Upon arrival find the gas valve for the water heater has failed. Checked millivolts on thermopile and reading 575, burner is clean. Travel to obtain necessary parts and return to replace defective gas valve and pilot assembly that came with new gas valve. Drained water heater, filled back up while doing gas connections. Checked all gas connections for leaks, went to all sinks and tubs and got as much air out of lines as possible. Told homeowner it will take at least 1-2 hours to get hot water back and maybe some air will spit water out. Homeowner is aware of all situations with water heater meaning time for water to get back, if they smell gas where to turn knob to off and air in lines.