I have a Reliance 501 model 530 gas water heater in a mobile home that we moved from the country into town. It is set for LP and we need to switch it to Nat gas. Detailed directions for changing it over are listed on the side of the heater, but we cannot find the orifices that they refer to. We had heat/air guy over to change the gas range and furnace over but he said he wasn't allowed to change the water heater. When the heater was installed 8 years ago the installer changed it from Nat to LP but he is no longer around. Any suggestions appreciated. By the way, this heater is specifically designed for mobile homes. Thankyou, Ted