Help debugging spa pump

[gkran]

I have an inground pool with spa that cascades into the pool. There is a shared main pump, and a second pump for the spa jets.

The spa jet pump does not keep its prime any longer. We turn on the spa pump and do not feel any pressure. If I briefly apply some back pressure to one of the spa jets and release, it will start to gurgle. A couple cycles of this and the pump primes and when it takes it will put out great pressure.

Does this give any clues to what the problem could be?

The pump itself has not needed service in the last 10 years.
The pump never lost its prime as long as we used the spa monthly. I am ordering new O-rings.

Thanks.

 

[cowboycasey]

it may be a bad check valve, see if you have one of these

How To Select a Pool Check Valve - Overview - INYOPools.com

 

[gkran]

I am back working on this. It seems like it will prime on its own for months and then start to have problems ( perhaps suggesting the is a lid problem?)

There is a check valve with a window.
- The pump has the clear lid with two screws that clamp it down
- The spa pump has a direct pipe in and out that does not join with any other pipes/valves or the filter.
- If I have the main pump switched to the spa, and have the spa pump off, there is water pressure in the spa pump basket (as I loosen the lid, water will spray out)


I replaced the lid o-ring and I turned on the spa pump with the main pump off.

The spa pump primes in surges:
- I will see some water in the check valve window, it slowly increases over a few minutes
- Then there is a rush of water in the check valve and then the water disappears and the pump runs very quiet (can only hear the motor)
- This cycle repeats four or five times, eventually the pump primes and the red gate in the check valve is visible in the window
- When primed, the pump is louder (don't remember if this is normal or not)

I use the spa and then repeat this test on the spa pump a few days later. It behaves the same way (primes in surges )


I haven't detected any obvious leaks. I have never serviced the pump or motor in the 12+ years we have lived here.
I have felt inside the pump and do not feel any debris and the impeller spins freely.


Any ideas what to try next?

 

[kadavis]

Definitely sounds like a suction leak. They can be tricky to find, there are links in this forum on how to locate. Sometimes when the pump is fully primed you can or someone else can turn off and you might see or hear where it's coming from.