Most sewage systems work using the power of gravity to move solids and liquids down a line. There may be situations where it is simply not possible to put plumbing devices uphill from a septic or city sewage system, however, and in those cases, a sewage pump becomes an indispensable item to move effluent. This type of pump has one job and one job only: to move solids and liquids between locations. A typical one will sit in a sewage basin, which must naturally be in the lowest area of the location needing drained. The pump is capable of being submerged and will likely have to deal with some fluids at nearly all times.
A submersible sewage pump is located at the bottom of basin or receptacle, such as a septic tank. The intake for that pump is located as close to the floor of the basin as possible, often being found on the bottom or near the bottom of the device. The goal is to empty as much of the solids and liquids as possible out of the basin. Because some room must be left between the floor and the pump, however, it is unlikely that total draining will ever take place without manual intervention.
While this pump will mainly handle liquids, there will be times when solids will also need disposed of though a system. Most pumps are capable of handling solids up to 2 inches (5 cm) in diameter. Commercial pumps may be capable of handling even larger items.
The vast majority of sewage pumps work the same way. A bulb is attached to the pump much the same way it may look on a sump pump or even in a toilet reservoir. When that bulb reaches a certain height, it kicks on a switch, starting the pumping action. When the liquids lower the bulb to a certain point, the pump switches off.
The main point for many residential consumers is determining what size of a pump to buy. They are usually rated in horsepower, and most are between 0.5 hp and 1 hp. The size of the pump should be based on the amount of sewage generally needing to be transported, usually expressed in gallons per hour. Generally, household sewage pumps are capable of moving between 5,500 gallons (20,000 liters) and 8,000 gallons (about 30,000 liters) per hour. The cost typically depends on the horsepower rating.