Pump, difficult to prime and kept primed

[lukeswill]

Main Problem: Pump is have difficulty priming at low speeds (1750) and at 2200, it would start struggling around 6pm (7 hours into its cycle). When I say struggling, I mean it would suck water than there would be like a pressure build up than a lot of water come out, than not much out, than some, etc etc. However, at 3400 rpm that doesn't seem to be a problem.

Secondary Problem: I spa would drain back to the pump, in trying to reach equilibrium with the lower elevated pool.

Background/Recent work: My spa is at higher elevation than the pool, so is all the diverter ortega valves. I recently changed the in ground 3 way ortega valves that would diverter circulation from/to the pool or the spa. I have re-sealed it well, with plumbers greases. But now the pump definitely has problems at 1750 rpm (whole point of a vs pump).

See my attached pdf of the pool setup.

I been trying my best to seal everything properly.

 

[msumoose]

So, my $0.02...

There is an air leak somewhere. Have you tried lubing every available O ring (focus on the strainer cover lid)? Also, it says that you have used "plumber's greases"...the consensus here is that all threaded connections get "teflon tape" (which is PTFE tape) for two or so wraps, and then followed up with a PTFE based pipe dope. Oatey Great White is a good, well known brand.

Look at all the PVC connectons: elbows, tees, unions, etc. Look for cracks. Finally, if all of that will not cut it, shaving cream all connections until the pump catches and you will know where the leak is.

 

[Richard320]

Any chance there's air trapped in the filter? That would compress when the pumps are on and then force the water out when off, causing priming problems. It will also require a certain pressure to overcome, and maybe there isn;t enough at low RPM.

 

[mas985]

Main Problem: Pump is have difficulty priming at low speeds (1750) and at 2200, it would start struggling around 6pm (7 hours into its cycle). When I say struggling, I mean it would suck water than there would be like a pressure build up than a lot of water come out, than not much out, than some, etc etc. However, at 3400 rpm that doesn't seem to be a problem.

I would say that is normal and due to the low flow rate the pump is producing which isn't sufficient to purge the air out of the pump basket. Typical priming RPM should be above 2500 and maybe higher depending on the plumbing.

However, losing prime while the pump is off is not normal and you should try and find the leak. Common leaks are the pump basket lid and drain plugs.

 

[lukeswill]

I have teflon all the connections when plumbing the new system back in feb. I greased the seals/o-rings at the oretga valves and pumps. But I am not ruling out leaks either, I believe there's some of that going on.

As for filter... one of the syptom is when i open the pressure gauge relief it helps it prime, but not always. None of this low speed was a problem before I start messing with the Ortega. Maybe I should try that shaving cream trick.

Also could there be a leak somewhere else in the system? like in the pipes in the ground?

 

[msumoose]

I will say that I had a 2 speed pump that would have a growing air bubble in the strainer basket because there was not enough straight run of pipe before the pump. It was sucking so hard that it would pull air from any available source. Changed the elbow in front of the pump to 2 feet of straight run (and increased pipe size) and problem solved. I cannot rule out that there was a leak right before the pump, but that fixed the issue and made it more efficient. May not be your issue, but it is something to think about based on your pics.

Good call on the filter air buildup Richard, I have zero of those around here, so I missed that....