Tank won't keep heating water

[bauer]

An A.O. Smith (FPSH 40 250) natural gas power vented water heater that is about 8 years old. Occassionally the water is only lukewarm and the unit only comes on for a few seconds. If water is drained from the tank and then refilled the unit will then heat water and work for about a month. Now that process only works for a day or two. Am I looking at a thermostat problem or something much bigger.

Thanks,

Jack

 

[Master Plumber Mark]

8 year old Smith...

Being a Smith says it all.....

it is most likely a thermostat problem, but with it being 8 years old, I would be hesitant to shell out the money for the new valve...

with that brand you are lucky to get 6 years out of it before it started leaking.....