New variable speed pump loosing prime at low speed

I finally bought a pentair intelliflo vs pump. Installed it on monday. Set the thing at 750 rpm and let it go. Got up in the morning, found the pump basket empty, maybe 2 inches of water at bottom, and pump barely pumping. Reprimed,by setting it to high speed, went to work, came home, same thing. Wanted to make sure it wasn't something I did. Today, I cleaned filter, repiped the entire thing and put extra teflon tape on MPAs. Still same problem, filter basket slowly drops down over time.

My old pump was a whisperflo. When it ran, I always had air bubbles in the return lines in little spurts. I could never find the air leak, and just left it alone because it wasn't causing a problem. Now it is. Only thing I haven't checked yet is the valve that switches to the jucuzzi. I am afraid to take it apart and make things worse. Help please.I looked up jandy valve, but mine is much older than the ones pictured. It is under the concrete and accessed through a little man hole cover thingy.

You can't run a pump on low speed, with an active suction leak. Two speed, variable speed -- doesn't matter. A leak that puts bubbles in the basket on high, will regularly kill the prime on low.

The ability of 'self-priming' pumps to handle air diminishes greatly as the motor rpm drops.

membership updated.

I messed with the valve last night after work. It is an Ortega. I think I can hear air being sucked in around the shaft when I move it while pump is in high speed. I am going to try to get some o rings today. The valve is 30 yrs old and has been under extra suction due to the addition of a pool cleaner.

good luck!

Replaced the o ring in valve today. Seems better, but pump is still loosing prime. What should I check next? Is there some other reason this could be happening?

Suction leaks are hard to find, but I don't know of any other option for you. I always caution customers that, when I find *a* leak, that there's no guarantee that it was *the* leak.

Air in the pump basket (on high) and air in the filter (released with the release port, if you have one) will betray the presence of a continuing suction leak.

OK, the problem I am having now, is that I cannot get the vaccum pool cleaner to work. I have been messing with it for 2 days and it is almost like there is a partial restriction in the suction line, and the vaccum puts it over the edge with the extra friction. Is this possible? I am thinking of back flushing it today with a hose and seeing what happens. Wondering if the suction leak was helping pump before?

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Also, I have replaced all above ground piping, super sealed all joints, removed unions, brand new pump, new o ring in 3 way valve. There is nothing left to check except underground pipes. How do I go about this, and what should I be looking for?

You won't enjoy *this* answer:

I've never been good at finding underground suction leaks, myself. If you do find a good solution, before you describe it here, consider whether it's patentable or marketable. If it is, and works well, you may not want to share.

Sorry.

so I dug everything I could up today to see how it works. Found that jacuzzi air pump pipes into suction line. cut and capped it to rule it out. Running now. Will post results.

Good luck! Sounds like you are pursuing this methodically, which is what gives the best chance of success!