Cleaning off buried cast iron pipe?

[woodrail]

Last night I began the repair of a sanitary line in a basement. The 4" cast iron main stack has rotted out right at the floor line.

I cut out the floor and discovered the stack has actual broken at a joint. Looks like I'm replacing about 6 feet with PVC.

The existing cast iron I'm connecting into is probably 80+ years old. It is surround by mostly clay like material. This clay is almost rock hard, cemented to the cast iron. As I need it cleaned to get a solid connection to the pvc, all the soil all needs removed.

I've lightly taken a hammer to it, but that's not working to good an I'm concerned I'll break right thru the cast.

Any suggestion? Torch? Grinder? Acid?

 

[Tronyadorable]

Wire wheel.Soap and water. Then hydrochloric. Then wire wheel again. NO HITTING !

Don't use any chlorox type **** near hydrochloric. Trust me on that

 

[buffalobill]

air hammer with extreme caution?

 

[Tronyadorable]

Make a draw knife and scrape it. NO hitting.No vibration.
If it's truly a clay boiling water might help.

 

[BD1]

I cleaned and repaired the same using a END GRINDER and a flapper disc and wire wheel. You could use a 4 1/2'' disc grinder and wire wheel but maybe difficult getting in their.
I have a Milwaukee , here's the HF model, http://www.harborfreight.com/electric-die-grinder-with-long-shaft-44141.html

 

[woodrail]

I'm liking the end grinder idea. It's a bonus because it gives me an excuse to buy a new tool!

thanks.

 

[rweaver]

+1 for end grinder but it doesn't need to be perfect. make sure you use a fernco fitting (full rubber two bands) instead of a no-hub connector. From years of experience with underground plumbing a small weeper will silt up around pipe and stop.

 

[G_P]

Cup brush on an angle grinder. DO NOT HIT THE PIPE unless you want it to break. Cast iron is strong but brittle.

 

[Lippyp]

If it's just clay/soil then how about just making a pit around the area to be cleaned, line it with some plastic sheet to minimise leakage and fill it with water for a while, should soften the deposits enough to just be able to scrub them off with a stiff brush, you could use a pressure washer, messy but will help, then it's just a quick clean-up of any rust/scale.