Expansion tank and water heater had a slight pinhole leak in it. After discussing several options with customer, he decided replacement of water heater was the best option to go with as it was going on 10 yrs old. Drained down existing water heater disconnected the gas, flue piping and water piping then removed it. Installed new Rheem water heater. Connected flue, gas and water piping to new heater. Filled the tank and bled air from water and gas piping to test for leaks, tested OK. Lit pilot and set temperature knob to “hot” setting, approximately 120°.