How to repair a cast-iron waste pipe

Written by rachelle proulx
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How to repair a cast-iron waste pipe
Call a professional for major pipe repairs. (Jupiterimages/liquidlibrary/Getty Images)

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.

Skill level:

Things you need

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

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    Bad Smells or Water Leaking From Leaded Joints

  1. 1

    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.

  2. 2

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

  3. 3

    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.

    Holes in Cast-Iron Pipe

  1. 1

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

  2. 2

    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.

  3. 3

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

Tips and warnings

  • 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.

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