Primary sump pumps drain water from sump pits to prevent water damage to buildings and belongings. They are the main operating pump while back-up pumps are only used if the primary pump fails. Submersible sump pumps install at the bottom of sump pits with the motor and pump submerged in the water. Pedestal sump pumps have the motor above the sump pit for use in smaller diameter sump pits. Elevator sump pumps drain water out of an elevator sump pit or bank vault and have an oil detector.