New variable speed pump loosing prime at low speed

[lucas2]

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?

[PoolDoc]

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.

[lucas2]

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.

[PoolDoc]

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

[lucas2]

So, this morning pump basket was empty again. Last night I watched it for a while, and what I noticed was the bubbles are now gone coming in from the skimmer. Now what I notice is an occasional large bubble coming up from the pump side. This does not make sense to me. Do I need to turn up the speed? Running 850 rpm and about 5 psi.

[PoolDoc]

Centrifugal pumps can handle more air at high RPM, than at low RPM. Of course, the suction will increase too, possibly causing the leak to increase. But hopefully, there's a higher RPM that will handle air incoming from the leak, without increasing the leak so much that the pump cannot help it.

One other point to consider - as the leak increases, the SOUNDS from the leak also increase. There are some leak detection tools that exploit this, but they are not cheap:
http://www.leaktools.com/mm5/merchan...egory_Code=LD2

You might want to check around and see if someone in your area can perform that sort of leak detection. You may also want to check out these two flow-charts, from that same company:
http://www.leaktools.com/professiona...ion%20Gath.pdf

http://www.leaktools.com/professiona...re%20Test2.pdf

[lucas2]

I own an ultrasonic leak detector designed to detect ultrasonic gas leaks in refrigerant systems. It also detects vacuum leaks. I will try it out and see what happens.