Hi, Rich. Your plumber and Lawnboy are exactly correct. You might look down the board to the problems that a poster has when he thought that he was just turning on and off the water to replace a water heater. Too much pressure popped the pressure relief valve on the water heater and made a mess in the basement.
Your plumber probably also mentioned a surge tank. Be sure that you get one installed when you have the pressure reducing valve installed. This is part of the solution and another way to prevent more and bigger problems in the future.