Pump losing prime in 'cool' weather

[sammm]

This is a weird one. The past few days we have had fairly warm weather during the day and night. The other morning it was cool (40's) and cloudy. When the pump timer kicked on at 9am it would not prime. I turned it off and planned on looking at it after work.

After work I cleaned everything up, lubed the O-ring on the strainer basket and the big O-ring around the filter itself where the lid sits. (I have a Pentair NSP60 filter - all stainless steel with an O-ring and 'clamp' around the filter and lid) It was around 70 degrees in the afternoon and when I turned the pump back on it primed and ran fine.

This morning when it was in the 40's again, same thing...would not prime. Turned it off and then back on this afternoon (around 70 degrees) and it magically works again.

I'm guessing something is contracting when it's cool and that's what is causing my air leak. When things warm up, it expands and no more leak, or at least not bad enough to lose prime. I've replaced the O-ring on the strainer basket and ordered the big O-ring for the filter lid today. Any other ideas?

 

[spishex]

If you've got a multiport on your filter, I'd try running it during your problem hours on recirculate just to see if it's really a suction side problem. If it really is weather related and not just coincidental the first thing I would check is the DE since that might get a little harder to push through as it got colder. Did you clean and recharge your grids when you took it apart?

 

[sammm]

I'm not sure what a multiport is. Would you please explain?

I didn't recharge the DE the other day, but did so a 2-3 months ago after the swim season was over. The filter runs 4 hours a day (2-hours, 2x a day) during the winter.

 

[spishex]

Do you have any sort of valve between the pump and filter that allows you to backwash the DE? Sometimes there's a rotary valve with six positions like backwash, waste, rinse, filter (that's a multiport), others have a plunger style valve just for backwashing called a push-pull valve, and others are just plumbed straight in.

 

[sammm]

Thanks for the explanation. I only have a push-pull valve for backwashing.

EDIT- High 50's this morning at 9am when the filter kicked on. Pump primed and ran with no problems.

 

[sammm]

So much for the temperature theory. Yesterday evening when the pump kicked on at 6pm, temp near 70 degrees, it would not prime. It had run fine for days and then all of a sudden it won't prime again.

I'm going to cave and call a pool service company. Anyone in DFW have a recommendation?

 

[spishex]

Sounds like you've just got air entering the system overnight. If you give the whole set up a once over, lubricate your o-rings, seal your plugs, etc. I bet you'll be able to find the culprit. Did either the tank or lid o-rings leave your hands black after you lubed them before?

You might also check the impeller for debris just to be sure it's running at full power.

 

[mas985]

If everything is working properly, the pump should not lose prime over night. As spishex pointed out, air is entering the plumbing somewhere where it shouldn't.

Do you have a solar system? If not then it could just be a bad seal on the pump basket lid or a leaky valve on the suction side.

The poor priming performance could be due to a clogged impeller. After the pump is primed and running, what is the filter pressure? Is that lower than normal?

 

[sammm]

No solar system. I cleaned and re-lubed the pump basket lid o-ring again yesterday and it still would not prime. I did get my new o-ring for my filter yesterday, but didn't get a chance to install it.

I haven't inspected the impeller yet, but will do that ASAP. Once it's primed and running, pressure is normal. (~18 PSI. It's around 14-16 PSI after a thorough filter cleaning).

There is a 3-way Jandy valve on the suction side that I haven't even considered. I'll take the top off of that too and inspect it.

To top it all off, it primed and ran this morning.

 

[sammm]

I don't want to jinx it, but I think the mystery is solved. I took apart everything that we had discussed to inspect and lube. I found a small 2-3" square piece of heavy blue vinyl (I don't have a vinyl liner) inside the 3-way Jandy valve on the suction side. It looks like it was partially clogging the inlet valve to the strainer basket. It was probably moving around with the water flow and was clogging the line off and on. I have no clue where it came from or how it made its way into the valve.

Thanks to everyone for the help and suggestions!