Reglue old PVC joint?

[OneStaple]

Hey All,

While doing other work in the attic, I noticed a PVC vent line had a little water coming out of an elbow joint during my wife's shower. Since it was relatively accessible, I cut the corner off and installed a new one.

While installing the new corner, it seemed like one of the PVC pieces was way too easy to move into position. In investigating the next joint down the line (which is very difficult to access), I found that the joint was completely loose and freely rotating. No noticeable damage to the pieces, but it just appears that it separated at the joint.

The joints are probably 35 years old and all the glue on them is clear (or yellowish). No purple primer, but I don't know if that was used back that far. There is glue in/on the joint.

Some researching has suggested that I can reglue the joint with generous amounts of primer/glue after cleaning it. But most of the research related to recently glued joints that separated/failed for some reason, rather than 35 year old joints. So is it safe to sand/scrape off what I can of the old glue and reglue the current pieces? Or do I need to look at cutting back and replacing in this inaccessible area?

Again, this is a vent line, no fixtures draining through this section (other than condensed steam).

Thanks,
Tyler

 

[Reach4]

Some researching has suggested that I can reglue the joint with generous amounts of primer/glue after cleaning it. But most of the research related to recently glued joints that separated/failed for some reason, rather than 35 year old joints. So is it safe to sand/scrape off what I can of the old glue and reglue the current pieces? Or do I need to look at cutting back and replacing in this inaccessible area?

I am not a plumber, but I think that if you can loosen and rotate by hand, you probably don't need that much prep.

The newly primed and glued joint may seat deeper, so you may have to add a shielded coupler to one of the pipes to let you stretch that pipe a bit.

I have used Gorilla PVC self-priming PVC glue for some non-plumbing PVC. It is a bit slower to set than the regular. The regular is nearly instant. The Gorilla is not slow but it is slower.

 

[Sponsor]

 

[Terry]

If the pipe fits in, you can prime and reglue. Did they even glue it in the first place? You don't normally see pipe that can swivel in a joint.

 

[OneStaple]

Well, they smeared something on the pipes that resemble glue, I think. As I said, no obvious primer though. Given that two joints next to each other were bad, it makes me nervous about all the other joints throughout the house.

I'll climb back up in the attic (gah, I hate that cramped attic) and reglue it tomorrow night. I'll try to get a couple pictures while I'm there just so people can see.

Thanks!
Tyler

 

[Jadnashua]

A proper pvc joint doesn't really use glue...it's cement. It's technically a solvent welded joint...the cement and primer literally cause the top surface of the material of the pipe and socket to melt and flow together. The cement also has some dissolved plastic in it, so that when the solvent evaporates, the two pieces become one. It sounds like someone did use glue, and it failed. A solvent welded joint should not. The drips in the attic were probably from condensation, but it could also have been from precipitation if it was falling.

 

[OneStaple]

Ok, I snapped a few pictures. First is of a nearby joint. Second is the elbow I already replaced. You can see gaps where there appears to be no glue/cement in the joint. Third is the joint I reglued/recemented tonight.

When I reglued the joint tonight, I used a liberal amount of primer and glue, but I didn't get a warm fuzzy about the connection when it was done. I didn't want to stress it, but it didn't seem as snug as it should have been. I put paper towels on the pipe just under the joint so I can check in a day or two for wetness.

Tyler

 

[Jadnashua]

If you try to make a joint up with cement that has turned to a gell verses it's normal, more soupy consistency...there's not enough solvents in it to melt the plastic of the pipe or fitting, and the bond will be very marginal. It also won't flow so you get a good, even coating. Once you have the pipe out of the fitting, you'd want to clean it up as best as possible in case whatever was used is preventing the new cement from melting things so a solvent weld can occur. Whatever was there, may not be properly cleaned off to the bare plastic., which would not make a good joint.