This type of rust usually isnt found until after a leak has happened and then its definately too late. A rod called an anode? (or sacrificial cathodic anode) is fitted in the water heater tank to prevent rust. As long as the anode is in good condition, degredation of the tank is reduced. Sadly it is not possible to see the condition of the anode by just looking at your water heater. You have to turn off the power and the water to the water heater and remove the anode with a wrench. Check the anode for deterioration at least twice a year; this will give you an idea of how long the anode will last. You can then include its replacement in your maintenance schedule accordingly. Crystal Palace Plumbers carry out this task. To stop the damage to the tank you can replace the anode, which takes about 40 minutes. Cathodic anodes are often not readily available in plumbing merchants so youll probably have to buy one from a dedicated supplier. As these anodes come in different shapes and sizes, be ready with the details of your system so that you get the right one. You can find this information on a label on the water-heater housing.To replace, follow these steps:1). Isolate the power to the heater and the cold water inlet valve on the top of the heater.2). Unscrew the hex bolt holding the cathodic anode in place and remove the old one or what remains.3). Install the new anode. A Crystal Palace Plumber can replace this.4). Fit the new piece in the reverse order that old one was removed. Be sure to use Teflon tape on the threaded fitting to prevent a leak.5). Turn the water and power to the water heater back on.