Repairing (Splicing) Malleable Iron Pipes

Many old houses still have some malleable (cast)  iron pipes. Many years ago, 4-inch drainpipes were used to attach the house drain system to the main sewer line or septic system. These lines are extremely durable and can last a hundred years if the ground does not shift. Although the pipe is slowly eroding, most people have a bigger problem with buildup in the line. The use of chemical drain cleaner is very harsh on metal pipes and the cause of may failures.  These chemicals do not react with plastics but can literally eat metal pipes.

When these pipes fail ( and I don't recommend replacing them unless they fail), it is simple task to replace or splice plastic pipe into the effected area.

Malleable Iron pipes are extremely heavy and can easily crush an arm or a leg (or crack your skull) if they fall from their mounts. Be careful when removing any old pipes.

1. Use a metal-cutting abrasive blade on your circular saw (or grinder) and cut all the way around the old pipe.  This will generate a huge amount of sparks to make sure the surrounding area is free of any combustible material.
2. Cut a section of Schedule 40 PVC to length.
3. Slide a rubber coupler over the PVC. Use the thickest rubber you can find and make sure it has stainless steel clamps.
4. Install the PVC and slide the rubber coupler over the cast iron pipe.
5. Tighten the band clamps
6. Glue the other end of the PVC pipe to the rest of the system .

Hopefully your splice joint is not in direct sunlight as this can reduce the life of the rubber. I installed one 10 years ago and it is still holding but it won't be long before it needs to be replaced again.

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