Pump Will Not Maintain Its Prime

[Poconos]

Smearing some vaseline on PVC pipe joints (not gaskets) may be a little easier to use than water for finding a leak because it's simply thicker. Wipe it off when done. It won't hurt PVC but isn't recommended for gaskets.
Al

[aylad]

I know this is one of those "no-duh" things, but have you made sure that the water level in the skimmer is sufficient?

Janet

[mas985]

A stuck wier door will also cause problems.

[Poconos]

I missed the intermittent part. That points to what Jan and Mark mentioned and not to an air leak. If the water is low and a vortex is forming in the skimmer and you don't want to add water then put a few small rocks or something in the skimmer basket to break up the flow pattern and you should be OK until the level gets higher. I don't have a weir 'door' but an older style floating circular one that sits in the basket. That has a tendency to stick at high water levels and do the same thing because the flow over the top and into the basket isn't enough to maintain full flow and I would get the same intermittent pumping action.
Al

[kc101]

First thing I did was check all of the above, except blockatge of the main drain. Too cold to get down there w/o a wet suit.

My designated sheer descent pump is a little noisier than the others (same brand & size). Nothing that sounds horrible or something mechanically wrong, it's just more of a lower humming than the other two (especially at start-up), which wasn't the case before the problem occurred.

Thanks for all of the above help and I'll let you know if I find something in the drain.

Merry Christmas & a happy New Year to all.