Symptoms
- Grinding, rattling, or knocking sound during operation
- Loud humming with little or no water movement
- Noise louder or different than the pump's normal operating sound
Likely causes
- CommonDebris or sediment caught in the impellerSmall stones, sediment, or grit pulled into the pump can cause grinding or rattling.
- CommonPump not sitting level or vibrating against the pit wallA tilted pump can bang or rattle against the sides of the pit during operation.
- PossibleWorn bearings or motor nearing failureAge-related wear often shows up as noise before the pump actually stops working.
- PossibleWater hammer in the discharge pipeA banging sound right when the pump shuts off can be water hammer in the piping rather than the pump itself.
What to do
- Unplug the pump and check the pit for debris or sediment that may have gotten into the intake.
- Confirm the pump is sitting level and stable, not leaning or vibrating against the pit sides.
- Clean the pump intake screen if it's dirty or clogged with fine sediment.
- Check that the discharge pipe is properly supported and not loose, since a banging pipe can sound like it's coming from the pump.
- Note whether the noise happens during normal running or specifically at shutoff, since that points to different causes.
- Replace an older pump proactively if noise is new and the unit is many years old, since failure often follows.
- Have a plumber diagnose persistent unusual noise if cleaning and leveling don't resolve it.
Tools and parts
- Flashlight
- Level
Sump pumpSearch: “submersible sump pump”
When to call a pro
Call a plumber if the noise persists after cleaning and leveling, since the pump may need replacement.
Safety
Use caution
Unplug the pump before reaching into the pit.