Replacing section of cast iron pipe with PVC? Learn how

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Here is how to go about replacing a section of cast iron pipe with PVC

If you have cast iron pipes in your house- they’re still in use in some homes despite PVC overtaking them in popularity- you may want to replace a small section that’s troubled.

For instance, you may have a pipe that is leaking persistently due to corrosion and you have resolved to remove the bad segment and fix a PVC piece in its place (perhaps pending an overhaul).

Now, adapting cast iron pipe to PVC is no mean feat and you may struggle to complete the repair if you don’t know how to connect PVC to cast iron piping.

Below we teach you how to go about replacing section of cast iron pipe with PVC to help mend the messy spot.

Replacing section of cast iron pipe with PVC – step by step guide

We shall break the steps into several parts to make it easy for you to follow the procedure…

Replacing section of cast iron pipe with PVC: Part 1 – cutting out the troublesome pipe length

The first thing is to cut out the length of the cast iron pipe to be replaced.

Cutting cast iron is, of course, no walk in the park- we all know that the metal is extremely tough.

The good news is you can still slice through it with the right tool.

So, what is the best way to cut through the material?

Well, you have a couple of tools to choose from…

  1. A snap cutter– cast iron brittle nature can be manipulated using a snap cutter until its cuts through cast iron pipes.
  2. Recip saw- a reciprocal saw (sawzall) outfitted with a quality diamond blade (marked cast iron cutting) also saws the metal in no time.
  3. Handheld power tools – appliances such as an angle grinder can do the job too as long as you add the correct disc (metal cutting disc) or diamond wheel.

Here is how to cut cast iron pipe with each tool:

 Snap cutter

  • Mark where you’ll be cutting on the pipe– both ends- using chalk. Draw straight lines around the circumference at each point.
  • To use the snap cutter, first position the chain around the pipe (in a loop) so that more wheels (maximum possible) are in contact with the cast iron pipe.
  • Pressurize the ratchet arm now. This tightens the chain and will in turn force the cutting disks to penetrate the pipe.

Tip: For a quality cut, be sure to apply even pressure all around the pipe.

  • Score the pipe (if necessary) several times before applying the final pressure to have the pipe finally break into two.
  • Repeat the process on the remaining end.

Recip saw

A reciprocating saw could be your best bet if you’re working in a cramped location (it’s a nimble gadget).

It’s simple to use as well.


  • Mark the cut lines with chalk as explained earlier.
  • Now turn on the saw.
  • Slowly and gently saw through the marked spots until the pipe snaps.

An angle grinder

  • Start by marking the start and end of the chunk to be cut with chalk.
  • Fire up your grinder and begin cutting. Initially, make a groove by working your way all around the pipe so as to weaken it.
  • Now continue ‘grinding’ around the pipework while letting the wheel to pierce through the same point until the pipe breaks.

Tip: Before cutting the pipe, ensure that the plumbing stack (or run) is secured in place by wrapping material such as rebar tie wire above the part you’ll be cutting.

You may use screws or even nails to secure the ends of the wire to the closest joist or a header board.

If you happen to be operating on a vertically positioned pipe, the best idea is to use riser clamps for support (Follow manufacturer instructions to get the installation right).

Note: There are other alternatives that cut cast iron including soil pipe cutters. Use what is readily available at home or from neighbors.

Replacing section of cast iron pipe with PVC: Part 2 – introducing the replacement PVC pipe


  • Buy rightly-sized Fernco no hub couplings (or any other good brand) from your nearest home improvement store or online to help you connect cast iron to PVC. These have the least work and are preferred by plumbers for such cast iron pipe replacement jobs.
  • Measure and cut a length of PVC pipe, long enough to fit as a replacement.
  • Clean the area where you’ll be inserting the PVC pipe. You can wipe rust with your wire brush and dust away other debris with a rag.
  • Lastly, smooth down the edges of your cast iron pipes (sand it down).

Step by step:

  • Slip the coupling connectors on the new PVC pipe and adjust them to position.
  • Lift the PVC pipe and fit the first ‘coupled’ edge into one end of the CI pipe. The other edge obviously goes to the remaining end.
  • Again adjust the coupling until satisfied they have held onto the cast iron pipe on either end properly.
  • Now tighten the couplings (hold the PVC pipe as you do this) until you feel some resistance.
  • That’s all. Proceed to test the freshly installed connection for leakage.

Final note

We hope that this has answered all your questions about replacing section of cast iron pipe with PVC.

Remember to wear protective gear when working with tools such as grinders – the last thing you want is to suffer an injury in the middle of the job.

It’s also important to dispose off the iron cast pipe cutting safely at the end of the process.

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