Plumbing – Cast Iron to ABS – exterior of cast iron not smooth – how to stop leak at coupling


I have 2" cast iron pipe that is for kitchen waste. I had to cut out a 32" section of the pipe under the concrete slab of the basement because a wye had failed.

I have replaced the cast iron pipe with ABS and used American Valve couplings to connect the ABS to cast iron.

The only problem is the cast iron pipe is not smooth on the surface. After almost 50 years of being under the basement slab it has "junk" and rock pieces adhered to its surface. I have tried to smooth the surface of the pipe but I can't get it 100% smooth.

So the coupling cannot seal perfectly. I still get a little leak around one of the couplings.

Would anyone have any suggestions as how to stop the leak?


Best Answer

One of these ironic things? ("American" Valve - Made in Taiwan...) coupling

You should probably try to smooth the pipe out more - a lot can be done with a narrow strip of coarse sandpaper, sandpaper stripwrapped around the pipe so you can "saw" it back and forth. You can also try really cranking on the hose clamps - if you're only using a screwdriver, you haven't really hit what they can do (but you have to maintain some sense of proportion once you switch to using a socket and ratchet on them, or you'll find the breaking point.)

For sheer desperation, I'm not sure if silicone or beeswax (from a toilet seal ring, of course) would be the better desperation move. With kitchen waste it could get too hot for beeswax.