If the upper element burns out, the water heater will not work at all. The upper thermostat will never be satisfied, and power will not be switched to the lower element.
If the lower element has burnt out, it may still have some hot water, but it will run out quickly. The dip tube can also deteriorate and fail, allowing cold water to mix in the top portion of the tank. This cause you to not be able to use all of the hot water the tank has made.
In the mid to late 1990's there were a large quantity of water heaters that were constructed with defective dip tubes. Every other call for a plumber was a dip tube problem. This was an industry wide event, mostly resolved at this time.
Another problem with electric water heaters is scale build-up. Hard water scale deposits form at 169 degrees on the surface of the elements. This scale forms and makes the elements less efficient. The scale then falls off the elements and settles in the bottom of your tank. This scale, after time, flows through your pipes and clogs aerators and shower heads.
The scale also provides bacteria with a food source. Bacteria in the tank combined with the release of hydrogen from the zinc anode rod can form hydrogen sulfide, and a horrible rotten eggs smell. Sometimes replacement of the anode rod by your plumber can solve this. The preferred method is to have the plumber install a continuous chlorine feed, to the water heater feed. You will also want your plumber to install a post carbon filter to remove the excess chlorine.
Cahaba Valley Plumbing agrees with the manufacturer that your Electric Water Heater should be routinely flushed and drained by a qualified plumber.
A wealth of additional information about rotten egg smell/black water can be found at www.rheem.com.
Cahaba Valley Plumbing in Birmingham, AL, carries all needed parts for your residential or commercial Electric Water Heater.
The repair of an Electric Water Heater should always take into consideration the age of the existing unit. Will it be cost effective? Most water heaters only have a 6 year tank warranty. They typical lifespan is 10-15 years. We have, however, seen a few Rheem "Fury" units last over 36 years!
A 40 gallon Electric Water Heater currently costs less than $400. A rebuild kit with two elements and two thermostats currently costs less than $45.
The typical repair time for a qualified plumber to fix an Electric Water Heater varies from an hour to an hour and one half. The average replacement time is not much different, about two to three hours. Cahaba Valley Plumbing doesn't recommend repairing a water heater that is over 12 years old.
An Electric water heater typical to a single family home is powered by a 220/240 volts circuit. This circuit is protected by either a 25 or 30 amp breaker. During operation a typical 4500 watt element will draw 18 amperes. 18 amps are more than enough to kill you. Always call a professional plumber.
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The standard residential electric water control circuit consists of a manual reset high limit switch, an upper thermostat, lower thermostat, two heating elements and wires.
When power is turned on, the upper element is energized and heats the water in the upper third of the tank. When the upper third of the tank is heated to the temperature setting of the upper thermostat, power is switched to the lower heating element. The lower element continues to heat until the water in the lower portion of the tank reaches set temperature.
As hot water is drawn off of the top of the tank, the dip tube delivers cold water to the bottom of the tank. Eventually the cold water mixes with the hot, lowering the temperature to below the lower thermostat setting and the bottom element is energized. If enough water is drawn to cool the upper third of the tank, the upper thermostat will send poer to the upper thermostat first. When the upper third is heated, power will again be switched to the lower element.
Cahaba Valley Plumbing