Replacing Old Metal Drainage Pipes

Old and corroded cast iron pipeHave your old cast iron or galvanized drain pipes worn out? Well replacing them with more modern plastic pipes is actually quite simple for the do it yourselfer. Although cast iron pipes are very durable and known to be quieter when water is flowing through them, they are quite difficult to work with and will cost a great deal more than their plastic equivalents.

Tools and materials

  • Angle grinder with metal cutting discs
  • Reciprocating saw with long metal blade
  • Hacksaw for plastic pipe
  • Mechanical joint fittings
  • Glue and primer for the plastic pipe your using
  • Measuring tape

*Make sure you wear safety goggles and are familiar with the tools you will need to use.

Removing the old drainage pipes

  • Make a mental note or better yet a sketch of how the current piping arrangement is before gutting all of the drain lines.
  • If your only planning to replace a small section you must secure the other sections of the drain to keep them in place. Cast iron pipe is heavy and the top section of the pipe may not be properly supported, this could cause it to drop, and you don't want that.
  • Don't cut the pipe off at the floor leave a foot or so to attach a mechanical coupling. This will also give you some leeway if the pipe decides to crack.
  • Start cutting the old cast iron drains from the highest point and work downward. Take your time and make straight cuts.
  • If after cutting the pipe you discover the drain is completely worn out you will either have to cut to a new section and hope that it's better or start think about a complete gutting of the current DWV(Drain waste and vent).

Replacing the drainage with ABS / PVC

  • Connections between the old cast iron or galvanized drain and the new plastic pipes are made with mechanical couplings. MJ - Mechanical Joint Connecting cast iron to ABS pipe using a mechanical joint
  • The mechanical joint can be placed over one end of the pipe and the rubber rolled down (remove the metal sleeve first) so the new pipe can be inserted. Then roll the rubber over the new section of pipe and clamp the metal sleeve down.
  • Cut new sections of plastic pipe and glue fittings in place as necessary.
  • Replace any pipe hangers that were supporting the pipe or add new ones and go have a frosty beverage.