We'll call this the maintenance "5-minute" because you're probably going to invest more than a minute in draining your water heater-but the good news is that you don't have to drain it completely as your manual may suggest. Over time, any type of water heater tank will build up sediment- which has three harmful effects on your home's hot water system. First, the sediment takes up space which effectively makes your water heater smaller. Second, the sediment can insulate the bottom of the tank and in a gas water heater, where much of the flame's heat is absorbed into the water, or even cover a lower element in an electric water heater causing a reduction in heating efficiency. Third, the sediment scratches the glass lining of the water heater tank, resulting in exposed metal - which leads to rust and eventual tank failure.
You can extend the life of the tank and increase the efficiency of the system by simply draining a couple gallons of water off the bottom of the tank. First, shut the unit down by turning the gas valve to "pilot" or "off", or flipping off the breaker for electric units. Second, turn off the cold water supply line, usually located on the right side as you face the unit. Attach a garden hose to the drain valve on the water heater tank, and run it to a drain. Turn on a hot water faucet somewhere in your home to allow the water to flow and then open the drain valve toward the bottom of the tank. Check the color of the water that drains- at first it may appear dark, but after just a few gallons it will become clear. At that point you can close the drain and turn off the hot water faucet you had turned on previously. Turn the cold water supply back on and turn the power or gas supply back on and you're done!
The next time you turn on a hot water faucet there may be a couple air pockets so don't worry if you hear a bit of noise.
Certified Home Inspector.