Replacing electric water heater elements is a fairly easy task that can often restore an old malfunctioning water heater that has been running out of hot water to its full output potential. Of course you should properly troubleshoot the water heater and make sure that the element(s) have gone bad, and that the bad elements are the only problem before replacing them. You should also consider the condition of the water heater before replacing the elements. If the water heater is older than 12 years old it is probably better to replace the water heater or, if there is signs of leakage and corrosion replacement is advised.
Testing Water Heater Elements
Testing the elements will require a screwdriver or, nut-driver to open the access panel on the side of the water heater, and a multi-meter to measure the resistance of the element. Before doing anything you must shut off the electrical power to the water heater to avoid the chance of electrical shock and avoid damage to the multi-meter. Remove the upper access panel first and measure the voltage across the L1 & L2 terminals on the upper thermostat, which should measure 0 volts to verify the power has been turned off. Also measure voltage from each terminal to ground to ensure that both legs of the 2-pole breaker have turned off. Disconnect the wires from the element terminals then measure the resistance across the element terminals. The resistance typically measures between 10 – 15 ohms depending on the wattage and voltage of the element. The electrical formulas watts / voltage = current in amps, and voltage / amps = resistance in ohms, can be used to determine what the measurement should be if desired, but typically the numbers given will suffice. If the measurement is lower the element has shorted, if it measures infinite the element is open, either case requires replacement. Next measure resistance from each terminal on the element to ground, which should measure open or, infinite. If there is a measurable resistance then the element has shorted to ground and should be replaced. An element shorted to ground can cause the water in the water heater to continue to heat even after the thermostat has shut off due to only one leg of the supplied voltage being controlled by the thermostat, tripping the red eco button on the upper thermostat. On the lower element open the access panel, remove the wires from the terminal screws and repeat the measuring process.
Selecting A Water Heater Element
An important step in replacing the water heater element(s) is selecting the right element for your water heater. While most residential water heaters will be supplied from a 30 amp circuit breaker with 10 gauge wire there are circumstances such as some mobile homes where a smaller 20 amp circuit breaker and 12 gauge wire is used. You should avoid increasing the wattage of the elements used to avoid the possibility of creating an overloaded electrical circuit and the danger of a fire associated with it. Wattage upgrades should only be done after thoroughly inspecting the electrical supply and making sure that any increase is in full compliance with the electrical code. Decreasing the wattage while there is no safety risk will result in a slower recovery rate and many times disappointment in the water heaters performance.
Another important part in selecting the right element is the material the element is made from and the wattage density of the element. The economy elements are often made of metals which may corrode over time and fail, the best elements are made of Incoloy which is a high grade of stainless steel which is very corrosion resistant and will last a long time. Watt density is another factor to consider, the watt density does not affect the amount of hot water produced as the same amount of energy is placed into the water but the term is used to describe the amount of wattage used in each inch of the element. The higher the watt density the hotter the element is, and the higher the density more susceptible to burning out they are. High watt density elements have 150 and higher watts per square inch of element surface and are typically found in the single loop and fold back style elements. Medium watt density elements have between 100 – 150 watts per square inch of element surface and typically are fold back style elements. Low watt density elements have 75+ watts per square inch of element surface and are typically fold back or, fold back ripple style elements. Ultra-Low watt density elements have 50+ watts per square inch of element surface and are typically fold back and fold back ripple style elements.
The ultra-low watt density elements are the least susceptible to burning out with some manufacturers claiming they will not burn out when covered in lime deposits from hard water precipitating to the bottom of the water heater. Many also claim that they will also not burn out when they are dry fired which would ruin a high watt density element in seconds. I would not recommend testing the accuracy of these claims but I do recommend this type as being the best possible choice for a water heater element. It is important to realize that despite the element operating cooler that the amount of water heated is still the same, each square inch of the element is doing less heating but there are more square inches to do the work. The Camco Premium Lime Life Elements, and the Reliance 9000405-045 4500 Water Heater Element are both examples of this type of element.
Replacing Water Heater Elements
To replace the element in addition to the tools above you will in most cases need a 1 1/2” six point socket and a breaker bar to unscrew the element. There is a stamped six point socket commonly sold in home centers and supply houses as water heater element sockets, but these typically do not work very well, and often slip off the nut rounding it off in the process. Make sure the electrical power is turned off, then shut off the water supply to the water heater, open a hot water faucet that is located above the water heater in the home to break the vacuum and allow the water heater to drain. If you have a place that you can drain the water heater to that is below the level of the water heater all you will need is a garden hose connected to the water heater drain running to the safe drainage point and it will drain by gravity. If the only place you can drain the water heater to is above the water heater then you will need a pump with garden hose connections on the inlet and outlet of the pump to pump the water up and out of the water heater. Some pros will change the elements on the fly with the water heater full and without a hot faucet open using the suction to keep the water in the water heater, this can be done, but it also can get very messy if all doesn’t go well. I would recommend using the safe method for the DIYer.
Once the water has been drained from the water heater, put the socket and breaker bar on the element nut and turn it counterclockwise to unscrew the element. Once the element has unscrewed it should pull straight out of the hole, but sometimes the fold back and fold back ripple styles can be difficult to remove especially if the failure of the element has caused the element to unfold. This can result in a prying, and pulling match that sometimes even results in having to cut off the element and letting it fall to the bottom of the tank. If you run into this situation you will be glad you drained the water out of the tank. When replacing the lower element I like to attempt to remove as much of the lime buildup as possible from the bottom of the tank. I use a piece of 3/4” PEX tubing attached to my wet/dry vac hose to remove it and it works well.
You are then ready to place the new water heater element into the water heater. Make sure the rubber gasket is in place before screwing it in. Staring the threads is a little difficult because of the weight of the element, be sure to hold the element nut square to the hole in the water heater and it should thread almost all the way in using just your fingers. Then finish with snugging the element in place with the breaker bar. Once the element has been tightened you can then connect the wires to the screw terminals and then secure the access cover in place.
Turning The Water Heater Back On
After the element(s) have been replaced and the access covers are secured you the next step is to refill the water heater with water. I like to shut off the hot faucet and leave the water heater drain open to flush any of the remaining lime out of the bottom of the tank, then turn on the water supply to the water heater allowing it to flush until clear. Once the water is draining clear you should close the drain and reopen the hot faucet until the air is expelled from the tank and only water is coming out of the faucet. This will signal the tank is full and you are then ready to turn on the electrical power to the water heater. You should start seeing warm water in about 15 minutes and the tank should run completely through its heating cycle in about an hour.
This article has covered only replacing the elements. As a plumbing pro I would like to note that when repairing an electric water heater there is a cost for a plumber to respond to a plumbing call, and drain down the water heater. This cost makes it prudent for the plumber to troubleshoot the water heater and find what is wrong with it down to the individual part, but in most cases replace both thermostats and both elements at the time of service, allowing full confidence in the guarantee, and a satisfied customer. The components of the water heater are very much like the headlights on your care, when one burns out the other one will follow shortly. My recommendation is for the DIYer to follow the same approach, troubleshooting the water heater to make sure that the parts you are installing will fix the problem, then going with all new parts to ensure reliability.