Help! Left on vacation and once back pump won't prime and Guests coming over

I left for surgery and had my sister come over and take care of my kids and the pool while I was out. They apparently used the pool and water features w/o problem during part of the time I was gone. When I get back the first thing I do before even hobbling into the house is check the pump. The pump is running but no prime and basically little if any water in the pot. Shut it down, do everything I normally do to prime pump (only needed at start of season) and it still won't prime.

Pump is a Pentair challenger 2hp and is 2 1/2 years old. I have 4 inlet lines and have tried each separately and together without luck. Bought a 'Drain King' unclogger piece that fits on your garden hose and blew out one line and can get water thru it, although with being on a well there is not much pressure, still more than enough to fill the pot. Probably would not be enough to sustain the pump however so havent tried that as a direct feed method.

My guess is pump probably ran for a at least a couple of 8 hour periods without prime. What can I do?

When you fill the pump basket and fire the pump does it drain the basket quickly as it normally would do? That would indicate the impeller is OK and it is pumping. If it does pump then the next thought is an air leak somewhere on the suction side. Any sign of overheating on the basket lid or pipe fittings at the pump? Normally overheating of the basket area would occur when the output is blocked and you're just churning water in the basket and getting the water hot. That could warp things. Really sounds like an air leak though and it could be a hairline crack somewhere. Doesn't take much of a leak to prevent priming. Did your sister have to open the basket lid for any reason while you were gone? Look at the basket lid first then valves and finally the piping and bonded joints. You really won't know until you get it pumping at pressure if the seal has been damaged by running dry for those time periods.
Best I can do for now and wishes for a speedy recovery.
Al

When you fill the pump basket and fire the pump does it drain the basket quickly as it normally would do?

Yes, it seems pretty much the same in that regard.

Any sign of overheating on the basket lid or pipe fittings at the pump?

Don't think so but I really don't know what this would look like.

Normally overheating of the basket area would occur when the output is blocked and you're just churning water in the basket and getting the water hot.

This could well have happened not because of blockage necessarily but because of starved for water.

Did your sister have to open the basket lid for any reason while you were gone? Look at the basket lid first then valves and finally the piping and bonded joints.

Really doubt it but I'll check that seal again.

Thanks for the help and followup response to my responses are Always appreciated.

Mike

Hi Mike,
the heating of the basket would occur when water is in it and not moving, not when dry. What happens is when the output is blocked and water isn't moving, a lot of the energy the motor puts out is transferred to the water by the impeller. Basically the old lab experiment where you stir a container of water vigorously and measure the temperature rise to determine how much energy you put into the water. With the power a pump motor can put out you can actually boil the water and regular PVC starts softening a little before boiling temps. Thus the integrity of any threaded PVC joints into the pump housing can be compromised. You can use vaseline to check for leaks at the joints. A lot cheaper than silicone grease and as long as you wipe it off and remove the last traces with an alcohol soaked paper towel you'll be ok. I don't think vaseline should bother the materials anyhow but leaving a residue will collect dirt. Don't use it on O-rings and seals though, like the basket lid seal. Use silicone grease.
Since you have ruled out blockages I believe, the way it happened it sure sounds like an air leak. Just a matter of finding it. One more thing to try to get some idea if the pump seal is OK is to take off the basket lid and using a 5 gallon bucket pour water into the basket and let the pump circulate it. Maybe a couple garden hoses instead to provide enough water to build up some pressure. If you see any dribbles coming from areas that are normally dry then that could give a clue.
Al

You can use vaseline to check for leaks at the joints.

How do you use Vaseline to check for leaks? I'm sure the answer will be obvious and I will look dumb, but I've just never heard anything about this...

Merci beaucoup!

Vaseline is thick and forms a pretty good seal for checking suction leaks. Unless the leak is large the vaseline won't get sucked in as would water or something thinner.
Al