Pentair pump stopped priming or passing water

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samiam95124

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Jul 4, 2016
27
San Jose
I have been through a lot of years on this pentair we-2 pump. Normally prime and run is no issue. I came home and no water was moving. Opened the volute and the water was boiling, apparently because the water was not cooling the motor.

This one has me puzzled. The motor runs fine, I took out the motor and impeller and it was clear of debris. I ran it as separated from the volute, runs fine. The impeller and motor turns without friction. I got a seal kit for it, and replaced the volute o-ring even though it looked fine. The seal between the volute and the motor housing also looks fine. It just does not prime, and it used to prime like a train a day or so ago, I have never had an issue with it. This pump has been operating fine for 5 years.

I tried some obvious stuff. There are two intakes, tried both of them so the input is not blocked. My next guess is that the front pump seal failed, and I am replacing that. I pulled and put the pump on a bench to replace that according to online instructions.

My question is, could the pump shaft seal be the issue? It seems to be taking in air from somewhere, but I went all around the system and couldn't find any obvious suction side leaks.

Thanks in advance.
 
Sam,

I believe that what causes the water to get hot and boil, is when the pump is unable to send the water down stream.. So the same water is just churned by the impeller and gets really hot. It can get so hot that it can melt, or warp, the volute and the lid rim..

Show us some pics of your equipment pad...

Thanks,

Jim R.
 
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samiam95124 said:
Opened the volute and the water was boiling, apparently because the water was not cooling the motor.
Click to expand...
I just want to make sure exactly what you did so lets first cover some definitions.



1716819457768.png

It sounds like you opened the pump basket lid, not the volute, is that correct? The volute contains the impeller and the exit port of the pump. Was the water boiling in the pump basket or the volute?

But I agree that most likely, the flow has stopped. Have you made sure all valves on the suction and return side are open?
 
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Hi thanks for the replies. Yes, I was referring to the pump basket. Everything is open, and this occurred while the system was running and passing water. It was double checked with one of those drain purger things, fits on a hose and expands. There are two intakes leading to a valve in front of the pump, and both sides were checked as well. Also, I took the ring off that holds down the pump lid and just put the pump lid on and pushed it down by hand, then removed it. I was expecting it to release with a "pop" if it had suction, but nothing. I am in the process of replacing the pump seal (in the diagram above). Will post a picture.
 
A bad pump seal would be leaking water. I don't think that is the problem.

Are your sure there is not a clog in the impeller and/or suction line?

Something is preventing the pump from priming which is causing the overheating.
 
samiam95124 said:
Hi thanks for the replies. Yes, I was referring to the pump basket. Everything is open, and this occurred while the system was running and passing water. It was double checked with one of those drain purger things, fits on a hose and expands. There are two intakes leading to a valve in front of the pump, and both sides were checked as well. Also, I took the ring off that holds down the pump lid and just put the pump lid on and pushed it down by hand, then removed it. I was expecting it to release with a "pop" if it had suction, but nothing. I am in the process of replacing the pump seal (in the diagram above). Will post a picture.
Click to expand...
Yes a bad shaft seal can cause a pump to not prime, have seen it many times. More likely, though, it is the lid O ring needing lube, cracked and needs replacing, or it is missing if the plumbing is clear and the inlet to the pump is sealed.
My neighbor, a very nice gentleman, had the same issue, wanted to try it himself, even bought a new booster pump because he thought that his was broken and cracked a fitting while installing the new hose fittings (NEVER thread a male pipe fitting completely into a threaded fitting). Cut up his plumbing to try a repair, bought ABS pipe to repair (it doesn't work that way) and the wrong glue. Destroyed a filter adapter and has a pool that is getting cloudy.
Finally, he let me know what is happening on Friday. Replaced the lid O ring and the pump primed and started moving water immediately. Just had the new filter adapters delivered and will be re-plumbing his equipment this afternoon (yes, on Memorial Day). His grand kids want to swim.
EVERYTHING takes lubrication to work.
 
The seal is on the pressure side of the pump. In order for that to cause a priming issue, it would have to be significantly leaking and you would definitely see that.
 
mas985 said:
The seal is on the pressure side of the pump. In order for that to cause a priming issue, it would have to be significantly leaking and you would definitely see that.
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Absolutely, when the pump is moving water. More likely to be another issue in this and most cases.
But it does happen or I have been cheating customers for many years and cheating myself out of the profit of a larger repair bill. And yet, replacing a shaft seal solved the issue at least 50 - 100 times over the years. Go figure.
When the pump is not moving water there is no pressure inside the pump body/tank and it doesn't take much of a leak of air to stop a pump from priming. When there is no pressure in the pump, water may not leak from a bad seal, but air certainly can be drawn in.
 
