If the hot water in your house isn't as hot as it used to be, then you should be suspicious of a heating element failure in the water heater. The electrical elements in your water heater are in continual contact with the water, and this makes them susceptible to failure from electrolytic reactions with the natural calcium contaminants in your household water.
Here are some tips for diagnosing a failed hot water heater element to assist you in determining if this is the problem with your home's hot water supply:
Feel the Outside of the Water Tank
Your hot water heater has an upper and a lower heating element. The heating elements are connected to the outside of the tank and sit inside of the water where they convert electricity into heat and warm the water. Water heaters have too much water inside of them for a single element, so you will see one located near the top and another near the bottom of the tank. The elements look like a large bolt who's head sticks out of the side of the tank.
To determine if a heating element is the cause of the problem, you can rub your hand along the side of the tank. If one-half of the tank is hotter than the other, then you know that its corresponding heating element is not working properly.
Try Resetting the Power Breaker Before Replacing a Failed Element
Sometimes the electronics in a water heater's element simply need to be restarted, just as you would reboot your computer. Before you drain your water heater to replace its elements, first check the power panel and reset the breaker connected to the water heater's electrical supply. If the breaker is tripped, then this is the problem with your hot water, but even if it is not tripped, the electrical connection can still be an issue. Turn off the breaker and then turn it back on. Wait a few minutes and feel the water heater again to see if the problem is solved.
For the Best Results Replace Both Elements at the Same Time
Finally, as long as you are going through all of the work to drain your water heater to replace an element, you should replace both of them. The reason is that they were both made at the same time and have the same approximate useful lifespan. If you do not replace both elements, then you will likely find yourself having to repeat the process in the next year or two. Elements are inexpensive items and it is always advised for you to replace both at the same time.