Hot water heater not heating. Diagnose and find leaking gas control valve. 17 year old American water heater. Recommend replacement Rheem tank water heater, or Navien tankless water heater. Average water heater life span is 8-12 years old. Install new Navien tankless water heater with new pan and test for functionality. Recommend Gemline water softener to protect new water heater from hard water damage.