DIYbanter - View Single Post - Cutting a 3" hole in cast-iron waste stack

wrote:

I'm looking to cut a 3" hole into a cast iron waste stack so that I
can attach a 3" PVC adapter to the waste stack in the basement.
I will then attach a separate 3" PVC riser (from the 2nd floor) to the
PVC adaper in the basement.

I'm wondering if anyone here has any similar cutting experience that
they'd be so kind as to impart.

The best advice I have so far is to drill a series of holes on the
circle that rpresents the new opening in the cast iron and then
connect the holes (scroll saw, sawzall, rotary cutting tool?).

Thanks for your consideration!

Al

Saddle fittings are not permitted. Also, the PVC saddle may not
conform to the radius of the CI pipe.

If you *must* do it this way, consider renting a hole saw the right
size.
Whether you swiss cheese the hole or saw it, there is the risk
of weakening the CI. That stack supports a *lot* of weight
all the way to the roof. A small fracture will propagate until
the section fails.

Jim