From an article by Aaron Stickley:
A sewage ejector pump, also called pump up ejector system, is used when a bathroom, laundry room, or any other type of plumbing fixture is installed below the main sewer or septic line grade. Sewage ejector pumps are usually installed in basements. The ejector pump is part of a system that can pump both liquids and solids up into the main sewer or septic line.
Sewage ejector pumps are meant to sit in a sump basin that is cut and dug into the ground below grade. The sump basin collects and holds about 30 gallons of waste on average for an average sized home. The drain lines from the various fixtures in the basement area are graded into the side of the sump basin. When the level of waste water in the sump basin reaches a certain height a float on the sewage ejector pump is tripped. The waste water is then pumped out of the basin and up to ground level and then out to the sewer to septic tank. Once the level in the basin goes down the pump turns off until the next time it needs to pump.
A vent is required for a sewage ejector pump installation. The vent comes out of the sump pump and is connected into an existing vent stack or runs up and through the roof. The common outlet size after the sewage ejector pump is 2′. After the pump outlet line there is always a check valve to make sure that nothing drains back into the sump basin after the waste water is pumped out. The top of the sump basin is sealed so that no waste or smell can come out of the top of the basin when it is installed properly.
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