The following applies to electric water heaters only. The heating elements in an electric water heater are susceptible to sediment buildup, burnout and sudden failure. Learn how to clean and inspect the heating elements in your electric water heater.
- Most electric water heaters will have two heating elements: one in the upper half of the water heater and one in the lower half. These two horizontal elements look similar to the metal grill pieces on older electric stovetops. As the name implies, the heating elements literally heat the water in the water heater. The elements are attached into compartments on the side of the tank. The compartments are behind panels with screws holding the panel in place. Elements can either be high-watt or low-watt. High-watt elements are smaller and burn hotter while the lower-watt has about twice as much surface area, but it will not be nearly as hot as a high-watt element. The lower element does most of the work with the upper element running only when there is a large amount of new cold water inside the water heater. Both elements rarely come on at the same time.
- Thermostats on water heaters usually work for several years without any problems. You will find a thermostat attached to the heating element compartment on the side of the water heater for the lower heating element; the upper element usually does not have a thermostat. The upper element is preset for 120° F and will automatically shut off if it ever reaches 190° F to prevent the circuit from overheating (see How To Operate Electric and Gas Water Heater Temperature Controls). If this happens, there is a red reset button near the bottom heating element compartment.
- If you only have one heating element, it will be attached to the lower half of the water heater and it will perform like the upper element described in the previous paragraph.
- Sediment build-up. Sediment build-up occurs slowly over several years. In electric water heaters, a bad sulfur odor is indicative of this problem. The lower heating element burning out is also a sign of sediment build-up. Sediment can encase the element, causing it to fail, although this is rare. Usually, sediment will flake off the element naturally and build up at the bottom of the water heater. However, sometimes sediment inside the water heater can pile up so high that it completely covers the lower heating element in a mass of what looks like hard snow. If this happens, the hot water in your showers will run out twice as fast.
The speed of sediment build-up also depends on the kind of heating element installed in your water heater. Between the two types of heating elements, high-watt and low-watt, the low-watt element is far superior. Because low-watt elements have twice the surface area as high-watt elements, they can burn at a lower temperature and still heat water in the water heater in the same amount of time. And low-watt elements produce far less sediment. If you ever need to replace a bad element, make sure to replace it with a low-watt element. Please note that while high-watt elements almost never become encrusted, low-watt elements can become encrusted with sediment.
- Before doing any work with your water heater, remember to first turn off the power. The elements will be either bolted or screwed in to the side of the water heater tank. Whether bolted or screwed in, the elements will also use a rubber or plastic water gasket to prevent leaks. You should replace the gasket whenever you remove the element for cleaning, especially if the old gasket has hardened. Also, if the heat element is screwed in, wrap the threads of the screw with Teflon tape. To clean the elements, use a toothbrush and some vinegar to scrub the coils.
- Another reason an element will burn out is galvanic corrosion. Galvanic corrosion usually causes the joint to rust between the copper sheath of the electrical element and where it touches the steel tank. The anode rod inside the water heater should prevent this problem. However, if you replace the elements and it only lasts a few months, then it may not be the heating element but rather the anode rod that is causing the problem (See How To Install, Inspect and Evaluate Anode Rods in Water Heaters.)