There is no hard-and-fast rule for regularly changing the water heater elements on a hot water tank. The accepted norm is that when the water heater is no longer heating, the element has burned out and needs to be replaced. However, as a whole, water heater elements can last for years and give solid performance.
An Element Gone Bad
The first sign that a water-heating element has gone bad is the lack of hot water or not enough hot water. Because most water heaters have two elements, one on top and one on the bottom, you may still have hot water if one goes bad but the quantity or temperature may be affected.
If your hot water quantity of is the same but the temperature isn't, the suspect is the top heating element. The top element boosts the water temperature to hot, but if the water is only warm, it has burned out.
If you get hot water but it only lasts for a few minutes, chances are the lower heating element is burned out. Cold water stays at the bottom of the tank, and therefore once the upper hot water runs out quickly, you'll get nothing but cold water.
Causes of Burned-Out Elements
Hard water deposits and water tank sludge are the major causes of element failure. Obviously, a water softener will increase element life, but just like a light bulb, eventually every element is going to burn out.
There are water heaters out there that swirl the water around, limiting sludge and hard water deposits. That technology will make your heating elements last longer but not forever.
Tools for the Job
You will need only a few basic tools for the job as well as a hose to drain the heater. Use a screwdriver to disconnect the electric leads going into the element, and a large socket or wrench that fits the actual head of the element. You also may need a pair of pliers to help pull the damaged or burned-out element from the tank.
Water heater elements are common and can be found at any hardware store.
Changing the Element
Before changing the element, always shut the power off for the heater by tripping the circuit breaker. This is an absolute must.
Then you will need to turn off the water feed line with a valve located next to the tank. Now you can drain the tank. An upper element replacement only needs to be drained below the element, but a lower element replacement means the tank has to be drained fully.
Remove the access panel covering the element that needs to be replaced. Unscrew the electrical wire leads to the element. Using your socket or wrench, unscrew the element from the water heater and pull it out. If it is badly damaged, you may need a pair of pliers to help with this.
Screw the new water element into the water heater, and make sure to use the new o-ring that came with it for a watertight seal. Tighten it firmly with your socket or pliers and screw on the electrical leads. Then replace the access panel.
This is very important. Turn the water valve on and allow the water tank to fill completely before flipping the water heater breaker to "on." If you do not do this, the elements will burn out immediately. You should have hot water in about a half an hour.