I have to add a 2 inch line to an existing underground 4" buried cast iron soil pipe. I can follow the shielded coupling of a PVC wye. My question is, how do you clean up the lumpy cast iron pipe so that the perfectly round and smooth coupling actually makes a sealable joint?

Hi Peking...

You use a hammer and chisel and work your way around the pipe. You start with a cold chisel and hammer and kind of knock the tough stuff off without cracking the pipe...

Then you work your way up to and including a 1/2 way decent wood chisel until you have cleaned the entire pipe surface back to about a 3" or more depth.

As you can imagine... the bottom part of the pipe is the most difficult. Here, to really clean the bottom half of the pipe with a particularly hard clay type soil, for example, you will need to dig a hole that is 3-4 inches deeper than the pipe so that you can actually angle the chisel at the pipe as you hit the hard soil off the pipe with the chisel (using hammer)... that make sense? Safety goggles must be worn here!

You can also use an ANGLE GRINDER... ;) Again, you need to be sure to wear safety goggles and be careful of flying dirt/small rocks. This will definitely remove the majority of the dirt on the top of the pipe. The bottom part of the pipe would require an even deeper hole than the hammer/chisel method to work an angle grinder.

You may also be able to use one of those flexible PVC cable saws... see image... just pull back and forth. Just another option.

Anyway, depending on the soil type this can be quite difficult!

I hope your soil is softer than most of the soil I have run into... :)

MARK
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Thanks buddy. I ought to send you a picture of my Philly soil. Gray clay that has been keeping water near the pipe for 70 years due to POS foundation drainage. Soil is like glue when wet, but not particularly resistant to chiseling. I don't know if the lumps are soil or rust or combo. We'll see. I got a grinder and a hundred ways to do it. Thanks.

Good luck with it! Let me know how you made out... :)

MARK