JTeller wrote:
Hi All,

Had a problem with the sewer system on the second floor.

Ended up opening up the wall on the first floor and had to cut out a
three-foot section of 4" cast iron sewer line. Sealed up the system
by installing a 3-foot section of 4" PVC (sch-40) using two 4" Fernco
rubbers.

I can't get the Ferncos to seal. The top Fernco weeps just enough to
show a moisture ring at the top. The bottom fernco has significant
leakage at the bottom. I tightened the clamps in stages with a
screwdriver and then switched to a ratchet with 1/4" bit. The Fernco
rubbers are simply not sealing on the cast iron.

Ugh. I'm at a loss. How can I seal this beast and still be able to
get access in the future???

One person wrote,

"My guess is that your corrosion crack
is extending past the point that you cut."

I think that may be a possibility, especially since you wrote, "The top
Fernco weeps just enough to show a moisture ring at the top". Seeing that
on the top connection seems unusual to me.

But, if it is not a cast iron pipe that is still cracked, the other thing
that I would try is to sand/grind the outside of the cast iron to make a
smoother surface for the Fernco to seal with, and also add 100% silicone
caulk in the connection between the Fernco and the cast iron to help it seal
better.