Grinder pump noises: humming, rattling, grinding
Short answer
A short hum per cycle is normal. Grinding or rattling means the cutter is rubbing or chewing on something hard; a hum with no pumping suggests a jammed impeller or failed start capacitor; a chattering panel means failing floats. Stop using water, note the sound, and request service. Do not lift the lid to listen.
A grinder pump makes some noise: a brief motor hum from the basin each time it cycles, and on some panels a click as the contactor pulls in. The sounds that matter are the ones that changed. A louder grinding than before, a rattle, a hum that goes on without the level dropping, or a panel that chatters all have a named cause in the manufacturer tables.
Here is how to sort normal from not, and what each abnormal sound usually means.
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: Listen from above the lid
Stand near the station during a cycle. Note whether the sound is a smooth hum that ends when the pump stops, a metallic grind or rattle, a hum that drags on, or a repeated clicking from the panel. Do not lift the lid; the sound carries fine through it.
Step 2: Watch the panel
If the run light stays on while the noise continues and no water seems to leave, the pump is running without pumping. If the horn or light comes on, follow the alarm steps.
Step 3: Cut water use and book service
A pump that is chewing on something or rubbing its cutter ring is wearing itself out with each cycle. Reduce the cycles by reducing water, then get it looked at. There is no safe homeowner step inside the basin.
What each sound usually means
Matched to the manufacturers' noise and capacity tables.
- Metallic grinding or scrapingThe grinder impeller is rubbing the grinder ring. Keen lists misalignment, a bent shaft or an object stuck in the grinder. Hydromatic lists no clearance between impeller and cutter. Barnes lists a broken cutter.
- Rattling or clankingA hard object in the cutter (a bottle cap, a toy, aquarium gravel from E-One's do-not-flush list), or rigid piping attachments transmitting vibration (Barnes).
- A hum that goes on without the level fallingA partly clogged grinder (Keen, Myers), air lock, or a start capacitor that has failed so the motor hums without turning (Keen, Zoeller). Barnes describes the locked-impeller test as a current reading near locked-rotor amps.
- A rumble or growl that gets louder over monthsBad bearings (Hydromatic), or a cutter running at too high a pressure (Barnes).
- Clicking or chattering from the panelKeen says chattering contactors come from failing floats or floats in turbulence. The contactor is pulling in and dropping out as the float bounces.
- A loud buzz or hum from the panel itselfA relay or contactor under strain. Treat any buzz with heat or smell as an electrical emergency.
Possible causes
For the noise complaints we get, in order.
- Something in the cutter that should not have been flushed: wipes wound into rope, floss, a hard object.
- A partially clogged grinder, which also brings overload trips (Myers).
- Worn bearings or a cutter and ring that have lost clearance from years of grinding.
- Floats bouncing in turbulence, chattering the contactor.
- A failed start capacitor: hum, no rotation.
- A bent shaft after a hard jam (Keen).
What we check
The cutter and ring for objects, wear and clearance; shaft runout; running current and start current; bearing noise with the pump pulled; float movement and contactor condition in the panel; and the discharge pressure, since Barnes ties a noisy pump to operating at too high a pressure. On Keen pumps the impeller and retainer plate are the only field-replaceable grinder parts; deeper work goes to an authorized center.
When it is urgent
A hum with no pumping is urgent, because the storage is counting down while the motor heats. Any buzzing, crackling or smell from the panel is an electrical emergency: switch the grinder breaker off at the house panel and call. A grind that still pumps is a booked visit.
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
Does a grinder pump make noise?
Yes, a little. Expect a short motor hum from the basin each cycle and a click from the panel as it starts. Neighbors should not hear it. Grinding, rattling or a hum that will not stop are the sounds to report.
Why is my grinder pump humming?
A hum during a normal cycle is the motor. A hum that continues with the level not dropping means the pump is running without pumping: a jammed or partly clogged cutter, air lock, or a start capacitor that has failed so the motor cannot turn. Reduce water use and request service.
My grinder pump is making a loud grinding noise. Is it broken?
It is grinding something it should not, or grinding on itself. Keen lists the impeller rubbing the ring from misalignment, a bent shaft or a stuck object; Barnes lists a broken cutter. The pump may still work today, and it is wearing fast. Book service.
The panel keeps clicking. What is that?
The contactor pulling in and dropping out. Keen attributes chattering contactors to failing floats or floats in turbulence. It is a float repair before it becomes a contactor repair.
Sources and facts
- Keen O&M p.9: grinder impeller rubbing the grinder ring from misalignment, bent shaft or a stuck object; grinder partially clogged; start capacitors blown. Control panel O&M p.4-5: chattering contactors from failing floats or floats in turbulence. Keen Pump O&M-KPCG (May 2022), keenpump.com/…; Keen Pump General O&M, Control Panel, keenpump.com/… (read 2026-11-04)
- Myers manual p.9: partially clogged grinder causes noise and overload; yellow run light stays on with a partially clogged grinder or air lock. Pentair Myers WG(X)20 owner's manual 23833A744, www.pentair.com/… (read 2026-11-04)
- Hydromatic manual p.6: noisy: bearings, no clearance at impeller/cutter; overloads motor: clogged, bad bearings/impeller. Pentair Hydromatic HPG owner's manual HYD4530, www.pentair.com/… (read 2026-11-04)
- Barnes OGV manual p.12: noise causes include operating at too high a pressure, broken cutter, rigid piping attachments; locked impeller check by current near locked rotor amps. Barnes OGVF/OGVH installation manual (Form 108890 Rev X), d1pkofokfruj4.cloudfront.net/… (read 2026-11-04)
- Zoeller FM2903 p.2: won't start causes include bound impeller/seal and capacitor. Zoeller FM2903 Installation and Service Instructions, 803/805/807, zoellerpumps.com/… (read 2026-11-04)
- E-One owners guide p.3: do-not-flush list includes kitty litter or aquarium gravel, glass, metal, plastic. E/One Owners Guide (LM000403 Rev G), eone.com/… (read 2026-11-04)
- Keen O&M p.8, p.10: only field disassembly permitted is replacing the impeller and retainer plate. Keen Pump O&M-KPCG (May 2022), keenpump.com/… (read 2026-11-04)