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?



3 Answers 3


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.

  • Yes you found the picture :-). I have already sanded it very thoroughly. The stuff is baked onto the pipe. Silicone might be the answer but I wasn't sure how silicone would adhere to the cast iron and the coupling. I'm might try the ratchet as I only hand tightened, but I don't want it to break :-).
    – RDotLee
    Commented Jan 13, 2014 at 2:23
  • You could add an additional hose clamp if you adjust the position of the rubber coupler so that you can get two hose clamps on the cast iron side. Put the "screw" part of it on the opposite side from the other one for best results.
    – Ecnerwal
    Commented Jan 13, 2014 at 2:57
  • That sounds like a good idea. I'll give that a try tomorrow and post the results :-)
    – RDotLee
    Commented Jan 13, 2014 at 3:24

I have seen pipe as corroded as you speak of. It might be good to grind off the excess rust flakes with a small right angle grinder, or you could use a disk sander. The trick will be to get all around the pipe and the part prone to leaking is the most difficult to get to. Ecnerwal's idea about the emery cloth would work, I would suggest finding the coarsest grit possible, belts for a belt sander would allow a coarser grit to be had, just cut the loop and a strip will be made. I would use 32 grit to start, or at least have it on hand, finer grits would readily clog. I would still use a powered grinder or disk of some sort, then the inaccessible bottom can be cleaned using the strip made by the sanding belt, working it the way Ecnerwal says. Once cleaned up a bit, there is a sealer that I seen plumbers use for the Fernco (neoprene)couplers. A little research and that can be found. It would be handy to preserve the fresh metal that the grinding and sanding would expose.

  • So a strange thing happened (maybe its not so strange). I went to check on my leak tonight and it is not leaking anymore. I wonder if the rubber coupling needed to 'form' over some of the high spots in the cast iron? I'm going to keep an eye on it for awhile (at least a month) before pouring the concrete. I'm looking for the sealer that you mentioned. I might add that for extra durability.
    – RDotLee
    Commented Jan 14, 2014 at 2:33
  • Yes, that could be the case, it has finally compressed itself into place. I did a small search looking for the sealant used online and in a forum, Permatex is a brand name that come up for the sealant, though it did not give the type of sealant Permatex made for this type of joint.
    – Jack
    Commented Jan 14, 2014 at 3:06

If the connectors for the new section have rubber inserts there is a chance they may have dried. I found that spraying with WD-40 works by swelling the rubber.

It may be worth a try to spray inside the fitting before securing.

  • WD40 contains solvents, this will damage the rubber over time.
    – user48735
    Commented Feb 3, 2016 at 22:57

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