What is a lift station?
Lift station: Sewage pumping station in a collection system
In short
A lift station is a pumping station in a sewer system that lifts wastewater from a low point to a higher elevation, so it can keep flowing by gravity towards the treatment plant. It consists of a wet well that collects the sewage, two or more pumps, level controls and a pressurised discharge pipe called a force main.
Lift stations are the most common single project type in wastewater capital plans: Klarifi has extracted 585 lift station projects and 1,213 pump station projects from published US city capital improvement plans.
How a lift station works
Sewers are laid to fall continuously, so in flat or rolling terrain they end up too deep to dig economically. A lift station is placed at that low point. Wastewater collects in the wet well; when it reaches a set level, floats or a level transmitter start a pump, which pushes the sewage through a force main to a manhole at a higher elevation, where gravity takes over again. The pumps alternate to even out wear, and a second pump starts when inflow exceeds what one can handle.
Most modern stations are submersible, with the pumps sitting in the wet well on guide rails. Older and larger stations have a dry well beside the wet well so that pumps can be serviced in the dry. Small package stations serve a single subdivision; regional stations move tens of MGD.
What fails, and why cities keep rebuilding them
A lift station is a single point of failure. If the pumps stop, the wet well fills and sewage overflows from the lowest manhole or backs up into basements: a sanitary sewer overflow that has to be reported to the regulator. Stations therefore have redundant pumps, high-level alarms sent over SCADA telemetry, and standby power from a fixed generator or a connection for a portable one.
Rags and wipes clog impellers, hydrogen sulfide corrodes concrete, steel and electrical gear, and pumps and controls wear out in 15 to 25 years. Rehabilitation therefore comes round continuously: pumps, wet-well lining, valves, control panels, generators and odor control.
Lift station or pump station?
The terms overlap. Lift station usually means a sewage station that raises flow a short height into a gravity sewer. Pump station is the broader term: it also covers stations that push wastewater over long distances, and stormwater and drinking-water pumping. Capital plans use both, often for the same kind of asset, so Klarifi tracks them as two neighbouring project types.