Grinder pump running but not pumping
Short answer
If the run light is on, the pump hums and the level does not fall, stop using water and request service. E-One tells owners not to touch the valves, so leave every valve alone. Causes: air lock, a closed valve, a backwards check valve, a torn stator, or too much head.
A grinder pump running but not pumping has its motor turning while the basin level stays put. The manufacturers list the same short set of reasons: air trapped in the pump (air lock), a discharge valve closed at the station or the street, a check valve stuck or installed backwards, a stator or cutter that can no longer move sewage, or a discharge head higher than the pump can reach.
It is the one grinder fault where the pump sounds fine and is not. Here is how to recognize it and what clears each cause.
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: Confirm the symptom
Run light on (amber on Keen, yellow on Myers, Pump Running on E-One Sentry), a steady hum from the basin, and drains that do not improve while it runs. If the horn or alarm light is on too, follow the alarm steps as well.
Step 2: Stop using water
The pump is not lowering the level, so every gallon in stays in. Hold laundry and dishes and keep flushing to a minimum.
Step 3: Leave the valves alone
E-One's safety tips tell owners not to touch the valves. A closed or half-closed valve is on the list of causes, but which valve, which way, and whether the check valve is backwards is for the technician; a wrong turn here sends sewage the wrong way.
Step 4: Request service, and mention any recent work
Air lock is most common right after a pump change or a basin pump-out. Myers lists air lock on a new install first. If anyone has worked on the station lately, say so when you call.
Possible causes
From the Keen, Myers, Liberty, Barnes and Goulds tables for a pump that runs without delivering.
- Air lock. Keen: start and stop the pump several times and check the volute vent hole. Myers: air lock on a new installation. Goulds: pumps that run but do not pump are probably air locked. Keen adds that an Off float set too low lets the pump draw air and lock itself.
- A closed valve. Keen: discharge valve closed. Myers: ball or gate valve off, or the valve at the street turned off.
- A check valve stuck or installed backwards. Keen and Liberty list it; Myers specifically names the redundant check valve at the right-of-way installed backwards.
- A clogged inlet or discharge. Keen: inlet or discharge valves clogged. Myers: a clogged grinder inlet, or the tap at the force main obstructed.
- A damaged stator on a progressive cavity pump (Keen and E-One are that type; BCSS installs Keen). Barnes lists stator damaged or torn under insufficient capacity. A torn stator spins without sealing against the rotor, so nothing moves.
- Head beyond the pump’s capability. On the Myers WG20 curve, 105 feet is the zero-flow limit. A technician checks the actual discharge head against the exact pump curve at the required flow. A maximum-head number alone cannot show whether the pump can move enough wastewater.
- A worn or jammed cutter (Barnes) that lets the motor turn but blocks flow.
Grinder pump air lock
Air lock happens when the pump's volute fills with air instead of liquid, usually after the basin was pumped dry, a new pump was set, or an Off level lets the pump run until it draws air. A centrifugal impeller spinning in air generates no pressure; a progressive cavity pump can also lose prime. The manufacturers' remedy is to cycle the pump so the air escapes and to make sure the small vent hole in the volute or discharge is clear. Both are done from the panel and at the pump, so both are technician steps. Goulds goes further and drills relief holes where air lock keeps recurring.
Local angle: the pressure in the street
On a low-pressure sewer the pump pushes into a shared main. Gulf Shores Utilities specifies a residential pump able to deliver 10 gallons per minute at 90 feet of total dynamic head; North Baldwin and Loxley specify 7 gallons per minute at 185 feet. A pump chosen without that number can run but not deliver on a long or busy main, especially at peak times. Where the main's pressure has risen since the pump was installed, the same pump can go from fine to not pumping with nothing broken.
What we check
Whether the level drops while the pump runs; running current (a pump on air draws low, a pump against a closed valve draws differently again); every valve between pump and main, including the street valve and the redundant check valve's orientation; the volute vent hole; stator and rotor condition on progressive cavity pumps; cutter and inlet; and the delivery against the head the utility specifies.
