I have to cut off a section of cast iron waste pipe in my attic to tie
in a vent .My concern is when I cut off the section of pipe, the
weight of the upper part of pipe would cause it to possible come
loose from the roof flashing and sink, thus causing a roof leak. The
last thing I want to do is open up a can of worms by doing this job. I
was wondering if I should be concerned or if anyone else has done a
job like this, what advice to offer. Thanks
I would fabricate a permanent support for the upper section.
Heavy steel strap clamp around it tied up to rafters.
If you put turnbuckles in the tie section you can preload it
If you can get on the roof to work, much better to simply
replace the section with PVC and a new rubber flashing boot.
I like Jim's idea, but I also think that even the slightest movement of the
pipe could affect the integrity of the seal around the flashing. You'd still
want to get up there with the appropriate caulk when the job's done.
On Thu, 20 Sep 2007 08:34:26 -0700, Mikepier wrote:
You didn't state exactly where you are working on the vent pipe. Chances
are you will see very little, if any, movement if you work below existing
vents tied into the main pipe. It would still be a wise choice to secure
the uppermost part of the pipe with strap supports designed to hold pipes
A reciprocating saw would seem to move the pipe less than doing so with a
I did exactly what you are doing several years back. That vent was cast
iron. I had to cut the pipe in the basement to reroute tub and stool.
There were enough pipes above me to support the vent without moving.
Reflashing or caulking the existing flash when done makes sense.
If all you are doing is adding a vent, you can buy strap around
devices. Then cut a square hole in the cast pipe with an angle
grinder and attach the "strap on". You dont need to cut the whole
pipe. After all, it's only a vent.
Possibly..... There are some plumbing supply stores online. However,
I'd check your local plumbing supply places. These things are
commonly used. I dont know the exact name for them, but I have seen
them. It's basically just a device that fits around the cast iron
pipe. It fits around about half the pipe, has a rubber gasket, and
uses large hose clamps to attach it. There will be a 1.5 or 2 inch
threaded hole in the side to attach your pipe. They also make similar
devices for water pipes, so it's easier to attach a water source to an
ice maker. Those are called "saddle valves", but they have an actual
valve built in. Knowing that, these drain pipe devices could be
called "saddle" (something). Just a guess.
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