I moved into a new house in August 2012 in Arizona, and quickly noticed air spurting from the showers and faucets when the hot water was turned on. When I turn the thermostat down on the hot water heater, the spurting air seems to be less. I contacted Bradford White, the hot water heater manufacturer and they advised it was either air in the lines or a faulty anode rod. The developer's plumber did come out in December and replaced the anode rod. The old anode rod was caked with mineral deposits. I have attached a picture. The plumber said he has seen ones like this but only in hot water heaters in service for several years. Could there be another explanation for the extreme amount of build-up? Is it possible the plumber initially installed an old heater in my new house, or is there something wrong with the water supply? I do have a water softener installed, and it is "city" water (not a well).