Q: We've been asked to place a concrete pad as the floor for a newhome, on a base of crushed limestone. There will be copper water pipescoming up through the floor. Are there any reasons for concern about a chemical reaction between the limestone and the copper pipe?

A: Copper is unlikely to react with the limestone or concrete, as long as it isn't too alkaline. The hard water deposits that sometimes build up in copper pipes are made up mostly of calcium carbonate, just like limestone. However, it might still be a good idea to run the copper through a PVC sleeve. Copper is relatively soft, so long-term exposure to sharp pieces of limestone could cut through the pipe and lead to leaks, depending on the gradation and sizing of the crushed limestone the builder plans to use.

You also will want to keep the copper pipe away from any rebar or wire mesh. Galvanic corrosion can occur when those dissimilar metals come into contact.