Q. We're working for a contractor who wants us to place a concrete pad, which will be a floor for a new home, on a base of crushed limestone. He's also planning to have copper water pipes coming up through the floor. Should we be concerned about a chemical reaction between the limestone and the copper pipe?
A. Copper should not react with the limestone or the concrete, provided it isn't too alkaline. Remember that hard water deposits that often occur in copper pipes are essentially made up of calcium carbonate, which is just like limestone.
However, PVC jacketing, or running the copper through a PVC sleeve, might be a good idea for a variety of reasons. Copper is relatively soft, and long-term exposure to sharp pieces of limestone may cut through the pipe and lead to leaks. Perhaps you can check into the gradation and sizing of the limestone pieces the builder plans to use.
Another thing to watch out for is keeping the copper pipe separated from any rebar or wire mesh. Galvanic corrosion might occur if those dissimilar metals were to come into contact.