Archive for Monday, June 10, 2013


Fix-It Chick: Replace a cast-iron pipe

June 10, 2013


Replacing a section of cast iron pipe is easier than you think.

Step 1: Cast-iron pipe is very heavy. Before cutting out a section of pipe, secure the plumbing stack or run in place. Wrap rebar tie wire or metal pipe strap above the section of pipe to be cut. Use nails or screws to secure each end of the wire or strap to a nearby joist or header board.

When securing a vertical stack, wrap the wire or strap below a hub or an elbowed section of the pipe to keep the pipe from slipping down.

Cast-iron plumbing

Cast-iron plumbing

Step 2: A reciprocating saw with a carbide blade or an angle grinder with a diamond blade will both cut cast-iron pipe, as will a chisel and a hammer. A ratcheting soil pipe cutter is by far the easiest tool to use to cut through cast-iron pipe. Soil pipe cutters can be rented from your local hardware store or rental center.

Step 3: Read the manufacturer’s instructions completely before using the soil pipe cutter.

Step 4: Choose a smooth section of the pipe to cut, preferably 4 inches or more from any hub or joint. Make sure the pipe is free of dirt and debris. Use a stiff wire brush to remove any loose rust.

Step 5: Wrap the cutting chain around the pipe and lock the chain into place per the manufacturer’s instructions.

Step 6: Once the chain is secure and the cutter’s knobs are adjusted properly, use a slow and steady motion to ratchet the chain tight around the cast-iron pipe. As the chain is tightened, the cutting wheels will squeeze into the pipe and the pipe will snap beneath the pressure.

Step 7: Remove as large of a section of the old pipe as possible and replace it with a similar sized piece of PVC pipe.

Step 8: Use rubber couplings with adjustable metal clamps to attach the new section of PVC pipe to each open end of the cast-iron pipe. Fernco makes rubber couplings in several sizes to fit just about any situation. Rubbing a few drops of dish soap on the inside of the couplings will make them slide onto the pipe easier.

Step 9: Once the couplings are in place, tighten the metal clamps. Put away your tools and move on to your next project


Tgill 4 years, 11 months ago

This will only work if you have good pipe left to attach couplings to. If you are using soil pipe cutters on old cast iron you may very well fracture it and end replacing a lot more pipe then you had planned to Just be careful

5thgeneration 4 years, 11 months ago

Having done this professionally for the last 24 years, I would never trust bailing wire to support the weight of a cast iron stack. If you're cutting out a piece of 2" cast on a short horizontal run, sure, go for it. If you think that bailing wire will support 300+ lbs of cast iron, plus the added weight of the lead that is caulking every joint together on a 4" soil stack, you're going to be in for a big surprise. There is a lot of preparation that goes into supporting the weight of a vertical stack before you cut a section out from it, even more so when you're replacing the bottom of the stack, and it goes out 2 or more stories to the roof. I usually try not to get involved in the comments on these articles, and I fully support the D.I.Y. mentality, but this installment is lacking some very crucial info, including the answer to "How in the heck to I get the piece of cast iron that I just cut with a chain cutter out of the stack?" It isn't that easy, folks.

Peaty Romano 4 years, 11 months ago

I have to agree with everything you said. My dad was a master plumber and I worked with him for years. Back when we use to install this type of pipe, tucking in oakum and pouring the lead. These pipes are deceptively heavy, even small sections.

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