If your hot water is not working properly, the cause of this may be as simple as a bad heating element in your electric water heater. Electric water heaters have two heating elements - an upper one and a lower one. The upper heating element is made up of a series of metal loops that have been electrically charged, causing them to heat up. The lower heating element is the main powerhouse behind the electric water heating system, heating up the cold water that enters the hot water tank at the bottom of the heater. The upper heating element simply raises the already hot water temperature further by heating the top portion of water in the tank.
Step 1 - Diagnose the Problem
If you still have hot water available but it runs out more quickly, this usually means that the lower heating element has failed, causing only the top of the water to get hot. As the cold water rises from the unheated bottom of the tank, your hot water supply fails. On the other hand, if you are still getting the same amount of hot water, but it no longer gets as hot as it used to, this usually means that the upper heating element has failed. The lower element is forced to heat the whole tank, which drastically reduces the overall temperature of your water. Whether you suspect the lower or upper element to be a problem, be on the safe side and check both.
Step 2 - Test Heater
Disconnect the heater from its power source. Make sure the water in the heater is room temperature or below before you begin your inspection. There should be two panels on your water heater, an upper and lower. Remove the upper access panel screws first on the electric water heater with a screwdriver. Remove the insulation and disconnect the electrical wire at the terminal and use your multimeter to test the electrical flow. If the meter needle does not move or remains at "infinity," the heating element is no longer working and needs to be replaced. If you get a clear reading on the meter or some movement, the element is fine and you can move on to testing the other element, the insulation, and reinstall the access panel. Repeat this process on the lower heating element.
Step 3 - Check Resistance
Using your multimeter, set meter to the RX1 setting to check resistance. Touch the probes to each of your terminal screws. If there is any resistance reading at all, then the element is working fine. If you don't get any movement in your reading, the heating element will need to be replaced.