Replaced pool pump union o-ring, now leaking 10x worse

pcm2a

Well-known member
Aug 25, 2017
159
Mt Juliet, Tn
In my other thread I replaced the lid of my Northstar pump to fix the air leak. Once I did that the union on both ends would leak just a little water when you turn the pump on or off. Easy fix right, just put a new o-ring in it. I got them in today, it was easy to undo the union with a strap wrench. I greased up the o-rings with magic lube. Put them in, tightened it back. When I turn the pump on or off water is squirting out pretty badly now. Am I missing some trick to tightening these just right? Move it too much and it comes loose again.

Should I have put the magic lube on it? I will go try cleaning that back off. Going to be freezing tonight so hopefully can get a fix to get to tomorrow.



Update. I let it run so all the air would get out of the system. Here is a video turning it off and one once everything was running smooth. Not how it should be. It's like there needs to be an extra gasket or a bigger o-ring. It is identical in size to the one I removed.

 
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pcm2a

Well-known member
Aug 25, 2017
159
Mt Juliet, Tn
It just sits down on a little ledge. I'm not sure how it could be off? I wasn't supposed to fit it to the male (top) piece was I?

I've also tried wiggling the pump forward, left, right, etc to see if that makes any difference. Not really any difference.

The fact that I can tighten and losen this union by hand seems fishy? Seems like it should seal tighter maybe with a strap wrench.
 

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pcm2a

Well-known member
Aug 25, 2017
159
Mt Juliet, Tn
I am not sure but the union fitting only does so much. You turn it a little bit and it gets tighter, tighter, tightest, then lose again where you can remove it. It's not like a screw on. I could try to find a random gasket to stick in between.
 

pcm2a

Well-known member
Aug 25, 2017
159
Mt Juliet, Tn
Everything I have looks exactly like that picture. I bought a generic gasket for a sink from the hardware store. Tomorrow I'm going to trim it down and put it underneath the o-ring. My hope is to tighten up the area just a little bit to prevent the disaster that is happening.

Since it's going into freeze mode tonight, I've also rigged up my valves so it will suck from all lines and I've turned both pumps on. What I am trying to prevent is it turning off every 30 minutes to switch into spa/pool mode and spewing water all over the place. I think I'll make a separate thread about my "freeze mode" plan to see what everyone thinks.
 

wireform

Silver Supporter
In The Industry
Aug 15, 2017
496
Spring Valley, NY
Something of what you said earlier seems problematic. Your words " tight, tighter, tightest and pop" or similar. That should not pop and just get to a very tight position. How's that getting loose. Is there something cracked on both fittings. Seems someone over tightened it and possibly broke it somewhere where it's not evenly going down onto the O ring
 

Costas > DownUnder

Bronze Supporter
Dec 17, 2017
621
Adelaide | Australia
Does the pump outlet line up nice and parallel (and close) to the incoming pipework?

Ideally the mating surfaces need to be fairly close to being nice & parallel to each other, otherwise as you tighten the outer ring it can get tight at some point before the O-ring itself has seated correctly home due to side pressure on the threads.
 

pcm2a

Well-known member
Aug 25, 2017
159
Mt Juliet, Tn
Something of what you said earlier seems problematic. Your words " tight, tighter, tightest and pop" or similar. That should not pop and just get to a very tight position
Scroll up a bit and look at the picture of the union. It's not a threaded kind. It's made to turn forever.

Does the pump outlet line up nice and parallel (and close) to the incoming pipework?
Looks lined up to me. With the union piece pulled up it's sitting flush. I've tried scooting the pump a millimeter in all directions that it can move but that just makes it not flush.
 

Rich D

Bronze Supporter
Aug 3, 2018
583
MA
I am not familiar with that type of union However it sure looks like that o ring needs to be pushed up around the the top of the tapered portion so it seals the flat surfaces. I have never seen a o ring go on a taper like that.
 

pcm2a

Well-known member
Aug 25, 2017
159
Mt Juliet, Tn
I tried that at one point yesterday but with the thing greased up with the magic lube it would just pop right off. I'll wipe that off and try again. I don't see how it could make anything worse than it is. If that fails I also purchased a generic gasket that I will try putting under the o-ring to make it a little taller. My thought being that might tighten it up a little more. Terrible idea I know.
 

wireform

Silver Supporter
In The Industry
Aug 15, 2017
496
Spring Valley, NY
I tried that at one point yesterday but with the thing greased up with the magic lube it would just pop right off. I'll wipe that off and try again. I don't see how it could make anything worse than it is. If that fails I also purchased a generic gasket that I will try putting under the o-ring to make it a little taller. My thought being that might tighten it up a little more. Terrible idea I know.
Try this. Line it up well and lift the union collar up. Observe if top and bottom flagged portion sit parallel and touching. If they're not touching put some hand force and see what it takes to bring it together. What I'm getting to is if they're touching flat to flat or a tiny gap which comes together easily by hand, that tells me there won't be enough pressure to stop water from coming through. Possibly the o ring is the wrong thickness /size.
 

pcm2a

Well-known member
Aug 25, 2017
159
Mt Juliet, Tn
It's flush all the way around. I have tried scooting it to the left and right a little, but it seems lined up right to me. Below is a picture all the way around it. Also below is a picture of the new (left) and old (right) o-ring. They are identical in shape, size, thickness. I put a new o-ring in the suction side and it is not leaking.

Now for the questionable business...I got this gasket from the hardware store. I trimmed it down to the size of the ledge that the o-ring sits on. Laid it on the ledge and then put the o-ring back in. My hope was to make it seal up a little tighter. You can see the gasket in the picture below. I put it in, fired it up, no water squirted out, no leaking. I'm not sure if this is a long term solution.

My only guess is due to the age of the pump housing and pipes, along with the cold weather maybe, the correct size o-ring is not big enough to make a good seal. Before all of this it probably didn't leak because all of the pressure went out of my old and busted lid.

Video of it running with the red gasket + o-ring


Photo of the new (left) and old (right) o-rings:
Screen Shot 2019-11-10 at 10.43.37 AM.png

Photo of the pipes together:
imgonline-com-ua-collage-KYkk0EsbFX.jpg
 

pcm2a

Well-known member
Aug 25, 2017
159
Mt Juliet, Tn
I don't follow that at all. The red gasket and the o-ring are both inside the union contraption. I think the best fix would be this exact same size o-ring but 5% bigger. I'm not sure how I would ever find that though. Maybe a pool shop could find a random one that is a little thicker? There is a picture of how it sits in there up above: https://www.troublefreepool.com/attachments/img_20191109_155926-jpg.122459/