Sealant for black tank outlet to ABS pipe

I made a similar repair using PVC/CPVC/ABS cement and fiberglass drywall tape. Clean the leak area and layer up the cement and fiberglass tape. It worked well on my tank and on two tanks of my son in law's trailer.
Russ

A non-hardening gasket type sealants. It would need to remain flexible

Maybe something like this......


I'm just surprised that any sealant was used. A proper sized rubber sleeve with hose clamps should be a leak proof fitting

Maybe one from Grainger.....LINK

I had grey water dripping out of my bottom (:o ) when I dumped it and after pulling part of the bottom off I found a cracked pipe going to the outlet. The previous owner had tried to fix it with some sort of glue. I wrapped Rescue Tapeon it an then for extra security I wrapped a duct tape over that. I can rest assure it will never leak again.

ABS Repair

I followed the advice in the links from sunlineclub.com

Ground up some shavings from a scrap ABS coupling and mixed them with ABS cement to make a paste. Sealed a crack in my black tank where the drain pipe comes out of the tank. It basically melts/welds the ABS instead of just sticking to the surface.

Your tank and piping should be ABS if they are black. Had a crack at the bottom of the outlet on mine. Sanded and put 3 layers of JB Weld and 40,000 miles and 6 years all was well.