Plumbing - PVC Threaded Union - Slow leak

[meverha1]

As the title says, I have a PVC Threaded Union (return side) with a slow leak (1 drop ever 60 - 90 seconds). It Only affects the "gasket" side of the Union and it seems to leak back down the threads of the union and out the other side.

A couple of things....

1) I've tried several Threaded unions and it each one had the same issue so it may not be the union. Also, I've switched unions around and it always affects the side of the union with the black gasket.

2) I've tried tried teflon tape on the side with the leak. It didn't work. Perhaps I didn't use enough? I wrapped it 5-6 times.

3) I put a bit of vaseline on the gasket and that seemed to stop the leak for a bit (or maybe I just didn't notice it because I was doing other stuff?)

Suggestions to stop the leak? Thoughts on what may be causing it? Is it possible that my PVC is angled in such a way that it's not making a complete seal?

[A sea K]

Sounds like you've been pretty thorough and I would at first suspect the O-ring (gasket), however, vaseline although not my first choice should have helped to seal it and did not. Next I would examine the sealing surfaces themselves for any imperfections that would allow water to pass. Otherwise your idea of the joint itself being out of alignment could also cause the problem then I would say tighten the daylights out of it to see if that helps.

[meverha1]

I'm not entirely sure if the vaseline helped or not. It seemed to for a time but like I said, it may have just been me not paying attention.

Also, I used what I had on hand. Was trying not to go to the store.


A plumber friend of mine told me to just put a bunch of pipe dope on it and that would fix it. Not sure if I want to do that or not.

[JMorris271]

Pipe dope would work but only if the leak is in the thread. More often than not when you're talking about a slow leak like you have, the algae and crud will plug it up for you. Unless it is outside of the box, I would leave it be.

[rocsec1]

Teflon paste could do the trick

[meverha1]

Pipe dope would work but only if the leak is in the thread. More often than not when you're talking about a slow leak like you have, the algae and crud will plug it up for you. Unless it is outside of the box, I would leave it be.

It's currently over my sump so when it does drip, it drips directly into the Sump.


I'm torn between trying to fix it now and waiting a few days/weeks to see what happens. It's a brand new tank so there's no "crud" build up.

I may try teflon paste or pipe dope tomorrow. Will see how it looks in the morning.

[A sea K]

Did you try re tightening it? If the union is out of alignment a bit then some extra pressure might be enough to seal it up.

[meverha1]

It's pretty tight. I don't want to risk over tightening.

[Roccus]

with out actually working on this..it sounds to me like an alignment problem... sometimes ..especially with plastic.. if the pipes are off a slight amount if can influence the mating surfaces and your ability to tighten the collar enough for a positive seal ... sometimes it doesn't take a lot.. I run into this a lot with plastic( PVC) and S.S. unions.. copper and brass are more forgiving... I say this because you have tried different unions and still have the problem... a thin coating of Teflon paste around the mating surfaces may help.. I also like to lubricate the threads with Teflon paste.. sometimes the extra lubrication is enough to get that last little bit needed to seal the leak ...

[CStrickland]

You've got the gasket on the wet side right?

Also, there are two products that plumbers use for sealing drains. One is pipe dope, which goes on the threads to let you tighten it a little further and fill small gaps. The other is plumbers putty which you roll out like play doh and lay under a gasket or sink drain to seal the bulkhead, sort of like how the gasket works. I would not use a gasket after putting Vaseline or pipe dope on it. Just cause I'm not sure how that would affect the rubber, it could be fine.

So, when you put in a sink drain you lay a bead of putty around the edges of the stopper assembly, to keep water from creeping down around the edges; and the pipe dope goes on the threads the same as Teflon tape. A tank drain is a similar design, though I'm not sure putty is reefsafe, I have used it on my tank.

Really it's best to figure out what the issue is. Sometimes the bulkhead has a burr from manufacturing that can be ground away with a nail file, sometimes you just get a bad gasket. But, often these slow leaks resolve themselves as there are lots of fine particles in salt water that can eventually plug it as they are carried into the void and trapped there.

The right tightness is about 1/4 turn past what a normal person can comfortably tighten it to with their fingers.

[biecacka]

If it is over the sump and drips back into the sump, then I'd leave it. Chances are he salt creep will plug it in a few days.

Corey

[Bluefish9]

O ring could be out of position. Also, people LOVE to use cheap, white thread tape for some reason... Go to HD and grab some Oatey fast tape. Its way thicker and kinda sticky. Havent had a leak ever since switching to that. Its a little pricey when compared to a standard roll but in the big picture, $2 is a small price to pay.


Sent from my iPhone using Tapatalk

[A sea K]

OK folks, were dealing with a union here. Unions are sealed with an O-ring and all the teflon tape or pipe dope in the world wont fix it. The o-ring needs to be checked for any imperfections as does the finish on the mating side where the O-ring makes contact, lightly lubricate the O-ring preferably with silicone grease and tighten. If all these check out then the union must be out of alignment and not allowing the O-ring to seal without excessive force.

Three courses of action IMO,
1 re do the plumbing and fix the alignment issue
2 use more force tightening the union and see if it will pull itself into place
3 if its slow enough and the drip is into the sump itself then just live with it, if it is slow enough it will likely seal itself up in time anyway.