Above, Figure 1A depicts a typical submersible sump pump system where the pump motor is in a waterproof enclosure and designed to operate below water level. A float switch is used to control operation and comes in a variety of designs, including the free floating type (Figure 1A) as well as internal float or diaphragm designs. A check valve is typically installed to reduce excessive cycling of the pump from back flow.
Figure 1B shows a pedestal sump pump where the electric motor must be above the water level, since it is not in a waterproof enclosure. The float switch is at the motor and is usually not waterproof. The discharge piping and check valve are the same as that of the submersible sump pump. The pedestal and submersible sump pumps are the most common.
Occasionally, even back-up systems fail especially during long term outages. Batteries lose capacity over time and may not be able to power a pump for sufficient time during the power outage. Battery chargers may also fail, leaving a dead battery. Certainly, proper maintenance of these systems plays a major role in reducing failure rate. Another form of power outage is branch circuit failure brought on by too many other appliances plugged into the same circuit as that supplying electricity to the sump pump. Figure 2 shows a sump pump system that failed as a result of branch circuit overloading, considered an improper installation. When a power fluctuation occurs in such an overloaded circuit, the starting current, which is often much higher than the steady state operating current, from the other appliances as well as the sump pump will trip the breaker and render the sump pump system inoperative. A dedicated circuit for the sump pump is certainly recommended.
Figure 3 below is a view of a sump pump plug that was connected to an extension cord. Rust patterns on the plug suggest that the connection was occasionally under water which caused the circuit breaker to trip and sump pump failure, an improper installation. It is not recommended to attach extension cords to sump pumps. Extension cords offer increased electrical resistance, which can drop voltage and damage pump motors. Also the connection (Figure 3) can fall into the sump, an electrical safety hazard as well as a possible obstruction to normal pump operation.
Internal failure of sump pumps occur as a result of wear out or manufacturing defect. In Figure 5, a winding failure in the single phase motor caused non-operation of a new sump pump, which was attributed to a manufacturing defect. There was premature insulation breakdown on stator windings after a very short usage time, a manufacturing defect in this case.
Figure 6 is a view of failed contacts on the pump float switch. This particular case is a wear out failure that was brought on by improper installation. Drain back of water, as the result of a lack of a check valve in the system, caused excessive cycling of the switch and premature failure of the switch. Early contact failure can also be a result of a manufacturing defect such as improper plating or excessive current draw by the motor. The expected life of a sump pump is approximately 10 years, but varies depending on operating hours and number of start/stop cycles.