Losing prime when I shut off pump

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N

Nafizur

0
Jul 7, 2013
24
Brampton, ON
Hey guys,

So here is the deal. I run my pump for 5 days straight and it's going strong. No issues at all. I look at the pump basket and I can see water topped up and everything. If I turn off the pump and I turn it on next day or even few hours, I will lose prime. I have to go back to the pool skimmer and use my priming tool and use my water hose to feed water into the line and it will start back again within minutes. When I push water through I can see bubbles from the return line and eventually it goes away once it has good prime. I'm not sure why this is happening but it's getting annoying because I have to prime every time I turn off the pump.

Also, when I vacuum the pool, after 15-20 minutes of vacuuming, I will start to lose prime as well. The suction is weak.

I attached some pictures and photos of how the pump looks when it's running. Doesn't look like any air leaks

Dropbox - photo 2015-07-06, 11 33 30 am.jpg

Dropbox - video 2015-07-06, 11 34 03 am.mov
 
Only way for the pump to lose prime is if there is a leak somewhere that allows the air into the system. It could be on the suctions side (pump lid, etc) or on the pressure side (like a filter fitting). The pressure side leak is not always obvious because it may not let water out when pressurized, but could let air in when the pump shuts off.

I suggest you get it primed, then turn off the pump and see if you can hear air getting sucked in anywhere.
 
I turned off the pump but I don't see any air getting in. There is still water in the pump basket when I turn it off. However, if I come back after 30 min, the water is almost gone from the pump basket.

Where else can I check for else. I made sure the lid is extremely tight.

Is there anything I can do to figure out if there is leak on the pressurized side?
 
You need to listen for the air being sucked in.

Do you see bubbles entering the pump basket? Or does the water level in the pump just slowly drop? And does it start dropping right away or does the filter have to drain first.

You need to stay there for the 30 minutes and try to figure out what is going on.

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This is a good step by step guide on suction side leaks: Pool School - Suction Side Air Leaks

Sometimes a soapy water solution on joints or connections can pinpoint a problem as bubbles get sucked into leaks. This works better when the pump is running and there is more suction on the lines. With a fairly small leak that's only exhibiting symptoms when the pump is shut off, it may be harder to pinpoint, especially as jblizzle said, it could be on the pressure side, but have "suction side" symptoms when the pump is off. It's much more likely to be a fitting that you can see than an underground problem but will no doubt be maddening until you find it.
 
JVTrain said:
This is a good step by step guide on suction side leaks: Pool School - Suction Side Air Leaks

Sometimes a soapy water solution on joints or connections can pinpoint a problem as bubbles get sucked into leaks. This works better when the pump is running and there is more suction on the lines. With a fairly small leak that's only exhibiting symptoms when the pump is shut off, it may be harder to pinpoint, especially as jblizzle said, it could be on the pressure side, but have "suction side" symptoms when the pump is off. It's much more likely to be a fitting that you can see than an underground problem but will no doubt be maddening until you find it.
Click to expand...

Thank you. Will try the steps above and will report back.
 
borjis said:
I had a recent losing of prime daily and it turned out to be that my check valve between the pump and filter was broken.

new one fixed it right up.
Click to expand...
It is very strange to have a check valve between the pump and filter ... and if you had problems when it failed, then it must be masking some other issue. There should not be a need for a check valve anywhere to prevent the pump from losing prime.
 
Okay, so I stopped the pumped and watched for leaks. Didn't really see anything. The water in the pump basket didn't really go down. Just a little. I waited 6 hours.. Came back and water level is the same. I turned on the pump and it seemed to have retained prime somewhat. I noticed after I started the pump, the return line blew out some air (saw bubbles) and then was pushing out water fine

However, on the pump basket, there is this big empty spot... I can't explain it. You have to see the attached picture. Does that represent a leak or air?

Dropbox - photo 2015-07-07, 8 34 23 pm.jpg

Dropbox - video 2015-07-07, 8 34 41 pm.mov
 
As others have suggested, you likely have a tiny pressure side air leak. It's a leak that only happens when the pump is off (not under pressure) and it lets air into the plumbing somewhere. You cannot see this leak, but it may be possible to HEAR the leak. Everything must be off and quiet (no lawn mowing or kids playing - it's got to be dead silent) and you have to listen for a gurgle or some subtle groaning sound.

If you can't HEAR the leak then you have to fix it by a process of elimination, by resealing every possible entry point. Coming off your pump, you have a threaded fitting, you have a union coupling, you have several glued joints, you have a section of metal flex pipe that has a couple of different kinds of gukem-pucky wiped at its ends (very suspect) and then you have the multipart valve at the top of the filter and so forth and so on.

Since you have so many potential leakage points, that's why it's been suggested you try to narrow things down by sitting there in silence, listening for it's location. A teenager with good hearing might be helpful. They can hear all sorts of things adults can't.
 

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You have a pressure side leak which causes the water to flow back to the pool since the check valve is broken. I hate to be a killjoy but the check valve should have been installed in front of the pump. In that place, when you clean out your pump basket, then the pump will prime easily.
 
okay guys, update.

so i shut off the pump and tried to listen silently. so from all the joints, i didn't hear anything.. no air leak or anything. However, i placed my ear on the dial/valve area of the sand filter.. u know the dial u turn to select filter, backwash, drain, whirlpool.... that one.. i can hear a "shhhh..' noise.. it's definitely not water moving, but there is definitely a sound... the water level on the pump basket doesn't go down though.. but there is definitely a noise in the dial area... any thoughts??
 
I'd be more inclined to think that it might be leaking at the pump shaft seal... I've had this happen before and you can't hear it without a stethoscope ... it is more problematic with I ground pumps than above since typically most above ground pumps have a couple psi against the seal from the weight of the water (head), while in-ground have a vacuum since the pump typically sits above the water level...

If it is the spider gasket, they are typically a few dollars...
 
Did a bit of research on what the spider gasket is. It didn't look that complicated. I'll be taking off the screws and checking it today or tomorrow. If that's the issue, I'll change it.

If it's the pump shaft seal, I don't think I'll do anything as it's inside the pump.
 
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