This crack, in a 4 inch stack, has been slowly growing (an inch a year). Can anything be done to halt its progress or does that section of pipe have to be cut out and replaced?

I think the rusting will continue to spread along the crack line, and as the rust spreads, so does the crack.

It may be worth a try to use an angle grinder to cut a sliver slightly wider and longer than the crack, in the hope of getting rid of all the rusted, then apply a rust inhibitor around the edge of that sliver, then fill the sliver with epoxy. That may have a chance, I think.

To stop the crack, drill a small hole at the end of it. I assume this a vent portion of the cast iron stack. If so most epoxy pastes will close the crack to eliminate odors.

It looks like it's in the basement so more than likely not a vent section. I would combine the above two posts: First drill a small hole at the end of the crack to stop it as hj says, then widen it into a V and epoxy it as sum says. This will buy you some time, especially if it's not leaking now.

Had a neighbor years ago with a piece of cast iron on a horizontal run in the basement....the pipe rusted so the TOP of it was like swiss cheese. Went unnoticed for years until the cesspool filled up, then every time you flushed the toilet the pipe would spray like a lawn sprinkler!

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Not a plumber by trade but a fierce DIYer

That type of crack typically occurs on a section that is very humid, but not wet like a drain, although it can happen there. But if it were a drain, it would leak every time water flowed down the pipe.

That is a drain for upstairs but the upstairs has been unoccupied for a year, so no water has flowed down that pipe for a year except for rain water. That stack goes straight up, unreduced, through the roof.

Does what hj stated imply that the crack might have progressed slower if that pipe had water flowing down it?

I have replaced horizontal sections of drain pipe where the leaks were at the top of the pipe. The bottom of the pipe which had water flowing through it did not corrode through.

I will follow hj's advice and drill holes at both ends. I will also apply epoxy.



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The crack at the bottom is being constrained by the lead joint.