Thank you for the very valuable information. I have read through those pages and learned even more. Here is my situation – This heater is in a rental property in Charlotte, North Carolina while I live in California. So I need to select a water heater remotely and won’t have the serial number of the unit in time to order specific anodes.
I spoke to State Industries customer service and was told they need the serial number before giving me a part number for magnesium anode to order. Their heater model GS6-50-BCT seemed close to what I have now.
I checked specifications on A.O. Smith G9-T5040NV and G12-UT5040NV sold by Lowe’s. Even the 12 year warranty model does not have Magnesium anode. The specs also indicate their inside coating is ceramic (not glass) and I’m not sure if that makes any difference.
Would you need serial numbers to identify the correct anode rods for these models?