A sewage ejector pump lifts wastewater and sewage from a fixture below the sewer line, such as a basement bathroom, up to the gravity sewer main. It sits in a sealed pit and passes solid waste, unlike a sump pump, which only moves clean groundwater.
Some fixtures sit lower than the main sewer line. A basement bathroom or a laundry room below grade cannot drain by gravity. A sewage ejector pump solves that. It collects the waste in a sealed pit, then lifts it up to the gravity sewer main so it can flow out of the house. On a larger scale, a municipal sewage lift station does the same job for a whole neighborhood.
How a sewage ejector pump works
The pump sits inside a sealed basin, called a pit or sump. Waste from the below-grade fixtures drains down into it. A float switch turns the pump on when the level rises. The pump's impeller then pushes the sewage up a discharge pipe to the main sewer line above. Plumbing code sets the basin size. The International Plumbing Code calls for a pit at least 18 inches in diameter and 24 inches deep, with a gastight cover. A check valve on the discharge line keeps the lifted waste from draining back into the pit.
It is not a sump pump
People mix up the two because both sit in a pit. They handle very different water. A sump pump moves clean groundwater away from a foundation. A sewage ejector pump moves raw sewage, including solids from a toilet. That harder job needs more muscle. Code requires an ejector serving a toilet to pass spherical solids up to 2 inches across. A plain sump pump cannot do that and would clog. The two also follow different discharge rules.
Ejector vs grinder pump
A grinder pump is the next step up. Instead of passing whole solids, it grinds waste into a fine slurry. Zoeller notes a grinder pump builds high pressure to push that slurry long distances or into a pressurized city main. A sewage ejector instead moves larger volumes short distances at a modest lift. A typical unit like the Zoeller Model 267 is 1/2 HP with a 2-inch discharge and passes 2-inch solids. Choose a grinder only when the run is long or steep.