Occasionally it becomes necessary to repair cast iron pipe due to rust or other damage. Cast iron pipes often rust along the bottom of the pipe, where water accumulates and pools. Cast iron was typically used in older homes while newer homes generally have PVC piping.
Repairing and replacing damaged cast iron pipe is a very simple process, although the weight of cast iron pipes can make removing the damaged sections unwieldy and cumbersome. However, once the repair is made with PVC pipe, it should last a very long time. Connect the two sections together using rubber gaskets that are also called no hub bands. These bands require only the tightening of a connector nut and squeeze the two pipe sections together. Reinforce the connection with pipe fixative applied to both the PVC repair and the remaining existing cast iron pipe.
Step 1 – Determine Where Damage Is Located
Determine where the pipe is still solid by running your hand along the bottom of the pipe, since this is usually where the rust is located. Look closely at the pipe, looking for a marked difference between the damaged pipe and pipe that is not damaged. Use a pencil to mark where the pipe is damaged and where the damage ends. Measure the amount of pipe that needs to be replaced.
Step 2 – Turn Off Water and Drain Pipe
Turn off the water to the pipe and run any remaining water through the pipe to clear as much water out of it as possible.
Step 3 – Cut Pipe
Attach a diamond tip cutting blade to the reciprocating saw. Cut the pipe in two. If there is water inside the pipe, be careful not to allow the water to run back into the saw.
Step 4 – Cut Other End of Pipe/Remove Pipe
Locate the other end of the pipe where the pipe is still good, and cut that end of the pipe. Pull the damaged pipe out.
Step 5 – Cut PVC for Replacement
Cut a section of PVC pipe that is the same size as the damaged cast iron pipe. Join the two sections together, using couplings to connect the two pipe sections.
Step 6 – Fit PVC in Place
Place PVC cleaner on all of the joints. Allow the cleaner to dry. Apply joint glue to both fittings and attach together, twisting slightly.
Step 7 – Connect Gasket
Connect a no hub band gasket where the PVC meets the cast iron. Use a ¼ nut driver to tighten the band into place. A no hub band gasket is a rubber connecter with stainless steel bands around the outside of the connector and has stainless clamps.
Step 8 – Turn Water Back on and Test
Turn on the pipe's water supply. Check your work by running the water through the pipe for several minutes. Stop the water and carefully run your hand along where the pipe sections meet, feeling for leaks or seeping dampness. If you discover problems, turn the water off and retighten the no hub bank gaskets.