8 year old natural gas unit has been reliable until recently when the pilot light expires without any externally identifiable reason. These facts apply: No changes to the surrounding environment (doors into the room the same, no ventilation changes, no new gas appliances in use) The thermocouple produces 24mv and the connection is clean where it screws into the gas valve. The pilot will hold after 6 seconds of heating and may go a whole day without issue. I pulled the pilot and thermocouple assembly and cleaned them good. No obvious damage. I blew out gas line with HP air to the extent possible through that tiny hole. I verified that while the furnace is running a few feet away that the hot water heater exhaust still draws smoke up the exhaust piping very strongly. Unit has never had any water damage due to flooding, backed up pipes, etc. The burner unit fins show some signs of cracking at the ends but I would not say they are bad and there was not a lot of debris on the bottom of the unit. The photos show the heater specs and the gas control valve specs. The wife unit is tired of cold morning showers and may replace the husband unit if not fixed soon. The student is ready to learn at the feet of the master.