I am hoping that some of the knowledgeable people on this group can
answer some questions regarding older cast iron drain stacks. Some months
ago our insurance was non-renewed because the insurance company refuses to
insure homes with cast iron in them. The reason given for this rule is that
they "rot out from within and burst", we weren't even covered for sewer
backup/breakout under that policy anyways. Fast forward to now, we have a
new insurance company (a farm mutual), and their inspector didn't even note
the cast iron drains even though he knew that was why the other company had
Right now we are in the middle of renovations, and incidentally the
that contain the stack are being re-cladded with drywall and as thus the
stack is currently fully exposed from basement to attic. If we were to
replace the cast iron with ABS, now would be the time to do it however I
doubt this is a task I could do myself. I imagine the cast iron is heavy
(even if half of it has rotted away) and well... it would not be a pleasant
job. I have received a quote to replace it (materials+labour) for about
So the question has become, is it worth replacing? Is it really going
to spring a leak someday? Is it going to 'burst' like the first insurance
company said, or will it start as a slow leak and progress?
Some details: The total vertical section of the pipe is about 2 stories
plus attic, the pipe becomes horizontal at the basement ceiling and runs for
about 15' until it drops down about a foot to the cast iron sewer that goes
out to the septic tank. The pipe is probably about 50+ years old.
Thanks in advance
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I would not replace with anything other than cast iron. It is long
lasting and quiet.
As for the rot from the inside out, sure, but then so do almost all
pipes. Even if that were not so, most pipes are buried in walls so you
could not see the outside anyway. That theory just does not hold water.
Now you are talking about 50 year old stuff. It may have another 30+
years life, but since you now have it exposed and it is that old, I would
consider having it replaced, but I would keep with the cast iron. Once
replaced, you will never need to worry about it in your life time.
firstname.lastname@example.org (WasteNotWantNot) wrote in
Even when they happen, cast iron vertical stack failures are not generally
catastrophic. Usually you notice a sewer-gas smell, and on invsetigation,
you find a small corroded hole. Or you have a leak, call a plumber, and he
finds a section with paper thin walls. Fixing it might be expensive, but
usually not overly complicated, unless your wast plumbing is exceptionally
It might be worth contacting your state insurance regulatory office and see
what they have to say about this.
We went through this a few years ago. I had the wall open for another
project in the upstairs bathroom and discovered that the cast iron
stack had rusted through. No leaks since the hole was above the
topmost drain entrance. The stack was about 75 years old at that
point. We had it replaced with cast iron -- I think the quietness is
a major advantage over the plastic. I will say, if you go with cast
iron, call around for some quotes. Our quotes varied by almost a
factor of ten. We had the stack replaced from basement floor to roof
To save money and effort, our plumber used plastic above the topmost
drain. There it is just a vent, and water noise is not an issue.
Also, that is where it rotted out before; I suspect increased air
exchange near the top of the vent leads to faster rusting. So I expect
the new stack to last even longer than the old one. HOpefully the
rest of the house will last that long!
So, if you have the dough, I would say this might be a good time to
replace the stack. I would advise going with cast iron; you take
your peace and quiet for granted now, but in other people's houses
with plastic pipes, when they are sitting quietly in the kitchen and
someone flushes upstairs, they hear it gurgling all the way down. If
you have drywall rather than lath and plaster that is less soundproof
On the other hand, the current pipe might last quite a few more years.
I agree with the other posters it is not prone to any sort of sudden
catastrophic failure. And if it needs replacing later, so you would
have to open up the walls (maybe part of the ceiling) then patch the
drywall and re-paint afterward. That's not really such a big deal and
you might be able to do some or all of it yourself if you are so
I just had an upstairs BR redone on a 70 year old home. I was prepared
to pay the plumber to rip out all the old cast iron stack and replace
but when we looked at it the inside of the stack was as clean as the day
it was installed. The plumber was pretty shocked that it looked so good.
one problem he often saw is that people will ground electrical onto the
iron water line which can speed corrosion.
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