Understanding Construction Costs

How To Fix Damaged Cast Iron Pipes

If you live in an older home, it likely has cast iron pipes. Cast iron pipes are prone to punctures and rust. Rust is obvious, but a whole won't be noticed until you start smelling sewage.

However, you usually don't have to replace the whole pipe. While underground pipes require a professional, you should be able to fix cast iron pipes below the subfloor by following these steps:

Prepare to Fix the Pipe

To fix cast iron piping, gather:

  • work gloves
  • safety glasses
  • flashlight
  • tape measure
  • carpenter's pencil or chalk
  • wire brush
  • steel putty knife
  • utility knife
  • nut driver
  • pliers rubber-sleeve clamp with nut
  • reciprocating saw and diamond metal blade 
  • PVC glue 
  • PVC cleaner
  • PVC pipe 
  • no-hub band gasket
  • cast iron patch compound (optional)

Look for cast iron pipes by accessing the subfloor from the crawl space a basement. A pipe with a hole will commonly leak a puddle. Feel along the pipe to determine rust, which may not be obvious. A pipe with a soft feel usually has rust, and you may need to loosen some blistering paint to find rust.

Fix a Hole

Shut off the water supply from the main valve, which is usually close to your water meter. To fix a small rust hole, use a steel putty knife to scrape rust, and smooth it with a wire brush. Apply enough compound around the pipe with the putty knife to seal the hole. 

Detach the nut using the nut driver, open the clamp, and insert it into the repair area. Use the pliers to press the clamp tabs, and tighten the bolt.

Repair a Rusted Section

Mark the damaged area to cut on the pipe with chalk or pencil. Before you cut, it is ideal to plug the saw into a GFCI outlet that will intercept short to prevent shock from water in the pipe. Cut the damaged section of pipe with the saw while an assistant holds the other end.  

Use a rag and a PVC cleaner to clean the new PVC fittings, and let them dry. Measure the size of the damaged space, mark them on the pipe, and cut the pipe to fit, and cut burrs with a utility knife.

Join the pipe to the fittings getting your helper to hold the opposite end, and attach the no-hub band, a connector that has stainless steel bands, and tighten it using the nut driver. Test the fittings for proper tightness, and dab glue on the fittings to secure, and let it dry.

Contact a plumbing contractor for more information and assistance.