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Cast Iron Plumbing Stack

cast iron plumbing stack

Cast Iron Plumbing Stack | Here's a 4-inch no-hub cast iron plumbing stack that branches off to two different full bathrooms. I installed this in a Bar Harbor home in 2019. Copyright 2019 Tim Carter

"A cast iron plumbing stack is a thing of beauty, especially if it's the sleek newer no-hub cast iron." Tim Carter - Founder, AsktheBuilder.com

Cast Iron Plumbing Stack - Quiet and Strong

Cast iron plumbing is still available and it's better than ever. The wall thickness of a cast iron plumbing stack is now consistent with modern spun-casting manufacturing methods.

You can have a plumber install a cast iron plumbing stack in your home. Here are a few benefits:

  • cast iron is quiet - you'll not hear water rushing down a wall or across a ceiling
  • cast iron is fireproof - PVC creates a toxic deadly gas when it burns
  • cast iron is immune from leaks caused by errant carpentry nails
cast iron plumbing stack

This is a first-class cast iron plumbing installation. Modern no-hub cast iron is being used. Copyright 2019 Tim Carter

How Are the Joints Sealed?

Modern no-hub cast iron relies on ingenious no-hub couplings that combine a durable rubber collar with a full-size stainless-steel band clamp. When the two bolts on the band clamp are tightened to around 60 pounds of torque, they squeeze the rubber against the outer walls of the cast iron creating a water and gas leak-proof joint.

Watch this video to see these no-hub clamps:

How is Cast Iron Supported?

Vertical cast iron plumbing stacks transfer the weight to the floor using a simple riser clamp. The clamp tightens around the pipe and the strong metal legs spread out the weight onto the nearby floor.

riser clamp

This is a riser clamp. When you tighten the two large bolts, it grabs onto the cast iron pipe like an eagle's talons grip a large tasty 8-pound bass it just scooped from Long Pond in Acadia National Park. Copyright 2019 Tim Carter

Horizontal runs of cast iron pipe are supported by clevis hangers that cradle the pipe. A threaded rod with washers and nuts on each end areĀ used to connect the hangers to the ceiling above.

You can also rest cast iron pipe on strong wood blocking if it runs through floor trusses as you see in this photo:

cast iron plumbing stack

This cast iron stack is going to collect all the waste and drain water from a master bedroom in my daughter's home. Copyright 2019 Tim Carter

How Do You Cut Cast Iron?

I cut cast iron pipe using an electric cutoff saw equipped with a special carbide blade.

cut cast iron

This is a special carbide blade that fits into a standard chop saw. It cuts right through cast iron. The red arrow points to the small chunks of carbide. CLICK or TAP HERE or the image to have this blade delivered to your home.

Is Cast Iron Expensive?

Cast iron is more expensive than the modern foam-core PVC pipe. It's important to realize you don't have to install cast iron throughout your home. Each vertical cast iron plumbing stack that has toilet water in it can be cast iron as well as and horizontal 3-inch pipes in ceilings.

All other plumbing drain, waste, and vent lines can be PVC.

How Does PVC Connect to Cast Iron?

You use simple PVC no-hub adapters to transition between cast iron and PVC pipe.

cast iron plumbing stack

This cast iron is so beautiful the plumber (me) is trying to convince the homeowner of using clear plexiglass as the ceiling so all can see it forever. Copyright 2019 Tim Carter

Cast Iron Plumbing Stack - Quiet and Durable | AsktheBuilder.com
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Cast Iron Plumbing Stack - Quiet and Durable | AsktheBuilder.com
A cast iron plumbing stack is what you want in your home. It's quiet, durable, and fireproof.
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9 Responses to Cast Iron Plumbing Stack

  1. I would like to see the riser clamp you mentioned that has legs to distribute the weight to the frame members or floor. Very interesting as I thought cast iron was obsoleted long ago by PVC.

  2. Hi Tim,
    Love your site and the email newsletters, have purchased from Amazon some of your recommendations and never been disappointed. Our son, an avid outdoorsman, loves the small firestarter you suggested! I call that a 'cheap thrill'.

    Anyhow, liking the videos of your daughter's new home. A question, re. the cast iron piping, of which I'm also a big fan. Some of the pics show a large U-shaped run, which (I can't see all of it tho') looks like it could have gone straight across thru the trusses to reach its final destination. Why is that? Just curious.

    • You can only cross the trusses at certain locations to have the needed height so you don't touch any of the angled support members of the truss.

      You also need room to make the transitions off the 3-inch horizontal branch. Some fitting combinations take up more space than you'd imagine, especially the sweep 90s (L bends) under the toilets.

  3. Any concern about gases coming through the stack that will one day be a bathroom in the attic? Would you periodically add water to the trap or is there an effective cap that will prevent gases from coming through?

    I love the idea of plumbing for the future. I was a teenager when my dad had me dig across our driveway and bury a couple of pieces of PVC before new concrete was poured. I asked why and he said just you never know. 35 years later when the city brought in a new waterline on the wrong side of the drive that PVC came in very handy.

    • The stacks that are to be used in the future are capped off with an approved cap. They come for both cast iron and PVC. Do NOT use the rubber test caps and do NOT depend on the thin ABS wafer plastic also used for tests. You MUST use a cap that has the same wall thickness as the pipe.

  4. Hi Tim,
    I'm very glad I found your site. The information you give is priceless. I was just wondering why you would use old cast Iron & not white PVC, When I went to your writing & was fascinated in the explanation & pictures. Great Job. I'm 65 now & not doing the major rebuilding of my home I've done for 40+ yrs. But I wish I had come upon your site many years ago. Plaese keep it going. I've just begun to read all the past advice. THANKS TIM

  5. Hi Tim, As a retired water works operator I also find pipes and ways to do fascinating. Thanks for the time to take and post. Stay in the flow, sara

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