Electric water heaters have two heating elements, both which are immersed inside the tank. To access these two elements, a person must first remove the two access panels on the front of the tank. Gas water heaters do not have elements but heat with a burner.
With electric water heaters, the lower element is the most common cause of problems. Sediment and minerals are more likely to affect this element and it usually burns out before the top element. It is possible to test the elements without removing them by using an ohmmeter. If the resistance reads infinity, the element requires replacement.
Homeowners who plan to replace the heating element should turn off the power to the tank and drain the water first. Some units use a screw-in element, while others use an element with a flange. Removing the screw-in element is easier with a special tool available at most home improvement stores. Removing the four screws from the flange releases this type of element.
Both types of replacements should supply a replacement rubber gasket. Installing the new gasket helps to prevent water leaks. Once the element is tightened by hand in place, it is tightened further using tools to avoid water leaks. The installer must fill the tank with water before turning on the power, or the new element burns out quickly.