Sump pumps are installed particularly where basement flooding is seen as a problem, but are also used to ameliorate dampness where the water table is normally above the foundation of a home. Sump pumps send water away from a house to any place where it no longer presents a problem, such as a municipal storm drain or a dry well.
Older properties may have their sump pumps connected to the sanitary sewer, but this is frowned upon now (and may be against the plumbing code or at least municipal bylaws) because it can overwhelm the municipal sewage treatment system.
Sump pumps are usually hardwired into a home’s electrical system, and may have a battery backup. Some even use the home’s pressurized water supply to power the pump, eliminating the need for electricity. Since a sump pit may overflow if not constantly pumped, a backup system is important for cases when the main power is out for prolonged periods of time.