Sewage Ejector Pump and Ejector Basin, Explained

Why a basement bathroom needs a pump

Drains work by gravity: waste flows downhill from each fixture into the main sewer line, which leaves the house at a fixed depth.

When a toilet or shower sits lower than that line, as it often does in a finished basement, the waste has nowhere to go, and a sewage ejector pump solves that by collecting it and pushing it up to the gravity drain.

The system has three parts. A sealed basin, buried in the floor, receives waste from the low fixtures. A submersible pump in the basin, switched by a float, turns on as the level rises. And a discharge pipe carries the waste up and over to the gravity drain or sewer.

It is not a sump pump. A sump pump moves groundwater from a perforated pit and must not take sewage. An ejector handles toilet waste and must be sealed and vented as part of the drain system.

How a sewage ejector pump moves waste uphill

1. Fill: Waste from the basement toilet, shower or sink drains into the basin through its inlet; one maker’s basins use a 4-inch inlet ¹.
2. Float rises: When the level reaches the set point, the float switch turns the pump on. One maker presets its floats and says not to adjust them ¹.
3. Pump runs: The pump pushes waste up the discharge pipe. Sewage pumps should not be smaller than 2 inches, one maker says ¹.
4. Check valve closes: When the pump stops, a check valve keeps the column of waste in the pipe from falling back into the basin ¹.
5. Vent breathes: Air moves through the vent as the level drops and rises, keeping the basin at atmospheric pressure ³.
6. Alarm stands by: If the level keeps rising because the pump failed, a high-water alarm sounds ¹.

Ejector, grinder and other sewage pumps compared

Example: how pump size sets the lift

One maker’s published specs for its Pro-Series ejector systems show how far each pump can push before flow stops (shut-off head) ¹; the chart plots them. The table lists the other limits a pump has to meet, which matter as much as height.

Shut-off head is the height where flow drops to zero. A pump needs to work well below that height to move the 20 gallons per minute California’s code requires for toilet waste ². That is why a pro sizes the pump from the vertical lift and the length of the discharge run.

The ejector basin: the sealed pit the pump sits in

The ejector basin is the tank buried in the basement floor that holds the pump and collects the waste.

Look for a round lid flush with the floor, bolted down with a gasket, with two pipes rising out of it: the discharge and the vent.

One maker’s basins hold 41 gallons in a 21 × 30-inch or 24 × 24-inch size, with the top lip level with the finished floor ¹.

California’s plumbing code requires sumps and receiving tanks to have substantial covers with a bolt-and-gasket manhole or equivalent opening, and a vent large enough to keep the sump at atmospheric pressure, at least 1½ inches, run through the roof or combined with other vents where allowed ³.

Liberty’s manual says cords passing through the cover must be sealed in their channels to keep sewer gas from leaking out ¹.

Basins are set in pea gravel or washed crushed stone, not sand or native soil, so they stay level and supported ¹. Some cities require a basin that withstands a 10-foot stack test; one maker sells basins built for that ¹.

On an invoice, the basin may be listed separately from the pump. The diagram above stacks the parts in the order you would meet them standing over the lid, with the code minimum that applies to each.

What an ejector system makes possible

What an ejector pump cannot handle

An ejector stops in a power outage. Plan on not using the basement fixtures until power returns, or ask a plumber about backup options. Liberty also says not to pump water over 140°F with its pumps ¹, so hot discharges such as some appliances need checking against the manual.

Solids-handling ejectors are made for human waste and toilet paper. Wipes, rags, paper towels and grease jam impellers and floats. LA County Public Works urges keeping fats, oils and grease out of drains to prevent backups ⁵, and that applies doubly to a pump.

What makes an ejector system cost more or less

We do not print prices, because fair numbers need dated local quotes. For a new system: breaking and patching the concrete floor, basin size, simplex or duplex, pump horsepower for the lift, the discharge and vent runs, a dedicated circuit, the alarm, and permits.

For a replacement pump: access, whether the check valve and gate valve are replaced too, whether the basin and cover seals are sound, and cleanup if the basin overflowed. Our cost guide explains plumbing price drivers.

We found no independent lifespan figure for ejector pumps we could verify; it depends on use, what goes down the drains and the pump model. Check the maker’s warranty.

How an ejector system is installed

A summary of one maker’s installation manual ¹ and California code points ²³. This is licensed-plumber work in most places, with a permit and inspection.

1. Plan the location, discharge route and vent route; pull the permit.
2. Break the floor and excavate the pit; bed the basin in pea gravel or washed crushed stone, never sand or native soil ¹.
3. Set the basin level, with its top lip at the finished floor, and connect the inlet ¹.
4. Connect a discharge of at least 2 inches in a single dwelling, with a union, then a check valve, then a gate or ball valve ¹².
5. Run the vent at least 1½ inches through the roof or to an allowed vent connection ³.
6. Seal the cover gaskets and cord channels so no sewer gas escapes ¹.
7. Plug the pump into a dedicated, grounded circuit at least 4 feet above the floor; no extension cords ¹.
8. Install the high-water alarm, test several cycles, and pass inspection.

