I have an State 50 gal natural gas water heater which is now producing inconsistently heated water. I believe that the water heater is not performing safely and needs to be repaired. It was installed by Bonney Plumbing in 06/06. What warrantee might be available to cover replacement of the temperature control portion of the water heater? I believe that even at 8 years of age, it is not worth replacing the water heater as an entire unit.