I have (had) the same model and it is probably due to calcium build up at the bottom. Water heaters need flushed occasionally (I think every other year). Anyway, NOTE: I had mine flushed one time about 4 years ago. Yesterday, the bottom went out and flooded part of the house. Mine was installed September 2001 - I see yours was installed in 2002. I would look into replacing it before it goes.

Fox,
You piggybacked on a two year old thread so I gave you your own.

Water heaters need flushed occasionally (I think every other year). Anyway, NOTE: I had mine flushed one time about 4 years ago. Yesterday,
You sahould flush your heater on a monthly basis. Otherwise, as you've found out, minerals can build up and eat away at the base of the tank.
Let me show you how to maintain your heater.


For long life and fewer troubles you should keep your heater clear of mineral build-up by FLUSHING NOT DRAINING on a regular schedule. Attach a hose to the boiler drain at the bottom of the tank. With the pressure on, open the boiler drain and let it run until the water runs clear. You will see a spurt of red,(rust) followed by white or yellow grains,(lime or calcium carbonate). This shouldn't take more then a few minutes. Do this monthly to keep it clear. Now flush out your hot water lines on ALL fixtures that are affected . Now pull each aerator and clean the screens. Be sure you put them back together the same way you took them out. Don't forget to flush it out every month. Your heater will thank you for it. The water heater in my house is over 55 tears old and came when the house was built. I have flushed it every month and only had to change a element in it one tine.
Hope this helps and thank you for rating my answer, Tom