I have a waterfurnace geo unit & an ao smith 65 gal h2o heater with a water softener. the anode rods only seem to last about 18 months. anyone have any thoughts why the rods have such a short life? in my 60+ years on this earth I've never had to replace an anode rod before.

Is the water softener new and is it piped upstream to the water heater.

the geo, h2o heater, & softener were all put in-service appx 4 years ago. the water is softened before entering the h2o heater.

You can switch to a less reactive rod - like aluminum.

The water softener is altering the chemistry of the water and by doing so is the primary cause of the anode rods being destroyed.

Sorry to hijack the thread, but speaking of anode rods. Is one necessary in the preheat tank? I'm using my old propane water heater (gutted and stuffed w/ insulation) as my buffer tank and I'm sure the original anode rod is long gone. Do I need to replace it?

Denyh: Adding a water softener greatly changes the water chemistry. Certian parts of the country have dedicated services for anode replacement every 1-1/2 to 2 years because of incredibly hard wate and related softening issues. Plus, please remember, the tank walls have decreased in thickness over the last 30-40 years. If you have no problem with H2S, I would stay away from Aluminum rods. They are less reactive which means that they protect the tank less. I'd rather replace the rod every 18 months then replace the tank every 36 months!

Khonderd: It's always a good idea to use an anode whenever you have a steel tank and potable water. If you are using the tank as a buffer, then yes... new anode.

You can get impressed current anodes if you don't like replacing rods.