Most water-heater tanks are made of glass-lined steel. If water gets through imperfections in the glass, then you can count on rust and eventually a leak. But because the tank has no inspection ports, it’s hard to tell when it’s dirty or beginning to rust. Actually, tank rust usually isn’t discovered until after a leak occurs — and then it’s too late. You’re not totally without recourse, though.
A special rod called a cathodic anode (or sacrificial anode) is built in to the water-heater tank assembly to prevent rust. As long as the rod is in good condition, deterioration of the tank is drastically reduced.
Unfortunately, you can’t determine 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.
To prevent damage to the tank, simply replace the cathodic anode, a $15 item that takes about 30 minutes to install. Cathodic anodes are often not readily available in hardware stores — you’ll probably have to buy one from a plumbing-supply company. Because anodes come in all shapes and sizes, be prepared to give them the make and model of your water heater so that you get the right one. You can find this information on a label on the water-heater housing.
To replace the cathodic anode, follow these steps:
Turn off the power to the water heater and the cold-water inlet valve at the top of the water heater.
Unscrew the hex bolt holding the cathodic anode in place and remove the rod — or what remains of it.
You may discover that only a short piece of rusted metal rod remains — definitely a sign that a new anode is desperately needed.
The cathodic anode is about 3 to 5 feet long, about 3/4 inch in diameter, and has a hex bolt welded onto one end. The hex bolt screws into the top of the tank, holding the rod in place inside the tank, and, when tightened down, the nut also makes a watertight seal at the same time.
Install the new anode.
Insert the new anode in the reverse order that the previous one was removed. Be sure to use Teflon tape on the threaded fitting to prevent a leak.
Turn the water and power to the water heater back on.
Most factory-installed anodes are magnesium, which can produce a sulfite-reducing bacteria that makes your water smell like rotten eggs. Using a replacement anode made of zinc or aluminum will prevent this problem. Peeeww!
