7 components coveredField manual · Sump / Well Pump
Sewage ejector and grinder pump basins: field service manual
Covers: Residential below-grade sewage basins with a submersible solids-handling ejector or a grinder pump, sealed gas-tight lid, vent, discharge with check valve and full-port gate/ball valve, and a high-water alarm. Pressure-sewer grinder stations owned by a utility are out of scope.
When a basement bathroom sits below the sewer, waste drains into a sealed basin and a pump lifts it to the gravity line. An ejector passes solids whole (about 2 in) through a 2 in or larger line; a grinder cuts waste into slurry and can push it farther through smaller pipe. Most calls are float problems, check valve failures, wipes clogging the impeller, and odor from lid seals or vents.
Safety first
- Biohazard: raw sewage. Gloves, eye protection, wash and disinfect after work
- Sewer gas contains hydrogen sulfide, which is toxic and can deaden your sense of smell; ventilate and never put your head into an open basin
- Never enter a basin or pit: confined space. Treat deep pits as permit-required confined spaces
- Lock out the pump circuit and close the discharge valve before breaking any connection
- Methane in sewer gas is flammable: no open flames or sparks near an open basin
How it works
Fixtures drain by gravity into a basin, typically at least 18 in diameter. A float switch starts the pump at the on level; the pump discharges up through a check valve and a shutoff valve to the building drain, and stops at the off level. A separate float sets off a high-water alarm.
Codes for basins taking toilet waste typically require the pump to pass 2 in spherical solids and a minimum 2 in discharge in single-family homes; larger occupancies require 3 in piping and valves. The check valve and gate valve must be accessible (some jurisdictions require them outside the pit), with the gate valve downstream of the check valve.
The basin must be gas-tight with a gasketed, bolted lid and its own vent to the atmosphere; many codes call for at least a 2 in vent and do not allow an air admittance valve as the basin vent. The vent equalizes pressure as the basin fills and empties and carries sewer gas outside.
Grinder pumps produce low flow (manufacturers cite roughly 22-30 GPM) at high head and are used for long runs or pressure sewers; ejectors move more volume (around 66-100 GPM) at lower head over short runs.
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OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): Newly installed sump pump sitting in a basement sump pit by Famartin, CC BY-SA 4.0
