On Sep 27, 12:37�pm, HerHusband wrote:
I need to replace a short vertical section of cracked 4" cast iron
sewer line. �The section to be replaced is a little less than 4 feet
long. �The top of the cast iron above the connection is already
supported so it can't drop down when I take out the bad section.
What I am thinking of doing is breaking out the bad/cracked section of
cast iron, and hopefully ending up with a clean male end of the cast
iron at the top

I recently replaced cast iron pipes at my in-laws with PVC. I used a metal
cut-off wheel in my 4" angle grinder and it was quick and easy to make
clean cuts. Then I used a rubber "Fernco" style of coupling to connect the
new PVC to the existing cast iron.

In my case, the cast iron was 4" and the new PVC was 3", so I slid a long
length of PVC down the inside of the cast iron and used a reducing fernco
coupling. It worked great.

My question is about the bottom part. �I would like to insert the PVC
into the female cast iron fitting at the bottom and then seal that
connection with something.

If possible, I'd cut the female fitting away so you just have straight pipe
on each end you can connect with Fernco couplings.

I am thinking that since it is a vertical connection, and it is not
under pressure, this should be able to work without the fitting leaking..

Until you get a plugged sewer drain, or it otherwise backs up. Then that
connection would easily let waste flow out.

Is there some sealant or product that will work for this?

I think there are rubber fittings for adapting to female fittings, but I
haven't seen them locally. You would probably have to check with a plumbing
supply.

Good luck,

Anthony

be sure to support the cast iron above before removing the section to
be replace.

or the entire line may move, causing a rroof leak, cast iron is very
heavy