Most Pressure Reduction Valves (PRV’s) will make a high pitched noise when water is flowing through it. If you are trying to locate a buried PRV, first turn on a hose bibb to start water flow. Next, listen to pipes near the meter using a large screw driver, crow bar or other metal object to your ear. If you hear a high pitch “hiss”, you will likely have a buried PRV there. Back-flow devices will make the same noise so if one is nearby feeding an irrigation line it would be good to turn it off while listening for the PRV.