How to Repair a Cast Iron Pipe Leak

Written by rachelle proulx
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How to Repair a Cast Iron Pipe Leak
Major repairs require a professional. (Jupiterimages/ Images)

Cast iron pipes last for a long time, but this does not mean they cannot become damaged and start to leak. Leaks are usually caused by corroding sections, often around the leaded joints. A do-it-yourselfer can repair small leaks in joints and small holes, but a professional should handle large leaks. Cast iron pipes need proper care and maintenance in order to last.

Skill level:
Moderately Challenging

Things you need

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

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    Leaking Joints

  1. 1

    Turn off the water supply to the pipe. Tap the joint lightly with a cold chisel and hammer. Cast iron pipe joints are soldered with lead; use a cold chisel to push the lead back into the joint.

  2. 2

    Clean the repair area by removing rust with a wire brush and dusting away debris with a clean rag.

  3. 3

    Fill the leaking area with a cast iron repair paste applied with a putty knife.

  4. 4

    Let the area dry before letting water or waste re-enter the pipe.


  1. 1

    Remove all rust and corrosion from the hole with a wire brush. Dust away debris with a clean rag.

  2. 2

    Apply plumber's epoxy around the hole so the patch is flush with the existing area, using a putty knife. Follow the manufacturer's instructions on how to mix the epoxy.

  3. 3

    Let the area dry before letting water or waste re-enter the pipe.

Tips and warnings

  • Do not disturb the pipe's supports. If the cast iron pipe supports are disturbed, the heavy pipe could fall down, injuring anyone in its way.
  • Call a professional to repair sections of pipe or large repairs.
  • Waste pipes contain toxic waste that can be hazardous to your health.

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