There are two types of water heaters: gas and electric. Although they have different heating methods, the heating element on both should be inspected and cleaned at least twice a year. The heater is located at the bottom of the tank and is activated whenever the temperature of the water in the tank drops below the desired temperature.
Gas Water Heater Cleaning
Start by visual inspecting the flame. It should be a blue color if it is operating at peak efficiency. An orange flame indicates that the burner is dirty. Turn the gas shutoff valve to off. Remove the access panel and vacuum all the dust. Use a wire brush to clean the ports of the burner and remove any rust. If you are not able to achieve a blue flame, call a professional for help.
Electric Water Heater Cleaning
Electric heating elements are more difficult to clean because the tank has to be emptied. First, turn off the power and close the water shutoff valve. Then attach a garden hose to the bottom valve and open to start draining out the water (i.e. turning on a hot water faucet in the house will speed up the process). Remove the access panel while the tank is draining.
After the tank is empty, remove the heating elements by unscrewing the bolts. Clean the scale off the element with a scouring pad and a solution of vinegar and water. Replace any elements that are starting to corrode. There are many different versions and models of electric heating elements, so take your old one to the hardware store to find a match. Corrosion will be a big problem if there isn't a water softener in your home.
After completing the maintenance ensure the drain valve is closed, but leave the one faucet open to let any air in the plumbing escape. Open the water supply while watching the elements for any leaks. After the tank has been filled, replace the access panel.