Need advice to repair basement toilet drain

[grk200703]

Greetings!

I have a house built around 1967 that requires a basement toilet drain repair. Plumbing is not my line of work, but I think I can do the job if I can get some advice here.

I have removed the toilet to expose a 7" dia steel flange flush with tile on concrete slab, attached by lead to an approximately 5" od iron pipe (3.75" id). The iron pipe immediately elbows beneath the floor slab and runs straight at least 5' toward where the main drain routes from the house to the street. Would it likely turn down into the main drain?

The iron pipe appears to have failed at the elbow where it begins its run under the slab. A few 0.25" dia roots have entered there and appear to taper off farther down the pipe. Ants have entered and since the toilet was seldom used, were able to import a lot of soil both up and down the pipe.

I have shop-vac'ed out soil as far as I can reach. The root entry seems confined to near the elbow. I speculate that soil was carried down the pipe by ants. They also carried it up into the toilet hollows.

All other plumbing in the house is working, so I figure this problem extends only as far as the ants carried soil down the dormant drain.

My plan is to remove the slab above the pipe, remove a few feet of failed iron piping, finish shop-vac'ing out the remaining soil without just pushing soil on toward the main drain, replace the bad piping with PVC?, patch the slab and tile, and install the toilet.

Sound like a good plan?
o How to remove the concrete slab and how wide to remove?
o How to cut iron pipe confined in trench?
o How to attach new PVC to old iron? Rubber and straps? PVC parts list?
o Gravel back fill material?
o Other tips?

Thanks for considering my problem! The house is a tear down so this is not a long term repair.

Glenn

[jadnashua]

There are a couple of ways to cut the CI: a snap cutter (you can rent one at most places - looks like a large, weird bicycle chain with a rachet to tighten it up), a grinder, or a saw. By far, the fastest is the snap cutter. You'll need enough room around the pipe to use the tools. Underground, you can use the rubber sleeve with hose clamps. Make sure to backfill carefully so the pipe ends are well supported and stay aligned.

If the pipe is cracked, you may want to go to where it meets the main line. If you do, then you'd need a different method to fix it....Fernco makes special rubber dognuts that fit into the hub and then the pvc is a compression fit inside of it. Problem is, not all pipes are the same, and the local shops may not carry the exact size you need. Alternative is to cut that part off and replace with pvc, or get a plumber to relead in a new piece. If the CI is solid, you don't need to cut back that far, and this is a mute point.

Problem is, you won't know until you dig it up the condition of the pipe or fittings. On a good day, it is farily easy, on a bad one, you could be replacing a lot more than you think now.