I have a 10 year old Hot Water Heater, it is installed in my 2nd Home. It has had power applied to it maybe 2 weeks per year. The water, I know is very stale and needs to be flushed each year. The HW Heater is on city water in South Carolina. Is the rotten egg smell a sign that the anode or tank should be replaced? Other than the egg smell it heats and runs good.