How to repair a cast-iron waste pipe

Updated July 20, 2017

Older homes often have cast-iron waste pipes, which can last for decades. Over time, cast-iron pipes can rust through, causing holes, leaking joints or crumbling sections. Repairing small holes or leaking joints is a simple DIY project, but if a section of the cast-iron waste pipe needs to be replaced, then you'll need to call a professional, who will cut out the damaged pipe and replace it with a PVC pipe.

Gently tap the lead back into the joint with a cold chisel and hammer. Be careful when you're tapping not to tap too hard, or further damage could occur.

Brush away any rust or corrosion from around the joint with a wire brush and a rag.

Apply cast-iron repair paste to the area with a putty knife until the damaged area is filled. Let the cast-iron repair paste dry to the manufacturer's recommendations before you use the pipe.

Clean the area around the hole with a wire brush and a rag until all the rust is removed.

Mix two-part plumber's epoxy to the manufacturer's instructions. Press the two-part plumber's epoxy over the hole and mould it to the cast-iron pipe.

Let the two-part plumber's epoxy dry to the manufacturer's specifications before you use the pipe.


Do not disturb the cast-iron pipe's support clamps, or the heavy pipe could come crashing down. Waste is toxic; have a professional repair sections of pipe and any large holes.

Things You'll Need

  • Cold chisel
  • Hammer
  • Wire brush
  • Rag
  • Cast-iron repair paste
  • Putty knife
  • Two-part plumber's epoxy
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About the Author

Rachelle Proulx has been writing since 2000. She co-owns a pet-sitting company, providing her the experience to cover pet care and small business. Proulx is also a flooring specialist who writes about flooring options, preparation, application and maintenance.