Hello, I have a house with hot water heating. I had a heating company come by and they said that one of my zonal valves is faulty or had a problem because I can't control the heat in 3 rooms (it has a mind of its own), whereas the rest of the house is temperature contrrolled by thermostat. The heating guy could not locate the valves as the house is about 30 years old. I have no idea where they are... does anyone know how to loacte the zonal valves... or do I have to start cutting into my drywall? I do not have plans for the house and the city where I live does not either. Help?

Usually valves are exposed and by law if not exposed that have to have a access door and the door must be labeled. The control circuit for the zone valve will have wires going to it. Follow the wires if you can.