1poolman1 said:
Absolutely, when the pump is moving water. More likely to be another issue in this and most cases.
But it does happen or I have been cheating customers for many years and cheating myself out of the profit of a larger repair bill. And yet, replacing a shaft seal solved the issue at least 50 - 100 times over the years. Go figure.
When the pump is not moving water there is no pressure inside the pump body/tank and it doesn't take much of a leak of air to stop a pump from priming. When there is no pressure in the pump, water may not leak from a bad seal, but air certainly can be drawn in.
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I just don't see how that is possible. Even when priming, the pressure side of the pump has some positive pressure. The impeller is moving water from the suction side of the pump (impeller eye) to the pressure side of the pump (impeller outer rim) during the recycling process. This decreases the pressure in the suction side and increases the pressure on the pressure side. This is why a pump primes. This should even happen without a seal.

If you want to prove this to yourself, open the pump basket then close it, put a pressure gauge in the drain plug on the pressure side of the pump and turn on the pump. You will immediately see positive pressure.




Note that is this video there is no mention of shaft seal failure as a cause.
 
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Here is a test with my pump and a vacuum/pressure gauge that shows the startup pressure of pump with a drained pump basket. It never goes into the suction region.

20240527_133209.mp4

It is possible that the recirculation port was clogged and when the pump basket is drained for repair, that clears itself.
 
mas985 said:
Here is a test with my pump and a vacuum/pressure gauge that shows the startup pressure of pump with a drained pump basket. It never goes into the suction region.

20240527_133209.mp4

It is possible that the recirculation port was clogged and when the pump basket is drained for repair, that clears itself.
Click to expand...
A working NorthStar! And it sounds good. Those were amazing pumps. Many times Hayward recommended another model of theirs (the TriStar was just coming out) for a particular application as they were "too much pump."
 
They don't get much love on the forum. Mine is 18 years old but is a spa jet pump so not running that much. But it is a great jet pump.
 
@mas985 and @1poolman1

Here is one from today. Wouldn't prime, changed the shaft seal, good to go...debate closed for me, this is my fourth pump prime resolution with this exact problem. Doesn't mean this is the first line of investigation, o-rings and connections/clogs are first.

New pump won’t prime..

In opening this year, we discovered our 11 yr old Hayward 2 hp Super Pump was locked up. We replaced the motor only, as the pump housing and all were still solid. We did replace the o rings and gaskets though, including the pump basket ring. However, we can not get it to prime. We have done the...
www.troublefreepool.com www.troublefreepool.com
 
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jly62 said:
Replaced with new, gave all gaskets another good coat of silicone lube, put it all back together. Filled the pump pot, turned on just one skimmer, hit the switch….. instant prime!
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Might the fact that the OP lubed all of the gaskets be the reason the pump now primes? I am not saying the shaft seal should not have been replaced as it was clearly damaged, only that the shaft seal may not have been the cause of the priming issue.

Correlation does not always reflect causality. When shaft seals are replaced, seal kits are often used which also contain other gaskets which could be the cause of the air leak.

Also, as I pointed out earlier, the priming vent between the suction and pressure side of the pump can get clogged preventing priming and when the motor is removed from the wet end, this can clear the clog. To me, this is far more plausible than the shaft seal.
 
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Great answers in this thread.

So some yes, some no on the pump seal. I am in the "if I fix everything, it will work" mode. I did try an additional test of interest. I put a plastic bag over the pump basket lid, and held that tight, with air in it. It slowly sucked the air out of the bag, so showed some air was passing though the lid, but didn't seem to be enough to ruin the suction of the pump.

So I am in process of replacing the seals. There is one on the impeller, and one on the motor shaft. I'll try to post some photos today.

Note that I previously replaced the front bearing on this pump. In that case, the bearing was clearly seized, it would not move.
 
samiam95124 said:
showed some air was passing though the lid, but didn't seem to be enough to ruin the suction of the pump.
Click to expand...
You would be surprised. It doesn't take much air at all at all to interfere with the priming process.
 
samiam95124 said:
So some yes, some no on the pump seal. I am in the "if I fix everything, it will work" mode. I did try an additional test of interest. I put a plastic bag over the pump basket lid, and held that tight, with air in it. It slowly sucked the air out of the bag, so showed some air was passing though the lid, but didn't seem to be enough to ruin the suction of the pump.
Click to expand...
Sounds like an issue with the pump lid. Have you tried pool lube?

If you want to try one more thing before replacing the motor seal, try this:

Remove the pump basket lid
Remove the pump basket strainer
Remove the suction side drain plug and flush out all of the debris that is in between the pump basket and housing
Lube suction side drain plug gasket and reinstall
Fill the pump basket up to the level of the inlet pipe
Remove pressure side drain plug and let the water in the pump drain out
Lube the pressure side drain plug and reinstall
Reinstall the pump basket strainer
Fill pump basket up to inlet pipe
Lube pump basket lid gasket and reinstall
Try priming the pump

Also, one other question, how high is the pump above water level?
 
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Just an FYI, it's important to examine the back of the impeller where the ceramic half of the seal inserts.
That can be slightly deformed (expanded) from the excess heat, and will not hold the new seal properly.
 

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