The photo below shows a venting stack that was disconnected. The stack runs from the basement to the attic and out through the roof. Which means it's perfect to pull new water, gas, and vent lines up through it. It was probably part of a gravity furnace that was replaced at some point.

What kind of pipe is this? And what's the most effective way of cutting it out?

My guess is that it's clay in my circa 1935 home.

Big Fat Pipe

2 Answers 2


It is fired clay. It has metal bands to hold it in place.

  • You can try and take it out a piece at a time, starting from the top.
  • However, if the "grout" between them is strong then you just smash it, as long as you can do it safely. Again, start from the top and smash one segment at a time.
  • Also known as "terracotta" and locally is mostly found in the ground doing stormwater. The external ribs are not a feature I've ever seen - perhaps that's related to using them vertically as opposed to buried horizontally.
    – Criggie
    Commented Mar 4 at 20:54
  • Top down. Got it. There's a round about suggestion that maybe we just put the new risers inside of it, and save the hassle of busting it out?
    – MFMauceri
    Commented Mar 4 at 21:24
  • 1
    @MFMauceri Yes, top down is the key bit. You don't want to smash the bottom-most piece only to discover that half of the straps holding the stack in place have loosened over the ages and are now unable to carry the whole thing, so that half a ton of fired clay is now coming down to meet you. That's the sort of approach which can earn you at least a honourable mention at the Darwin Awards. :-)
    – TooTea
    Commented Mar 5 at 13:13

Just to clarify, you want to gain access to the interior of the pipe so that you can use it as a conduit for various other services, not remove the pipe and use the resulting void? Note that either way you are creating a convenient way for fire to move through the home. That may need to be addressed.

An angle grinder would be suitable for cutting out sections of the pipe wall for access. Leaving part of the pipe circumference would provide support for the rest of the pipe length.

A hole saw would make tidier holes if you are awarding style points.

Before doing anything else you want to be absolutely sure that you know every connection to the pipe and have plans to plug things appropriately. Finding out later that someone tied in a condensate drain or stack vent would be a nuisance.

  • Hmmm. Initially I just wanted to cut it out and fill the "void" with new risers (H2O, drain, CSST gas) I didn't plan on putting the new lines in the existing pipe, but that might not be the worst idea in the world. And yes, will definitely seal off at every floor level.
    – MFMauceri
    Commented Mar 4 at 21:21
  • 2
    @MFMauceri When I read "Which means it's perfect to pull new water, gas, and vent lines up through it." it seemed like you wanted to stay within the pipe, hence the question.
    – HABO
    Commented Mar 4 at 21:22
  • Depending on how much cutting's required, I may just do that!
    – MFMauceri
    Commented Mar 5 at 3:21
  • +1 for a hole saw. Wetting the blade/ceramic should make cutting faster, cleaner, and less dusty.
    – JimmyJames
    Commented Mar 5 at 16:35

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