I'm a new pool owner, as of about May 2015. I'm fairly confident we have a suction side leak, but I don't really have a basis for how much air getting into the system is "OK" (if any), and would love some guidance on what to try from here. I've made a couple videos to demonstrate what's going on.
The pump is a 2HP variable speed pump, and it (along with the filter and other equipment) sits approximately 4-5ft above the pool surface, and about 30-40 feet away. There is also a solar system with a check valve on the return, which has been winterized (blown out with air). (The rest of the system has been left running over the winter, since the weather here is mild, only occasionally dipping below freezing.)
Since the pool was first opened we've been having problems with air getting into the system whenever the pump is shut off for more than a few minutes. Our pool contractor has re-sealed several joints, added a check valve before the pump (on the suction side) and most recently replaced the pump housing. These have improved the situation, allowing the pump to be off for longer without the water completely draining out. However, if it is left for a few hours, most of the water will still drain back into the pool if left off for any period of time. Also, if I bleed the air out of the filter pressure valve, even just a few minutes later there is a significant amount of air built up to bleed out again.
Looking at the pump basket or the check valve before the pump, I can see a continuous stream of bubbles flowing with the water. (There are also continuous bubbles in the pool returns.) What I have noticed most recently is that there are considerably more bubbles coming from the drain line than from the skimmer. This video demonstrates: Suction side leak - YouTube
Also, when I shut the pump off, I can hear bubbles coming up from the drain line. So my understanding is that either the leak is in the first part of the L joint, right after that pipe comes out of the floor into the equipment shed there, or that it's underground somewhere. (I'm hoping the former, obviously.) However, I can't hear any air being sucked in there. With past leaks I've been able to hear it hissing in. I can't really do the trick of pouring water over it as it runs, because it would flood the shed.
So one question is, how likely is it that it's underground? I would think that even if a pipe was leaking underground, there would only be so much air for it to pull in, since it would be surrounded by dirt.. but maybe I'm totally wrong there. Regardless, I guess the first thing to rule out would be the joints up to the suction side valve here. Is there a way to test them without flooding the shed?
Also, after taking that video, I've noticed that even if I have that valve set all the way to the skimmer side, there are still some bubbles flowing in, just not nearly as much. This, for instance, is with the valve all the way to the skimmer side (drain line completely shut off): Skimmer air - YouTube
It seems intermittent though, for some reason. Also it's not as bad if I turn the pump speed down. Still, even with the drain line shut off, after running for a few minutes, I can bleed a bunch of new air out of the filter. The top of the pump basket slowly fills up with air too. So.. is that normal? Or would it be considered a problem too, even without the larger amount of air coming from the drain side?
Finally, while doing this troubleshooting, I noticed a strange rattling coming from the valve, only at certain positions: Valve sound - YouTube Sounds like maybe something got pulled in and is now stuck in or next to the valve? Should we open it up?
One last thing. Whenever the pump is shut off, a large stream of bubbles is sucked out of the check valve on the way back from the solar. That makes sense since it's full of air, and when the pump is shut off there will be a vacuum on the pressure side of the system (especially since everything is a few feet above the pool). What's odd to me though is that this happens every time the pump is shut off, and has all winter. Theoretically the solar system should all be sealed, so even if some air could be sucked out, you would think eventually it would be at a bit of a vacuum, so it wouldn't be possible to keep sucking more out. So I'm thinking what must be happening is that while the pump is running throughout the day, a small amount of water is leaking back through the check valve into the pipe that runs from the solar. Then when the pump shuts off at night, air is sucked back the other way. Either that or there's yet another leak in the solar that's letting air get in there as well. What do you think, and is it worth worrying about? I don't think it's related to the problems mentioned above, since this is on the pressure side, and the air definitely seems to be entering on the suction side, but I'm wondering if it's another issue. Our pool contractor says if we want he could add a manual valve after the check valve, for winterization.
Thanks in advance for any advice!