How to keep an ejector pump running

• Flush only toilet paper and waste; no wipes, even "flushable" ones.
• Keep grease out of basement sinks ⁵.
• Test the alarm regularly using its test button, if equipped.
• Listen for the pump running too often or too long.
• Have a plumber clean the check valve and inspect the pump on a schedule; the gate valve exists to make that possible ¹.

Warning signs and when to call

• The high-water alarm sounds.
• Sewer odor near the basin lid.
• The pump hums but does not pump, or runs without stopping.
• Basement fixtures drain slowly or back up.
• A clunk and backflow after each cycle: a failed check valve ¹.

When the alarm sounds, stop using all basement fixtures and call for emergency plumbing. See also sump pumps and basement water.

What the plumbing code requires of a sewage ejector

Ejector size (2025 California Plumbing Code §710.3, UPC-based): ejectors receiving toilet or urinal waste need at least 20 gpm capacity.

In single dwelling units they must pass a 1½-inch solid ball and have a discharge pipe of at least 2 inches with a backwater valve and gate valve. Other occupancies need a 2-inch ball and 3-inch discharge ².

Covers and vents (§710.10): covers with a bolt-and-gasket manhole or equivalent; a vent large enough to keep atmospheric pressure, at least 1½ inches, through the roof or combined where permitted; vents from air-operated ejectors may not combine with other vents ³.

Alarm: Liberty’s manual states the UPC requires sewage systems to have an audio and visual alarm ¹. California’s code has an alarm section (§710.9); confirm the local text.

Electrical: one maker requires a separate, fused, grounded branch circuit per the National Electrical Code ¹. IPC states use different section numbers. Rules checked 2026-10-12.

Ejector pump vs. similar pumps

Ejector pump myths that lead to clogs and odors

Myth A sump pump can handle a basement toilet.

Reality Toilet waste needs an ejector in a sealed, vented basin ³.

Myth The basin lid just keeps things tidy.

Reality Code requires a bolt-and-gasket cover; cords must be sealed to keep gas in ³¹.

Myth A check valve is optional.

Reality One maker recommends it to stop backflow every cycle; California code calls for a backwater valve on the discharge ¹².

Myth Flushable wipes are fine.

Reality Wipes are a leading cause of jammed sewage pumps.

Myth The alarm is extra.

Reality Liberty cites the UPC as requiring an audio and visual alarm ¹.

How local code and storm outages affect an ejector

When you need an ejector pump and when to replace one

You need an ejector if a toilet, shower or sink sits below your sewer line and you want it to drain without a separate gravity route. Replace the pump when it hums but will not pump after a clog is cleared, trips the breaker, or the alarm keeps sounding with no blockage.

Next step: find your basin and alarm, test the alarm, and post a "no wipes" note in the basement bathroom.

Related terms

Grinder Pump

A grinder pump is an electric sewage pump, set in an underground tank on a property, that chops household wastewater into a fine slurry and pushes it under pressure through a small pipe to the public sewer when the sewage cannot flow there by gravity.

Sump Pump

A sump pump is an electric pump that sits in a pit, called a sump, in the lowest part of a basement or crawlspace and pumps out groundwater that drains into the pit before it can rise onto the floor.

Plumbing Check Valve

A plumbing check valve is a one-way valve that lets water or wastewater flow in only one direction and closes automatically, using a hinged flap, spring-loaded disc or ball, when flow stops or tries to reverse, so the pipe cannot drain backward.

Residential Drain Line

A residential drain line is any pipe in a house that carries used water and waste away from sinks, tubs, toilets and appliances, flowing by gravity on a steady downward slope to the building drain and then to the sewer or septic system.

Plumbing Venting

Plumbing venting is the network of air pipes connected to a home’s drains that lets air in and out as water flows, so the pressure in the drains stays balanced and the water seal in each fixture trap is not sucked out or pushed through.

Main Sewer Line

A main sewer line, for a house, is the single underground pipe that carries all of the home’s wastewater from the building drain out to the public sewer main in the street or an easement, and in many places the property owner is responsible for it along its whole length.

Drain-Waste-Vent (DWV) System

A drain-waste-vent (DWV) system is the network of sloped pipes, traps and vents in a building that carries used water and sewage by gravity to the sewer or septic system while letting air in and out so drains flow smoothly and sewer gas stays out.

Septic Tank Effluent Filter

A septic tank effluent filter is a removable screen, usually a slotted cylinder set inside the tank’s outlet tee, that catches solids still floating in the treated wastewater before that liquid flows out to the drainfield.

Also referenced from: Main Sewer Line, Floor Drain, Sump Pump, Grinder Pump, Plumbing Check Valve, Septic Tank Effluent Filter, Drainage Fixture Unit (DFU)