Had a plumber come out to investigate why there was leakage and bad smells coming into basement from an interior cinderblock wall in my basement. It was discovered that the sink/dishwasher drain (cast iron) that spans the full length of the slab floor and through this cinderblock wall to the main sewer line in the basement was leaking. The leak flows more when water is run in the sink. I was told the best thing to do was to abandon this drain, cut the slab, and lay a new line. I was quoted $3400. Since I am about to start a total gut job kitchen remodel, this is an expense I am not prepared to have. I had planned on doing the work myself, but have a crazy idea that I would like to run past everyone. Along with the drain pipe there is a hot and cold supply as well as a 4" duct which provides heat to a register located in the toekick right below the sink cabinet.
My idea is to abandon the old drain pipe but instead of cutting the slab and replacing it I would like to abandon the use of the heat duct and simply run the new 2" drain pipe through the 4" duct. The second part of the question is should I do the same with the two water supply lines? The reason I ask is what happens if they have leaks as well or if not now then maybe at some point in the future. The problem I think I might have if I did run the new supply lines through as well is would I have noisy pipes since they would not be secured along this 12 foot span.