Cast Iron Sewer Pipe question

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Quackingduck

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I have a cast iron sewer pipe under the house that the toilet feeds into, it drops a foot or two and then bends (elbow) and joins the main sewer vertical. I noticed yellow "scabs" and one wet-ish yellow deposit on the pipe and I'm wondering if it is rotting from the inside? I'm going to try to attach a couple pictures and I'm wondering if anyone else has ever seen anything like this. Also, whatever it is any suggestions for a repair? This is a huge pipe that runs under the house and I don't see replacing it end-to-end without MAJOR tear-out of the floor and some walls. I'm thinking cut the elbow and weld a new elbow into place?

Thank you in advance for any advice.Pipe 1.jpgPipe 1.jpgPipe 2.jpg
 
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Quackingduck

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Thanks for the advice. Does anyone have any idea what those yellow areas are? I don't think Flex couplings are feasible because the space is so tight - it the flex couplings A new elbow would just fit if it could be welded in. Is that feasible?
 

Sparky617

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Cast iron drain lines are not welded together. They are packed with a backing and then a solder can be poured into the joint to seal it. The yellow areas could be corrosion try taking a wire brush to them and see if you get down to metal. Probe the spots and see if there is solid metal below. The scale at the joints could be corrosion on the joints. Knock it off if you must. I suspect this is all pretty cosmetic and doesn't affect the function of the drain lines.
 

Quackingduck

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Thanks for the info Sparky. So if those old drain lines are just packed with something and soldered how would I get them apart? Heat the whole thing up with a propane torch? Is the packing something that would burn?

I'm kind of afraid to take a steel brush to that yellow stuff because if it is some kind of weird rot from inside I don't want to knock it off and make an actual hole. This is directly from the toilet remember.

Has anyone seen anything like this yellow stuff before? I should take a better picture of different parts. One patch looks kind of wet and fresh, almost like it is seeping from the inside. See how it looks like it is leaking over the galvanised strap? What on earth would react with cast iron in that way?
 

Quackingduck

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Can anyone think of a way to figure out what that yellow stuff is without risking a hole from chipping too much away? I don't have a gas spectrometer but if you do I can send you a bit for a test.
 

Jim_in_JAX_FLA

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first of all, to replace that, you need to worry about the vent line, that goes 10 or 12' UP, above there, through the ROOF....... you would need to either SUPPORT that, or cut it all out and replace with 4" PVC......as spanky said, unless it starts LEAKING, I would let it be......cast iron can and has lasted 100 years or more, if covered from rain, etc..... cast iron is generally only used UNDER houses, where it is kept away from moisture (on the OUTSIDE)......when it goes OUT FROM UNDER most houses, it changes to clay/ orangeburg/ pvc, something besides c.i.
......
 
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