Replaced the AO Smith with a GE/Rheem, same size, capacity. Install was easy. Double checked all the fittings (used Sharkbite WH fittings for the first time) and venting. Filled tank, turned on pilot, held for 1 minute, released and the pilot would not remain lit. Tried again (1+ minute) and again (2 plus minute) and still the pilot would not remain on. So pulled the burner assembly (4 TORX screws), examined the thermocouple/pilot relationship, all seemed correctly spaced. Reinstalled burner assembly, still the pilot would not remain lit. Goggled the symptoms (check thermocouple)... then detached the thermocouple from the gas valve, attached multimeter, turned on pilot (held down) and voltage did not climb (as expected). Back to HD, purchased $12 thermocouple. Installed in 10 minutes, fired up pilot and.. pilot remained on. Burner cycles correctly and no issues over 36 hour period. New WH, go figure.