main waste leak


Old 09-03-19, 07:03 AM
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main waste leak

Looking at my 4" drain in basement- it looks like there is a small leak..... I believe it's cast iron- Is there something i can use to patch?
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Old 09-03-19, 09:57 AM
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Can you see where it's cracked or rusted through? Sometimes a little leak in cast iron is a precursor to a larger one...

If it's really just a small leak, you might be able to use JBweld (epoxy with the consistency of play-dough) to seal it. I'd try cleaning it the best I can to get good adhesion. Doesn't hurt to try!
Old 09-05-19, 09:46 AM
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I suspect the cast iron leak is in a stack that is at least 50 years old. I would also try cleaning the area well with a wire wheel and placing a small patch of epoxy on the leaking spot. Once the epoxy cures, it can be filed or sanded smooth. Cast iron is somewhat porous so these leaks are somewhat common when the pipe ages. Multiple leaks will sometimes require replacement of the entire stack.
Old 09-05-19, 10:17 AM
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I just replaced a 20-foot section of cast iron that had several spots where it rusted through. Project started out that I was just going to replace a small stretch of 2" galvanized pipe running from my kitchen sink, but when I pulled the paneling off the wall to tie into the cast iron I saw all the rusted-through spots. It was even rusty where it exits the house so I had to dig outside to get to good pipe.

I was very surprised, because on the other side of the house the cast iron that is fed by 2 bathrooms is pristine, so I'm guessing that 60 years of increasingly poor drainage through the galvanized made the water and small food bits not flow all the way out, so it rested in the cast iron and eventually rusted through.

Tap the cast iron with a metal tool - if it rings, it's in good shape and you can probably get away with a patch but if all you hear is a dull thud it indicates the need for replacement of that section, at least.

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