1. Normally, a residential water heater with two elements will have only one element operate at a time. If the upper element fails, the water heater will supply no hot water. If the lower element fails, the water heater will still have 1/3 of the tank with hot water.
  2. With a two-element water heater, the lower element and thermostat will cycle more frequently than the upper element and thermostat. For this reason, the lower element will normally accumulate lime faster and fail more often than the upper element. Lower elements will fail more often than upper elements.