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Removing/Replacing Cast Iron Vent Stack to Polyurethane-Inject Leaking Foundation Cra

1288 Views 2 Replies 2 Participants Last post by  greenfrog5
New homeowner (8 mos) and have been a reader since then, with many successful projects in such a short time. Finally I have a unique situation I'd like some more personal advice on:

I think I'm pretty straight on the poly-injection part (once I can get to the crack) - its fairly straightforward. The problem, is that the crack runs up tight behind an old cast iron vent stack that comes off the main drain line in my basement.

The crack starts about 8" to the left of the pipe near the floor, rises up about a foot, and wanders behind the pipe stack, then straight up to the bottom plate. It leaks and I need access to inject it. There is a stud/drywall build-out that covers the foundation wall, has sink,plumbing/etc adjacent, and a capped gas valve there too. I suspect this was an old dryer hookup with the dryer vent there and a washer hookup on an adjacent wall.

I've read up on cutting the pipe, I have 4.5" angle grinder and metal cut-off blade. I'll get a full face shield and hope that I can cut the pipe at about the level of the top of the gas valve. I need to cut it there to access the whole crack. I know the pipe will be pretty heavy, and might want to pinch my cutting blade - I'll take precautions...

Pipe is ~2.25" dia. The bottom is slightly rusty where it becomes buried in the slab, probably from the leaking crack. It has a rubber cap w/ worm clamp on the end. I was planning to reuse the rubber cap w/ clamp while the pipe is shortened and I'm working behind it.

The drain line (buried in basement slab) runs downstream (left in photo) and picks up other fixtures on the way to the sewer. Upstream (right in photo) is a sink (pictured), and I don't think anything else (possibly upstairs kitchen sink + washer). I suspect this stack is intended to be above the basement sink (in photo), and I should raise it back up when I'm done working? I was going to get appropriate ABS or PVC ('sewer' rated?) pipe in similar size, and a no-hub connector to transition from 2.25" cast iron to new-size PVC/ABS. Then I get a 135-deg bend and an AAV to install at the top?

Am I missing anything here? Will I be able to cut this with a grinder without damaging adjacent stuff? Is damage to the slab, or pipe down into the slab a concern? Renting a pipe breaker is a possibility if it will be THAT much easier/safer. Any other details about plumbing parts? Type of pipe, etc?


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Use a 1/4" drill and drill several holes in the lead that holds the 2" riser into the pipe hub near the floor. Once you have removed as much lead as possible- gently wiggle and lift the pipe out of the hub. Now clean the inside of the hub and plug it with the appropriate sized plug until you've finished the foundation work.
Thank you for the alternate advice.

How do I extend the pipe back up when I am done? I have to solder new metal pipe into the hub?

Is there a risk that I drill/damage the hub, causing further headache since it is buried in the slab?

Is there a specific type of 'plug' that is appropriate?

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