tapping into 4" cast iron stack

[Ivan Vegvary]

Is there another way to tap a vent into a cast iron stack other than cutting out a chunk and installing a fitting? Last time I did this (over 20 years ago) the stack above the cut came down like a guillotine. After all they do 'live taps' on high pressure water mains all the time. Vent is 1.5 inch abs. 4" c.i. stack is only 3 feet away. Presently the vent runs 22 feet horizontally before exiting the building then vertically up through the roof eave. Thanks for any help. Ivan Vegvary

[hrhofmann]

Plumbers strap to support the pipe above the cut, and two sleeves, one at t op and one at bottom of new pipe with the tap on the side. Only choices ar e the angle of the new incoming pipe. You can get a right angle input or o ne at perhaps 45 degrees downsloping (unless you put it in upside down)

[Retired plumber]

If it is a vent only, and not a drain, here is the easy way to do it:

Obtain a 4x1.5" abs saddle "Y" fitting. (A saddle fitting is sliced lengthwise and clamped to an existing pipe. You can modify a normal 4x1.5.)

Drill several 1/4" holes (inside a 1" circle) in cast iron using masonary bit.

Apply silicone or roofing sealer to fitting and clamp saddle fitting onto cast iron, making sure the holes line up to the 1.5" opening. You need a airtight seal to avoid potential sewer gas leakage.

Connect new vent.

Probably not up to code, but definitely will work.

[clare]

Might be a good time to replace that CI stack with plastic - before it rusts through and leaks. Getting hard to get insurance (new policy) on a house with ci stack OR galvanized water piping.(here in Ontario Canada)

[Ed Pawlowski]

There are fittings that clamp onto the pipe and you drill out a hole with a hole saw. Check out saddle fittings

[Nate Nagel]

If you can find a "saddle tee" to fit, that will work as well e.g.

but keep in mind that you'll still have to drill a hole in the stack to fit your pipe... doesn't sound like a fun job (but then again, neither is cutting the pipe.) Different hazards though, I get nervous when drilling anything larger than a 1/2" hole with a hand drill although saws are safer than bits. Had my wrists wrenched/smashed too many times, this is definitely a job for a drill motor with a T-handle.

If you do end up cutting, look into bracing the upper section of the pipe with a riser clamp somehow before firing up the Sawzall or chain cutter.

nate