Repairing a cracked ABS drain fitting with sealant?

[Jvstevens]

I'm dealing with a 1.5"ABS fitting in a crawl space for a bath sink drain that has a small crack in it that is allowing a bit of water to leak out. Under normal circumstances, I would cut out the offending fitting and rebuild it all with new fittings, but its in a tricky spot with multiple fittings close by on each side of it. Not to mention that it is a very long way from the crawl space hatch. So, not fun getting to it or rebuilding it. Anyone got recommendations on a sealant that could be smeared on the crack to give a long lasting, leak free seal? I talked to a local plumbing shop owner this morning, and he said there is no standard, go-to magic bullet for this kind of thing, but that he did mention an epoxy they sell called Mr. Sticky's Underwater Epoxy Glue. His shop did some experiments with it years ago where they filled some holes and cracks they made in some plastic pipe, and pressurized it to 80 psi, for a long period of time with no leaks. Apparently, it was invented by the Russians for some super top secret project.

I have also tried Loctite PL Marine Fast Cure Adhesive Sealant on a stubborn drip for another problem, and it seemed to work well.

Any advice is appreciated. Thanks in advance.

 

[Jadnashua]

It's generally really hard and unreliable to patch something like this from the outside. Hard to tell you whether it will work long-term or not. While not recommended, KerdiFix is a sealant/adhesive that cures underwater. Not designed for this, but I know people that have used it to repair a pool without draining it. Cleaning things off well first will help, but no guarantees. Your safest solution is to rebuild it. Cracks generally happen when there's stress on the joint. That could be caused by repeated expansion/contraction from thermal changes when no movement accommodation is designed in. Both pvc and abs expand and contract quite a bit with temperature changes, and on a long run, that can become a factor.