Pump won't Prime - Need some Ideas

[lovemyazpool]

Hello, my fellow Pool Friends -

I had a weird issue and I was hoping someone might be able to give me some ideas before I dig up my entire pool.
About 5 or 6 years ago we replaced our pool pump, filters, valves, etc, and also switched to salt water. The pump is a Pentair IntelliFlo VF 3HP pump capable of a 10' water column. Over time in the 118-degree Phoenix weather, the valves that were recommended by my local pool store failed and had to be replaced. I was using channel locks and vice grips to turn them. SO i had planned on redoing the valves after this season since everything was still working fine.

About a week or so ago we backflushed the pool and the pump failed to come back on after the backflush. I would need to start twice every once in a while, but never more than that. This time the pump failed to ever prime, regardless of my valve positions and regardless of how many times I primed the pump. At first, I thought it might have been the pump seal itself, but when I prime the pump and start it, it shoots a 2" stream of water out of the output sie of the pump about 8' before running out of the prime water in the basket. I assume that this means the seal in the pump is just fine.

So, next, I thought it must be the Crud valves that I needed to replace:



So we rebuilt the manifold and installed all new Jandy valves:




Unfortunately, that did absolutely nothing for my pump-priming issue. Everything on the output side has been completely disconnected from my pump, so I know it's not something on the output side. It also happens regardless of that valve (or how many) I open. I have three valves: Mains, Skimmers, and Vacuum (we never use this as we have a robotic vac, but I kept it anyway). I can open them all and I cannot prime, I can close them and open them one at a time and I cannot get it to prime, etc.

One thing that I did think was odd is that over the last year we started to get a lot of air bubbles coming out of the water return lines from the filter in the pool. I really didn't think much of it at the time but I want to share all of my observations in the hopes someone has some other ideas. The other thing was that when we rebuilt it a few years ago, you NEVER say air in the top of the pump basket, and over time, it was common for you to see air in the top, a lot of it.

At this point, I am thinking maybe a break in a line somewhere maybe underground that is preventing the pump from pulling a vacuum, but all three lines? Also, when I did the test on just the vacuum line, I put my fingers over the vac port in the pool and when we primed and then started the pump the darn thing practically sucked my fingers into the vac line. So it had, for a second or so, a ton of suction, and then it all quit.


So my thoughts are maybe:

1) Still a bad seal in the pump, good enough to pull a vac when the basket is primed initially, but not to keep it
2) One or more cracks or breaks in the lines underground. We partially dug out all of the lines already to replace the valves (input and output) but saw no leakage to that point.

I would appreciate any sage advice or thoughts on this one, I am a pilot by occupation and have reached my limit of theoretical hydrodynamics.

 

[Pool_Medic]

Firstly, do not open main drain and skimmer when trying to prime, close the main drain, fill the pump basket to over flowing, let a lot run down that line, basket lid back on then turn pump on, you will see the water in the basket be quickly sucked out, depending on how far away your skimmer is determines how long it will take to pull water up that line. It will start with a slow trickle then gradually fill the pump basket, once all air is out of the basket, then you can slowly begin to crack open the main drain valve. Please note how the water drops in your pump basket. Closing and then reopening that main drain will slowly start to pull water from the main drain. I have several pools with long uphill runs and it can take 10-15 minutes to fully prime.

 

[Poolbreh]

Like pool medic said 10’ can take a long time to prime. You installed a check valve before pump so the water won’t fill those pipes completely. If what pool medic said doesn’t work, open skimmer valve only open pump lid, wrap a rag tightly around a garden hose and stick it in the skimmer while holding it. Don’t lose the rag. Try to make a seal the best you can and purge the air out of the lines. Once the pump lid starts to fill the check valve should hold it. Remove everything put lid on and start it up. Only open the other valves very slowly as to not lose the prime.

 

[lovemyazpool]

Just some feedback - thank you for the help, it is greatly appreciated. Even following your instruction did not work. Ultimately I found that a connector from the Autopilot system to the suction side of the pump lines was cracked and drawing in air preventing the pump from priming. After replacing that connector, the pump now primes exactly as it should.