Vent pipe leak at joint - repair options?

[Jadziedzic]

Can anyone offer any suggestions on how to repair a joint in a PVC vent that has a very slight leak (a few small drops in an hour) after a heavy rain? There is limited space to work in (see pictures below) - the leaking joint is at the rear of the tee. The vent line marked "FV" is 2 inch pipe; for reference, the section between the hubs of the two elbows is just a hair less than 2 inches long, while the section between the tee and the rear elbow is about a half inch.

I'm willing to give this a go myself if it a moderately handy DIYer can tackle it, or I'm happy to call in a professional. Suggestions would be appreciated - thanks!

 

[Jadziedzic]

I'm leaning toward cutting out the leaking tee and the top elbow and replacing them with a reducing sanitary tee (pic below) and re-routing the 1-1/2 vent line that enters the bottom of the leaking tee so it now enters the 1-1/2 spigot end of the reducing tee. I can use a couple of 2-inch shielded couplings and a short length of 2-inch PVC to connect the new tee to the existing 2-inch pipe. Does this seem like a reasonable approach?

I could try one of those PVC "leak stop collars" that glue over the pipe next to the hub with the leak, but if that doesn't seal the leak I'll then have to remove the stub from the elbow heading up into the wall to insert a new longer stub - which seems a dicey proposition with 20+ year-old pipe. Or perhaps use self-fusing silicon tape around the pipe and hub at the site of the leak...

 

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[hj]

It would have to be a very POOR joint to leak from the amount of water that would get in to the vent pipe. I am more inclined to believe the leak is at the roof and running down the pipe, then dripping off when the pipe turns the corner. If it is really the joint, just brush some PVC cement around the joint.

 

[Jadnashua]

Sometimes, they just forget to put the cement on the joint! Around here, the inspector wants to see the colored primer to see if, at least they used the cleaner/primer on the joints first. Don't see any of that. They do make a clear cleaner/primer, so that step may have been taken.

The cement has some dissolved plastic in it, and might solve a slow leak. It could be coming from above, as HJ indicates...much more likely.

 

[hj]

Even if there were NO primer or cement, that joint would probably NOT leak even if more water flowed down the pipe than what actually does.

 

[Jadziedzic]

I initially thought this was water running down the outside of the pipe, but after drying everything off I was able to observe the slightest amount of water seeping out of the joint. The joint is definitely glued, and it appears (clear) primer was used during the installation. I'll try brushing on some PVC glue to see if that seals the leak.

If that doesn't fix the leak would my idea of using the indicated tee and couplings be the appropriate/most likely to succeed path for repair?

 

[hj]

The way those pipe and fitting are assembled, ANYTHING you do to replace the leaking joint will entail a LOT of revisions.

 

[Asktom]

"The way those pipe and fitting are assembled, ANYTHING you do to replace the leaking joint will entail a LOT of revisions."

Especially if you want the vents to be legal (which they currently are not). If it is working other than the drip, just wipe PVC cement around the joint and cross your fingers. (Some would use a red hot knife or... nevermind, I won't mention those other ways.)

 

[Jadziedzic]

Thanks for the input, wiping the joint with PVC cement certainly seems like a first repair attempt to try.

Could you please explain further the issue with legality of the vents? Other than the occasional drip as noted things appear to be working fine with the drains (and have been for the past twenty years I've lived here). I'd like to understand what should be changed to bring this into compliance, if for no other reason than to consider if I should get this fixed for the next ten years we'll live here.

 

[Reach4]

The thought expressed in reply #3 about the possible roof leak makes sense. I would try tying a rag etc around the pipe as high as possible. If that gets wet, you know the problem was not due to the joint that you suspected.

 

[Asktom]

The vents should hook together at least 6" above the flood level (where the water would dump on the floor) of the highest fixture connected. As your vents/drains are currently run a clog in the line at certain points would allow the fixtures to drain using an alternate route (the vents). Correcting this would be a huge project, just wipe on the PVC cement and double check that the leak isn't down the outside of the pipe, which actually seems more likely. You might try dumping a bucket of water against the vent pipe just above the flashing without letting any go down the vent as a reality check.

 

[Jadziedzic]

asktom, thanks for the explanation of the venting issue. Your explanation made me wonder how things were actually plumbed, so I dug out the pictures I took when the house was framed.

During construction I asked the plumber to leave provision for a future sink in the basement where I planned to have my workshop; when he was done with the rough-in of the house he pointed out the "FV" marking for a future vent to be used when the sink plumbing was roughed in and a capped tie-in for the drain next to the main stack where it exited the basement. The vent connection wasn't run at this time since I didn't know where the sink in the basement would be located.

That 2-inch line runs to the attic where it ties into the main stack below the roof line; along the way the first floor kitchen sink vent line ties into the 2-inch line at what looks like about 4 feet above the floor level. I'm fairly sure that originally the 2-inch "FV" line tied directly into the side of the horizontal section of drain (i.e., there was no downward-facing tee in the original rough-in), but that's 20 years ago so I can't be sure (and I don't have any pictures of the basement rough plumbing from construction time).

A year or two after the house was built I started on the basement shop and had someone do the rough-in for the basement sink; that's likely when the tee was spliced into the "FV" line. Based on your explanation and the pictures I have it sounds as if instead of splicing in a tee to the "FV" line the tie-in to the horizontal drain line should have been capped and the vent for the basement sink run directly into the "FV" line. That would keep all vent connections (basement sink and kitchen sink) above the flood level of those fixtures.

Perhaps the original connection to the horizontal drain line was to allow condensation that might build up in the vent line to drain out? I remember reading a few days ago about plumbers cutting open "future" vent lines and getting a face full of years-old condensation build-up...

We have rain tonight and more forecast over the weekend so I'll keep checking for water running down the 2-inch vent pipe, but so far it's dry (with still a bit of seepage from the joint).

Anyway, thanks again for pointing out and explaining the venting issue.

 

[hj]

The FV connection was NEVER a proper, or legal, one regardless of whether it was ever used for downstairs bathroom or not.