Sewage ejector pump problems
Short answer
Stop using the fixtures served by the basin. Keep the lid closed. If the alarm is on, use a clearly marked external silence button only when safe, and call for service. Short cycling, odor and a pump that runs without moving water can each have several causes.
Sewage ejector pump problems almost always come down to five things: a float switch that hangs or fails, a check valve that leaks or is in backwards, a lid or vent that is letting sewer gas into the room, a pump that will not run because of power or a jam, and an alarm nobody knew the pit had. Unlike a grinder station in the yard, an ejector basin sits inside the house, under a bathroom, garage apartment or pool house, so a problem is smelled or heard before it is seen.
Here is what each symptom means on an indoor basin, what the Zoeller and Liberty manuals say about it, and what a homeowner may safely do.
Safe steps, in order
Nothing here opens the panel or the basin. If a step does not clear it, stop and make the call.
Step 1: Stop sending water to the basin
An ejector pit serves specific fixtures: the ones below the main drain line. Stop using those. Fixtures that drain by gravity to the sewer can keep going.
Step 2: Silence the alarm at its box
Ejector alarms are usually a separate box on the wall. Some alarms, including the Zoeller indoor APak, have backup power for the alarm. Use the marked external silence control only if the area is dry and safe. Follow the alarm’s own instructions for the indicator or reset.
Step 3: Note what lost power
Tell the technician whether the pump, its alarm or another circuit lost power. A GFCI and a breaker respond to different conditions. Do not reset electrical equipment that is wet or repeatedly trips.
Step 4: Leave the lid sealed and call
The IRC, which Alabama adopts for residential plumbing, requires a gas-tight cover on a sewage ejector sump. Opening it releases sewer gas into the living space. Request service.
Problems by symptom
The Liberty P380/P680 troubleshooting table describes symptoms to report. Which checks apply depends on the pump, float and alarm installed in your basin.
- Starts and stops too often (short cycling)Zoeller lists a tight float, a check valve stuck or missing, or a pit that is too small. Liberty: a pump that runs periodically with no water in use means the check valve. Pumped sewage drains back and the pump re-pumps it.
- Runs without moving waterLiberty names a jammed impeller or a closed valve; Zoeller lists discharge head beyond capacity, air, or voltage.
- Will not shut offZoeller lists debris under the float or a float that is bound. Liberty: the float hung on the basin wall.
- Will not runThe technician checks the power supply and switch, then tests the pump and level control for the installed model.
- Alarm going offThe float at the top of the basin is submerged. Same causes as any of the above, plus a pump that simply cannot keep up with a full house.
- SmellThe gasketed lid, the vent connection or the discharge union has lost its seal, or sewage is sitting in a basin that rarely cycles.
The float switch
Some ejectors use a tethered float, others a vertical float or a separate controller. A blocked float can prevent the pump from starting or stopping. The technician checks the switch and its clearance against the model instructions.
Leave the cover and electrical connections in place. A technician can test the float and pump separately.
Alarm, backup and power
An ejector alarm is a float on its own circuit. Zoeller's residential systems pair an indoor APak alarm with battery backup; Liberty's duplex controller alarms on battery when power is out but cannot run the pumps on it. So a sewage pump battery backup, as people search for it, keeps the alarm alive, not the pump. Without power the pump does not run, exactly as with a grinder station. Keep water away from the basin's fixtures until power returns or a generator is connected by someone qualified.
Code points that explain the symptoms
The 2021 International Residential Code, which Alabama's plumbing board rule 720-X-1-.02 makes the statewide residential standard, requires an ejector sump to have a gas-tight cover, a check valve and a full-open valve on the discharge, and a pump that passes 2-inch solids where it takes a toilet. Zoeller's instructions add a 2-inch vent to the sewer vent system, Schedule 40 discharge pipe rather than DWV, the check valve arrow pointing away from the basin, and an inspection every three months. A basin missing any of those is where smell, short cycling and backflow start.
What we check
Float operation, position and cord routing; the check valve and its orientation; the discharge shut-off valve; the lid gasket, vent and discharge union for gas leaks; running current and the capacitor; the impeller for a jam; the GFCI and receptacle; the alarm float and its battery; and whether the basin and pump are sized for the fixtures they serve. Repair and installation of ejector systems each have their own service page.
When it is urgent
Sewage at the basin lid or at the lowest fixture it serves, a strong sewer gas smell in a bedroom or living space, or sparks or burning at the receptacle: stop all water to those fixtures, ventilate the room, and call. Short cycling and a faint smell are prompt visits.
Still not right? Ask from here
Your name, a way to reach you and what the pump is doing. That is all we need to start. Town and utility are optional.
Sewage backing up or overflowing? Stop using water and call now: (251) 850-8031. On a utility-owned pump, call your utility first.
Questions people ask
Why is my ejector pump running constantly or keeps running?
A float that is stuck up, debris under it, a jammed impeller or closed valve so it cannot pump down, or a leaking check valve so it never gets ahead. Zoeller and Liberty list all of these. Stop using the fixtures on that basin and request service.
Why does my ejector pump smell like sewage?
The basin is sealed and vented by code, so a smell means a lid gasket, vent connection or discharge union has opened, or sewage has sat for a long time in a basin that seldom cycles. Do not lift the lid to check; have the seals inspected.
What does an ejector pump alarm mean?
A labeled high-water alarm means the basin level is above the alarm sensor. A separate low-battery or trouble signal can mean something else. Stop using the fixtures that feed the basin and report the alarm label and model to the service provider.
Do I need a battery backup for a sewage ejector pump?
The battery on an alarm such as the Zoeller APak powers the alarm alone. A pump needs its own backup supply. If you do not know what equipment has backup power, keep the fixtures that drain into the basin out of use during an outage.
Is a sewage ejector pump the same as a grinder pump?
No. An ejector moves sewage with solids intact from a basin to a gravity drain; a grinder shreds it and pushes it under pressure to a sewer main. The grinder vs ejector guide covers the difference and which your home has.
Sources and facts
- Liberty P380/P680 manual: troubleshooting table: pump will not run; runs without moving water (jammed impeller or closed valve); runs periodically without water in use means check valve. Liberty Pumps P380/P680 sewage system manual 1167000A, www.libertypumps.com/… (read 2026-11-04)
- Liberty PDC-Series duplex controller: on battery backup the panel can alarm but cannot run pumps. Liberty Pumps PDC-Series duplex controller manual, www.pumpproducts.com/… (read 2026-11-04)
- Zoeller 912 manual: APak indoor alarm 86 dB with battery backup; outdoor alarm NEMA 4X 82 dB; basins 18x30 in = 30 gal, 24x24 in = 41 gal. Zoeller 912 residential sewage ejector systems manual, manuals.plus/… (read 2026-11-04)
- Zoeller sewage pump instructions SW1316: 2-inch Schedule 40 discharge (not DWV), check valve arrow away from basin, 2-inch vent to the sewer vent system, GFCI receptacle, inspect every 3 months. Zoeller sewage pump instructions SW1316, zoellerathome.com/… (read 2026-11-04)
- 2021 IRC P3007: sewage ejector sump with gas-tight cover; check valve plus full-open valve on the discharge; 2-inch solids for ejectors receiving toilets. Alabama rule 720-X-1-.02 makes the 2021 IRC the residential plumbing standard. 2021 IRC P3007 (sumps and ejectors) via up.codes/…; adopted for Alabama residential plumbing by rule 720-X-1-.02, admincode.legislature.state.al.us/… (read 2026-11-04)