I can not figure it out. Our pool has developed a very interesting problem. Basically everything seems to be functioning OK, except one skimmer is pulling to much water and empties before it can refill, thus the pump starts to suck air and loses prime. Bizarre.
Some pool make-up: Pentair pumps, filters, and parts. 15,000 gallon pool with a spa. Everything is controlled by a central electronic control system. There are two pumps, one for the normal filter operation, the other for a waterfall effect from the spa into the pool. There is a pool heater, chlorinator, and a filter. I also have a pump for our cleaner ("rover"). Each skimmer has its own valve, along with the main pool drain, separated by a motorized valve that separates the spa main drain. A little diagram below: <> = manual valve. <M> = motorized valve.
The spa part does not seem to be involved, but will explain it just in case. There are two drains on the bottom of the main pool. One goes to the normal filter operations, the other feeds the second pump that pumps directly into the spa to create the waterfall effect from the spa into the pool. There is a valve that extends the spa into the main filtration system or causes the spa to loop back into itself.
The filter has a pressure valve on it and it hovers at 19 or 20, so this is good. When there a loss of prime or the pump is suck area, the pressure in the filter drops and you can see the needle bounce!
All pumps and valves seem to working, so I can not find any obvious equipment faults, but please let me know if I am off base.
So here is the problem:
If the all manual valves are open, drawing water from both skimmers and main pool drain the pump will soon lose prime. Looking at skimmer 2, it will literally have no water in, all be sucked down until the pump loses prime and stops pumping, and only then does it refill with water from the pool.
If I close skimmer #2 valve, the pump will prime again and everything starts working. I have isolated each skimmer, including the main pool drain, and the spa drain (there is a switch on the motorized valve that you can operate to have it turn), and as long as skimmer #2 is off, everything works.
Also note: even with all three valves on, skimmer #2 still empties out and sucks area causing the pump to lose prime. Ugh!
I did some searching online and can not find anything that matches this problem. I watched the video about a possible clog, but that does not make sense since the skimmer basically has too much suction, not too little as a clog my prescribe. I even tried throwing the hose into the skimmer #2 and even with the extra water input, the skimmer empties out and the pump looses prime.
I have checked for leaks in the pipes coming from skimmer #2, but I can not find any.
HELP? Any other troubleshooting I can try?
Some pool make-up: Pentair pumps, filters, and parts. 15,000 gallon pool with a spa. Everything is controlled by a central electronic control system. There are two pumps, one for the normal filter operation, the other for a waterfall effect from the spa into the pool. There is a pool heater, chlorinator, and a filter. I also have a pump for our cleaner ("rover"). Each skimmer has its own valve, along with the main pool drain, separated by a motorized valve that separates the spa main drain. A little diagram below: <> = manual valve. <M> = motorized valve.
Code:
[FONT=courier new]
+-----+-----+-----<M>----+
| | | |
<> <> <> |
| | | |
SKM SKM Main SPA
1 2 Drn Drn
[/FONT]The spa part does not seem to be involved, but will explain it just in case. There are two drains on the bottom of the main pool. One goes to the normal filter operations, the other feeds the second pump that pumps directly into the spa to create the waterfall effect from the spa into the pool. There is a valve that extends the spa into the main filtration system or causes the spa to loop back into itself.
The filter has a pressure valve on it and it hovers at 19 or 20, so this is good. When there a loss of prime or the pump is suck area, the pressure in the filter drops and you can see the needle bounce!
All pumps and valves seem to working, so I can not find any obvious equipment faults, but please let me know if I am off base.
So here is the problem:
If the all manual valves are open, drawing water from both skimmers and main pool drain the pump will soon lose prime. Looking at skimmer 2, it will literally have no water in, all be sucked down until the pump loses prime and stops pumping, and only then does it refill with water from the pool.
If I close skimmer #2 valve, the pump will prime again and everything starts working. I have isolated each skimmer, including the main pool drain, and the spa drain (there is a switch on the motorized valve that you can operate to have it turn), and as long as skimmer #2 is off, everything works.
Also note: even with all three valves on, skimmer #2 still empties out and sucks area causing the pump to lose prime. Ugh!
I did some searching online and can not find anything that matches this problem. I watched the video about a possible clog, but that does not make sense since the skimmer basically has too much suction, not too little as a clog my prescribe. I even tried throwing the hose into the skimmer #2 and even with the extra water input, the skimmer empties out and the pump looses prime.
I have checked for leaks in the pipes coming from skimmer #2, but I can not find any.
HELP? Any other troubleshooting I can try?
...and now the embarrassing part! 
BTW, that is an awfully strong pump for your size pool. If you ever change it out, a 1.5 HP -2 speed or even a 1 hp 2 speed would save you a LOT on electricity and just may pay you back in just a few years.