DIagnose Booster Pump losing prime

[gkran]

The booster pump for our spa loses prime. Over the past few years, when we used the spa once every couple weeks (sometime longer) it would catch and run fine. If we hadn't used the spa for many weeks, I would have to re-fill the pump basket once and it would run fine. The last few times, I had to refill the pump basket up to 10 times before it would finally catch.

I had a repairman look at it, and wanted a sanity check on his opinions. He didn't think it was an air leak since it still pumps; he thought an air leak would hamper the pumping capability. He believes it is a stuck back flow valve. Also, he thought it was strange that there is a back flow valve on both sides of the pump, since the pump is not that much elevated from the spa. He wants to replace the first back flow valve (it is up to 20 years old) and remove the second.

I want to make sure the solution fits the symptoms. My first thought: the pump requires the back flow valve to retain prime (although our main pump didn't have a valve until last year). In the past the valve would not completely shut off, and the water would slowly drain back into the pool. Now the valve doesn't close at all.

Any thoughts?

 

[mas985]

Check valves can and do fail so that is defintely a possibility. When you say booster pump, is it really a booster pump in series with the circulation pump or is it a stand alone jet pump on it's on loop? If it is a separate pump for the jets, do the jets feel weaker than they used to?

Also, your repairman is correct in that the pump should only require a single check valve although it should remain primed even without a check valve so I'm not sure why they have one at all. The only way a pump can lose prime is that air enters the plumbing from somewhere. Priming the pump is a bit more difficult without a check valve when the pump is a good height above the water so how far above the water line is the pump?

 

[gkran]

It is a stand alone pump, not a booster. I would estimate the pump is 5 feet higher than the water level.

I will probably change the valves and see how it goes.

 

[mas985]

The five foot height is probably why they installed the check valve. It makes priming a bit easier and cleaning the pump basket. I would keep the one on the suction side but remove the pressure side since it is serving no real purpose. That way the suction line will remain primed even if you remove the pump basket lid.