The lowest estimate we received on laying a new service line from utility water main to the house had one item of disagreement. My husband says there should be sand both over and under pex pipe when laid into a trench. My husband thinks it should be standard (SOP), this plumber says he has never done it that way. This "lowest estimate is based upon using this trench method. He plans to make the trench 12-18" deep. Can you bring the two sides together or do I need to choose another plumbing contractor?