When it is urgent
Running without pumping is urgent from the start, because the storage is counting down and the motor is working for nothing. Sewage at a fixture or the lid makes it an emergency: stop all water.
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 grinder pump running but not pumping?
Most often air lock, especially after recent work on the station. Otherwise a valve closed at the station or the street, a check valve stuck or installed backwards, a torn stator or jammed cutter, or a discharge head the pump cannot reach.
How do you fix an air-locked grinder pump?
By cycling the pump so the air escapes and clearing the vent hole in the volute, as Keen and Myers describe. Both are done at the panel and the pump by a technician. If it recurs, the Off level or the vent arrangement is adjusted.
Can I open a valve to get it pumping?
No. E-One tells owners not to touch the valves. Opening the wrong valve on a pressure sewer can let the main push back toward the house. Leave them and call.
Does running without pumping damage the pump?
It can. A progressive cavity stator running dry wears quickly, and a motor running at length without moving liquid heats. The manufacturers' run-dry protections (E-One's Sentry Protect Plus shuts the pump down on a run-dry) exist for this reason.
Sources and facts
- Keen O&M p.9: runs, doesn't pump: air lock (start/stop several times; check volute vent hole); OFF float set too low; inlet or discharge valves clogged; discharge valve closed; check valve stuck closed or backwards. Keen Pump O&M-KPCG (May 2022), keenpump.com/… (read 2026-11-04)
- Myers manual p.8: runs but no pumping: air lock on new install; check valve flapper stuck; ball/gate valve off; valve at street off or redundant check valve backwards; tap at force main obstructed; clogged grinder inlet; head too high. Maximum pump head at zero flow is 105 feet. Pentair Myers WG(X)20 owner's manual 23833A744, www.pentair.com/… (read 2026-11-04)
- Goulds IM038 p.5: if pumps run but don't pump they are probably air locked (drill relief holes). Goulds Water Technology IM038R08 grinder pump manual, www.xylem.com/… (read 2026-11-04)
- Liberty PRG manual p.10: check valve stuck or backwards; valve closed; total head beyond pump capability. PRG spec p.7: shut-off head 50 feet. Liberty Pumps ProVore PRG-Series installation manual 2399000, www.libertypumps.com/…; Liberty Pumps PRG-Series engineering specifications, www.libertypumps.com/… (read 2026-11-04)
- Barnes OGV manual p.12: insufficient capacity: voltage, restriction, check valve stuck/backwards, shut-off valve closed, cutter jammed, airlock, stator damaged/torn. Barnes OGVF/OGVH installation manual (Form 108890 Rev X), d1pkofokfruj4.cloudfront.net/… (read 2026-11-04)
- E-One D-Series spec section 1.05: 7.8 gpm at 185 ft (80 psig). Owners guide p.4: do not touch the valves. Sentry brochure p.2-3: temporary pump shutdown for run-dry. E/One D-Series specification, eone.com/images/files/d-series-spec.pdf; E/One Owners Guide (LM000403 Rev G), eone.com/…; E/One Sentry Alarm Panels brochure (LM000323 Rev H), eone.com/… (read 2026-11-04)
- BCSS installs Keen progressive cavity pumps. BCSS System Care: Grinder Pumps, www.baldwincountysewer.com/… (read 2026-11-04)
- GSU grinder specs: residential minimum two horsepower, ten gallons per minute at a total dynamic head of ninety feet. Gulf Shores Utilities grinder specifications, www.gulfshoresutilities.com/grinder-specs (read 2026-11-04)
- North Baldwin Utilities and City of Loxley specifications: minimum 7 gpm against 185 feet of discharge head. Loxley Water and Sewer Specifications (March 2019, Sec. 2.5), www.cityofloxley.com/… (read 2026-11-04)