grant:—The one and only cause for an anode to be dissapated is DC electrical current. The higher voltage level present, the faster will be the consumption of the sacrifical anode. Normally a water heater anode has to deal with voltages in the millivolt range. There can be external forces at work in your particular case. If there is an improperly grounded appliance that has a solid state timer or control device that is impressing a DC charge into your Plumbing loop, efforts should be made to find it. When the anode is no longer available for the corrosion process to munch on, it will shift gears and develop a taste for Copper or other metal within that system. Check your premises for battery chargers(like those used for cell phones) and rechargeable cordless phones, or other DC producing devices or appliances, Most water heaters carry a 5-year warranty on the tank against failure. Contact the supplier for a possible adjustment. It is important to resolve this spurious voltage situation before you start to develop pin hole leaks in your copper piping. Lots of luck….Bud