Pump Will Not Maintain Its Prime

I have a Whisperflo 2HP pump for my Sheer Descent waterfall. It has been operating flawlessly for two years. It recently started losing its prime and the pump pot would intermittently fill and partially empty with water, causing an inconsistent flow to the waterfall. I’ve inspected the lid, lid gasket and piping for cracks and all seems ok. I’ve attempted to feel for debris in the impeller but can’t reach that far into the pump.
After re-filling the pump w/ water and re-starting, it appears to operate fine for a few minutes and then the inconsistent emptying and filling of the pump pot starts again. The pump never stops pumping, but continues to pump intermittently.

Welcome to the forum!

From where does the water feed the pump? I suspect a dedicated main drain, check to see that it's not obstructed.

An air leak on the suction side would also cause this, try dribbling water on the lid, influent port and any valves, unions or fittings you can see above ground. If the air in the pump housing lessens when water is poured on a certain area, that's an air leak and we'll help you address it:)

Thanks Ted, I'll check those out.

Not to thread jack... but I was wanting to post the exact same topic and am looking for more insight into this problem.

My pools main pump is losing its prime. It was a problem I had a few months ago when first starting the pool up (my first year with the pool/house). But in the last month of two it has held pretty consistently until yesterday. The pump lost its prime almost as soon as it fired up and I caught it pretty fast. Re-primed pretty easily and it ran fine the rest of the night.

I came home today, the pump had been running about 2.5 hrs, and at some point it lost its prime again. The water was steaming hot and the basket was empty... Is there an ideal adjustment on the valves to avoid this problem? I have a skimmer, cleaner, and drain line for inputs. Waterfall and jets as outputs...

I guess I'm totally thread jacking here, I apologize. I can repost a new topic if that would be better..

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

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

A stuck wier door will also cause problems.

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

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.