Electric Water Heaters
Typical storage type electric water heater showing the various components.
TPR Valve
The TPR valve (Temperature Pressure Relief) or T&P valve, is a safety device that releases water if the pressure or temperature reach unsafe levels. There is a manual release lever located on the valve. TPR valves should be periodically tested by lifting the manual release lever at least once a year.
Due to the scalding potential of the discharge from the TPR valve, the outlet from the valve should be piped to a safe area. Typically they are piped down to within 6 inches of the floor or even outside of the dwelling at near ground level. Check with your local building department for local building code requirements.
Anode
The sacrificial anode is a metal rod usually magnesium or aluminum which helps prevent corrosion of the water heater tank. Electrolysis eats away the anode (hence the word sacrificial) instead of the steel of the tank. Once the anode is gone the tank itself begins to corrode. The anode is screwed into the top of the water heater and can be replaced. Sometimes the anode is built into a special hot water outlet fitting. Softened water can cause the anode to wear out more quickly.
Dip Tube
The dip tube directs incoming cold water to the bottom of the water heater tank, preventing pre-mature mixing of incoming cold water with the out going hot water. Without the dip tube it may be difficult to get hot water even when the tank is full of hot water.
Sometimes the dip tube is curved at the bottom causing a swirling motion in the bottom of the water heater to reduce sediment buildup, or making it easier to remove the sediment through the drain valve.
NOTE: SACRAMENTO, CA — The state Department of Consumer Affairs is warning residents that a little-known device in their home water heaters may be faulty, causing damage to heaters and plumbing, including point-of-use water treatment equipment. The water-heater dip tube delivers cold water from an external water source to the bottom of the heater. Perfection Corp. of Madison, OH, manufacturer of virtually all dip tubes used in the United States, produced an unknown number of defective tubes between 1993 and 1996. These tubes can decompose, sending tiny particles of plastic and sludge through the plumbing system. This in turn can clog the faucet aerators and screens causing low water pressure at the fixtures. For more dip tube information check the following two sites:
Thermostat
The thermostat senses when the water temperature drops below a certain temperature and causes the electric heating elements to come on and heat the water. When the hot water in the water heater reaches the desired temperature the thermostat shuts off the elements. Usually the top and bottom elements each have their own thermostat and are wired so that only one element comes on at a time. Normally the upper thermostat comes on first, and then when the water in the top of the water heater is hot, the upper thermostat re-directs the electricity to the lower thermostat and element.
High limit switch
The high limit switch is a circuit breaker that is activated by heat. When the water in the water heater gets too hot it trips the high limit switch. The switch is in the top thermostat and has a red button. To reset the switch push in the red button.
Drain Valve
The drain valve allows the water heater to be drained for various reasons including periodic removal of sediment or for replacement. In areas with hard water it is recommended to drain at least 5 gallons of water from the drain valve every six months or so to prevent sediment build up.
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