What Is a Sewer Ejector System in a Basement?


Basement remodels or additions present challenges with bathroom installations. Because basements are located partially or completely below ground, plumbing waste from basement bathrooms must be forced upward. A sewage ejector system pumps wastewater and sewage from the basement against gravity up to an overhead sewer line where it exits a house.

Basement Bathrooms

  • Homes with basements usually have sewage pipes that are installed along the basement ceiling. If homeowners decide to finish their basements, perhaps to add an office or a mother-in-law suite, existing sewage pipes cannot accommodate basement toilets. Conventional toilets rely on gravity systems to remove water when they’re flushed. Because basement pipes are located approximately 10 feet overhead, toilets cannot flush upward and sewage ejector pump systems must be installed. These systems pump wastewater from basement toilets up and out to a septic tank or the city sewer line.

Freestanding Design

  • Instead of cutting through a concrete basement floor to install a toilet, a freestanding or above-ground sewage ejector system may be installed. The toilet sits on a platform atop an enclosed system, which is essentially a mini-septic tank, according to BobVila.com. All bathroom fixtures, including toilets, showers and sinks can be connected to this system. A sewage ejector pump within the system receives water and wastewater and discharges it overhead into the home’s main sewer line.

Underground Design

  • Underground sewage ejector systems are more labor-intensive and more costly than freestanding designs. The concrete slab basement floor must be cut and dirt must be excavated beneath the hole to accommodate a holding tank for gravity-draining fixtures and pipes. Toilets are mounted flush on the floor, and not elevated on a platform as in the freestanding design. Since there is no platform to step up on, trip-and-fall accidents are eliminated and toilets are handicap accessible.


  • Although sewage ejector systems fulfill specific plumbing needs for basements, Atlanta’s Ridgeway Mechanical cautions against the common problems of these systems. They are designed to flush only waste and toilet paper; not paper towels, cotton swabs or other commonly flushed items. Many sewage ejector pumps are constructed with plastic impellers that are not durable because they jam easily and break free from the turn shaft. Cast-iron pumps with metal impellers are better choices, according to Atlanta's Davis Plumbing.

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