion as the water temp goes up to force water out through the valve.
3. If there is an air-filled expansion tank in the system it may have lost its air. As a result any small expansion will cause enough pressure to force open and probably damage the air intake valve. Then the next time cold water comes in past the check valve, the stage is set for another expansion problem. To fix this, drain the system far enough that the tank fills up with air again. If it is an air bladder type tank the bladder has sprung a leak and the tank must be replaced.
4. If there never was an expansion tank, then possibly you have closed a valve somewhere which should have been left open at all times during operation.
5. Something broke.
6. The temperature at the point where the air valve is locate got too high and damaged it.

PS: since water is coming out during normal operation, maybe the most likely problem is that the valve got damaged by temperature or pressure at some point when the system was NOT running and now it leaks even under normal pressures.
Possibly something which happens when you switch the valving to backflush your pool filter and it is a hot day???? Or anything which results in a totally closed roof loop when the diverter valve is set away from the solar heater.

[Naptown]

Hi Bill and welcome to SolarPanelTalk!

Several things off the top of my head:

1. A bad air inlet valve. But when the second one starts doing the same thing, that goes way down in probability.
2. Excessive pressure. This could be the result of a faulty overpressure relief valve (possibly combined with a check valve for drainback) which is allowing expansion as the water temp goes up to force water out through the valve.
3. If there is an air-filled expansion tank in the system it may have lost its air. As a result any small expansion will cause enough pressure to force open and probably damage the air intake valve. Then the next time cold water comes in past the check valve, the stage is set for another expansion problem. To fix this, drain the system far enough that the tank fills up with air again. If it is an air bladder type tank the bladder has sprung a leak and the tank must be replaced.
4. If there never was an expansion tank, then possibly you have closed a valve somewhere which should have been left open at all times during operation.
5. Something broke.
6. The temperature at the point where the air valve is locate got too high and damaged it.

PS: since water is coming out during normal operation, maybe the most likely problem is that the valve got damaged by temperature or pressure at some point when the system was NOT running and now it leaks even under normal pressures.
Possibly something which happens when you switch the valving to backflush your pool filter and it is a hot day???? Or anything which results in a totally closed roof loop when the diverter valve is set away from the solar heater.

Pool systems don't have expansion tanks they are generally open and diverter valves have a bleed hole to allow the system to drain (very slowly) in the event of a valve failure.
Check to make sure you have water returning to the pool when the valve is in the non solar position and when it is in solar.

[surfcitybill]

Hi Bill and welcome to SolarPanelTalk!

Several things off the top of my head:

1. A bad air inlet valve. But when the second one starts doing the same thing, that goes way down in probability.
2. Excessive pressure. This could be the result of a faulty overpressure relief valve (possibly combined with a check valve for drainback) which is allowing expansion as the water temp goes up to force water out through the valve.
3. If there is an air-filled expansion tank in the system it may have lost its air. As a result any small expansion will cause enough pressure to force open and probably damage the air intake valve. Then the next time cold water comes in past the check valve, the stage is set for another expansion problem. To fix this, drain the system far enough that the tank fills up with air again. If it is an air bladder type tank the bladder has sprung a leak and the tank must be replaced.
4. If there never was an expansion tank, then possibly you have closed a valve somewhere which should have been left open at all times during operation.
5. Something broke.
6. The temperature at the point where the air valve is locate got too high and damaged it.

PS: since water is coming out during normal operation, maybe the most likely problem is that the valve got damaged by temperature or pressure at some point when the system was NOT running and now it leaks even under normal pressures.
Possibly something which happens when you switch the valving to backflush your pool filter and it is a hot day???? Or anything which results in a totally closed roof loop when the diverter valve is set away from the solar heater.

Thanks for the input. You bring up some good points. I agree it's not the air inlet valve since the replacement has also failed which I think is a symptom of another problem.

Excessive pressure seems to be the issue but I'm not sure why. There aren't any overpressure relief valves or expansion tanks (as noted by Naptown) in the system. I did check to see that the one return valve was open. Thanks to Naptown mentioning the "bleed" hole in the diverter valve....That would explain why water would still go to the panels even when the diverter valve was set to "solar-off". By the way when I shut everything down, pool pump etc, water definitely drains back to the pool. You can hear it quite easily. And when you first turn the system on a ton of air is forced into the pool as the system fills up.

Inetdog, I think you're right...something broke. Could a malfunctioning check valve really be the culprit. I'm trying to think if I even have one in-line with the system...I have one on the "return" pipe from the gas heater but I don't know why that one being faulty would play a role in this.
How does one troubleshoot a check valve? The "clear" window just shows bubbly water to me.

Your final "PS" is also interesting. The answer might be in there somewhere.

By the way, the reason I'm troubleshooting this myself is because I'm having a difficult time finding someone qualified to do it. Most "pool guys" don't know anything about solar, and many solar guys don't understand pool plumbing.

Thanks again for responding.

Bill

[Naptown]

The check valve should be between the filter and the diverter valve. This is used to prevent the solar from backwashing the filter when the pump shuts down.
there is no need for any other check valves in a typical system and this would be installed before the solar loop and heater.
Lastly and this may seem like a dumb question but is the solar valve installed AFTER the filter or between the pump and filter. Proper placement is between the filter and the aux gas heater.

[Solardude1]

The check valve should be between the filter and the diverter valve. This is used to prevent the solar from backwashing the filter when the pump shuts down.
there is no need for any other check valves in a typical system and this would be installed before the solar loop and heater.
Lastly and this may seem like a dumb question but is the solar valve installed AFTER the filter or between the pump and filter. Proper placement is between the filter and the aux gas heater.

Hi Bill,

I'm with the largest manufacturer of solar pool heating systems in the US. At first thought, what you're describing sounds more like a lack of pressure (flow) through the solar array. This could be related to a number of things like a dirty filter, the filter pump not performing to spec or the system diverter valve not in it's proper position, reducing flow to the solar array. I would be happy to recommend one of our Master Dealers in your area. They are experienced with all leading brands of solar pool heaters in the market.