Pump pot partially drains after shut-off

[AnnaK]

I'm not really sure what's going on here.

The pump runs during the night and shuts off at 06:00. I'm generally up by the pool around 10:00 to clean the skimmer and PoolSkim and see that the pump pot is 1/2 empty. It used to be that the pot was filled to the very top of its domed lid with an air bubble the size of a quarter.

There is no evidence at all of any water leak anywhere. All the plumbing and the ground beneath it is bone dry.

What can I check or do to determine why the pump pot is losing water?

[Watermom]

This is certainly not my department -- dealing with pumps, but to me it sounds like a suction side leak. I'll ask Al to take a look at your problem and give you his 2 cents.

[Poconos]

I'm a little puzzled. The problem you describe is typical of a pump located above the waterline as with an inground pool. Is you pump above the waterline? Let's assume it is and further assume both the pump and filter are above the waterline. My first guess would be the pump basket lid and since that is on the suction side you wouldn't see any dribble and the leak may be so small you see no bubbles when the pump is running. My second guess would be the multiport valve. Gaskets sometimes do funny things. Seal under pressure and leak under vacuum, i.e. when the pump is off. Could be sucking a little air via the waste port. Any way to put a cap on that pipe and seal it to verify? Now, if your equipment is on the ground below the water level of the pool.....I don't understand something and you can ignore what I said above.
Al

[waste]

Hi Anna and Lisa. :)

Sounds like a small return side leak (after the pump), just enough to break the vacuum. Check under the pump for a little water after the pool has been running for a few hours. Also check the backwash line for a drip as well as the filter base for water.

[AnnaK]

Al, the pump is well below the water line. It's probably even below the bottom of the pool. This is a new issue that we haven't experienced in our previous 5 seasons.

Ted, I can try to seal the waste line. I may have some expansion plugs in the tool box.

One thing I did notice, moisture inside the gauge. We had taken it off for winter and stored it inside. After installing it again this year it got damp inside. I bought a new one and we put it on, and it got moisture in it as well. So, there's something not quite right here. Is that enough of vacuum break to cause the pump pot to drain down?

There is no water under the pump, on any of the pipes and fittings, anywhere near the filter. The only visible oddity is the moisture in the new gauge. The multiport seal, again???? My filter, alas, is the ONLY Hayward model for which you can't buy just a gasket; you have to get a whole new head.

[Poconos]

OK, something I just don't understand. How can water drain out of a pump when it's below the pool water level? Are there ANY components, hoses etc, that are above the waterline? Air gets into a system by negative pressure. With everything below the waterline there should be no part of the system under a negative pressure. If everything is below the waterline then opening any part of the system will let water out, not air in.
Al

[AnnaK]

I don't understand it either, Al. No part of the system is above the water line.

When I checked the skimmer sock that day It was full of bracts and soggy pollen. Is it possible that it was so clogged that not enough water went through the skimmer into the pump? I've kept an eye on it these past 2 days and have changed skimmer socks twice daily, and the issue seems to have resolved itself. The pot is filled completely and has its normal small bubble directly in the center of the domed lid. I can't help but think the pump was starved for water when the sock was dirty.

[mas985]

I can't help but think the pump was starved for water when the sock was dirty.

When the sock is dirty it will create higher suction at the pump which in turn can draw air into the lines from small leaks. By morning, a lot of air can remain in the pump basket because there is not enough flow rate, due to the higher head loss of the dirty sock, to remove the air.

[AnnaK]

Thanks Mark. Looks like that's what may have been going on.

[Poconos]

I kind of figured there was more going on but never thought along the plugged suction path. Glad the problem resolved itself.
Al