Pool pump not staying prime when suction on pool stays prime when on spa

[ewmcmill]

Hi y'all, I'm new to owning a pool, so far this forum has been very helpful with pool chemistry, however my pool seems to have developed a leak that none of the existing forum posts have been able to help me locate.

I understand that I may need to ultimately call someone out to address/locate the issue, but I'd like to do as much initial debugging in case it is something simple I can fix myself.

The Issue:
Pump loses prime, but only when set to 'pool' mode, when set to 'spa' mode pump stays prime. When set to pool mode the pump will stay prime for about 1-2 mins then large bubbles will start entering the pump from the supply pipe and the pump will slowly drain over the course of about 30 mins.

Seems to have started after I ran the spa bubblers while pump was running in 'pool' mode, not sure if this is an invalid configuration...


Steps I've take to locate the issue:
(please reference attached photos, I have labeled each valve with a number):
Prior to each of the following the pump was set to 'pool' then primed
(also I have ensured that the 'drain' valve is closed, the pump loses prime regardless of drain valve position)
- Set pump from 'pool' to 'spa' mode -> pump stayed prime
- Leave pump in 'pool' mode then close the 'pool' suction valves (valve 2) -> pump lost prime
- Leave pump in 'pool' mode then close 'pool' return valves (valves 5 and 6) -> pump lost prime
- Tightened filter clamp -> pump lost prime
- Tightened filter fittings -> pump lost prime
- Checked for leaks on all pvc joints, can't find any water leaking nor bubbles when running water over the joints
- Inspected pump lid gasket, looks okay but could be bad?

Suspected root causes:
The issue seems isolated to pool suction side before valve 1, but I can't be 100% certain given my lack of knowledge.
- A leak in valve 2 or 3, I can't locate a leak here but doesn't mean it doesn't exist
- Leak in pvc before valve 1, I can't locate a leak
- Leak in pump lid gasket, odd that pump would stay prime when valve 1 is directed toward spa
- Bad check valve? My pool doesn't seem to have any check valves on the suction side, they might be underground?

Let me know if I can provide any more photos or info. Thank you for taking a look and providing your thoughts/opinions/experience.

Suction side:

Full view:

Check valve on return side (after heater):

Above pump:

 

[Poolbreh]

You should clean that filter and relubricate tank oring. Your spa appears to be higher than the pool equipment so it will prime off spa easier. You may just have a bunch of air in the line from the leak at the filter, the water in the pipes is traveling back into the pool. It’s possible your pool is a slow primer. Lubricate lid oring and fill pot and pipe and try to prime again.

 

[ewmcmill]

Poolbreh, I'll go get some lubricant and try to lubricate the filter tank oring and the pump oring.

I'll update you later.

-Erich

 

[ewmcmill]

PoolBreh, I lubed all the orings I could find (pump, filter main, filter gauge). Seems to have helped, losing prime slower. I tested the system after lubing each oring, pump oring didn't seem to help, but the filter main oring reduced the rate at which the pump loses prime. I noticed that the filter main oring seems to be deteriorating, I will order a new one and replace to see if that is the issue.

Thanks for your help so far.