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I've got a number of pinhole leaks in a section of cast iron drain piping I need to repair. (I know eventually I'll need to replace the sections--Im looking for a temporary fix that will last a year or so until we've saved enough to have it done right.) The pinholes are covered with scales, but on the advice of a friend I scraped and wire-brushed them off. He said then to kneed the epoxy into a ball then work it into the hole. However, now that I have the scales off i see no hole (I guess because on the outside its a pinhole). Should I press the putty into the area where tge he was or attempt to drill it out with a small-diameter bit first?

This is a question simar to How can i repair a nail head size leak on a vertical cast iron sewer pipe in my basement but I'm asking a more specific question.removed scale

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Eden
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  • I believe the purpose of drilling out a hole is to let the patching material "mushroom" a bit inside the pipe, to physically anchor itself on that side. So the question would be whether you think the patching material -- epoxy putty, in this case -- will adhere well enough to make a reliable seal without that. – keshlam Oct 15 '16 at 20:00
  • My guess is that if it were just a line (not drilled out), it would adhere to the outside but not inject itself into the pipe. That's probably not strong enough, but I honestly was hoping it would be since drilling into the pipe makes me nervous – Eden Oct 15 '16 at 22:02

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You know that you're dealing with a structurally-unsound pipe that could fail at any time, discharging the most entertaining sludge in the process. I'd be oh-so-very-careful not to disrupt its integrity. Drilling into it would count; I'd say even scraping and wire brushing could hasten its demise.

Assuming this pipe is under no pressure, then just about anything that adhered to the pipe would block the leaks. I would suggest using patches of good quality duct tape on the holes (if you can find them), followed by a wrap of electrical tape (stretched well) to hold it all in place.

Daniel Griscom
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If it were me, I would be wrapping the pipe with fiberglass, not just sticking goop on it, in which case drilling the holes out bigger would be kind of pointless.

You could use something like this.

If there are pinholes in that pipe, there is more widespread rot in the inside (aka rust), just like Daniel Griscom is saying, and the pipe could be one unfortunate minor event away from decorating it's surroundings.

I would be evaluating how to replace that pipe with ABS or PVC, as well.

Craig Tullis
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    ... I like "decorating its surroundings"... – Daniel Griscom Oct 16 '16 at 17:32
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    Eventually I will replace it, but where we live if you pull a permit for plumbing you also have to upgrade the water main to 3/4 in (ours is 1/2 in now) which would require $5000 we don't have (on top of the $5000 to replace the drain line). Thanks for the link--i like something that physically wraps around the pipe versus just sticks there, esp since the pinhole is indicative of a larger cavity in the pipe. Will give it a try... – Eden Oct 17 '16 at 03:52
  • Ugh, that's too bad. I could understand them making you bring everything downstream from the repair up to code, but forcing you to bring bigger service into the house if you just need to replace a failing sewer pipe seems a little gratuitous, to me. Good luck! – Craig Tullis Oct 17 '16 at 21:23