Why Is My Commercial Dishwasher Making a Strange Noise?

Commercial dishwashers aren't silent.

Pumps operate, water moves through wash arms, valves open and close, and drainage systems operate throughout the cycle.

The important question isn't:

"Does the dishwasher make noise?"

It's:

"Has the sound changed?"

A dishwasher that suddenly becomes louder or develops a grinding, humming, rattling, knocking, buzzing or vibrating sound should be investigated.

Depending on when the noise occurs, possible causes can involve the:

Wash pump

Drain pump

Pump motor

Impeller

Wash arms

Foreign objects or debris

Bearings or mechanical components

Water inlet system

Drainage system

Electrical components

Loose components or panels

or another part of the machine.

The sound provides a clue.

Proper diagnosis identifies the cause.

Common Commercial Dishwasher Noises

Different sounds can point technicians toward different areas of the machine.

You may hear:

Grinding

Humming

Buzzing

Rattling

Banging

Knocking

Squealing

Whining

Loud vibration

Clicking

Unusually loud water movement

Intermittent mechanical noises

The stage of the cycle when the sound occurs can be just as important as the sound itself.

Commercial Dishwasher Making a Grinding Noise

A new grinding noise shouldn't be considered normal simply because the dishwasher is still completing cycles.

Depending on the machine and when the noise occurs, possible causes can include:

Foreign material within a pump or wash system

Impeller problems

Pump or motor wear

Mechanical components contacting incorrectly

Damaged rotating components

If the noise is loud, persistent or worsening, continuing to operate the machine may risk additional damage.

A dishwasher still running doesn't necessarily mean it's running correctly.

Commercial Dishwasher Making a Humming Noise

Some electrical motors naturally produce operating sound.

But a new or unusually loud hum, particularly when the expected function isn't occurring, can indicate a problem.

For example, a pump motor may receive power but fail to rotate or move water correctly.

Depending on the machine, possible causes can include:

Mechanical restriction

Foreign material

Pump problems

Motor problems

Impeller problems

Electrical faults

If the dishwasher is humming while failing to wash or drain, repeatedly restarting it isn't the solution.

The cause needs to be identified.

Dishwasher Humming but Not Washing

If the machine fills but you hear humming instead of the normal wash action, the wash or circulation system may require investigation.

Possible areas include the:

Wash pump

Pump motor

Impeller

Water level

Electrical controls

Mechanical restrictions

However, the sound alone doesn't prove that the complete pump needs replacing.

Testing should determine whether the pump itself has failed or another condition is preventing normal operation.

Dishwasher Humming but Not Draining

If the unusual sound occurs specifically during the drainage stage, the drainage system may require investigation.

Depending on the dishwasher, possible causes can include:

Drain pump problems

Foreign material

Drain restrictions

Impeller problems

Drain hose or pipe restrictions

Electrical or control faults

Standing water combined with an abnormal noise can provide useful information when diagnosing the fault.

Commercial Dishwasher Making a Rattling Noise

Rattling can originate from something relatively simple or from a mechanical component requiring repair.

Possible causes can include:

Loose components

Foreign objects

Wash arms contacting ware

Loose panels

Pump-related components

Vibration

Items incorrectly positioned inside the machine

First check that utensils or other ware aren't protruding from the rack and contacting moving components.

If the dishwasher is empty and the rattling continues, the machine may require inspection.

Commercial Dishwasher Making a Banging or Knocking Noise

A sudden banging or knocking sound deserves attention, particularly if it wasn't present previously.

The cause depends heavily on when the sound occurs.

A technician may need to investigate:

Water movement

Wash-system components

Pump operation

Loose components

Pipework

Drainage

Water inlet conditions

Mechanical movement

Tell us whether the noise occurs once, repeatedly or only during a particular part of the cycle.

Commercial Dishwasher Making a Buzzing Noise

Buzzing can have several possible sources.

Depending on the machine, it may involve an electrical or electromechanical component such as a:

Pump motor

Solenoid valve

Relay

Contactor

or another operating component.

Some buzzing may be normal for particular components during operation.

The important signs are that the sound is new, unusually loud, continuous or accompanied by another fault.

Commercial Dishwasher Making a Squealing or High-Pitched Noise

A new high-pitched, squealing or whining sound may indicate a problem involving a rotating or moving component.

Possible areas for investigation can include:

Pump motors

Bearings

Pump assemblies

Other rotating components

The exact source should be located before parts are replaced.

A high-pitched sound alone doesn't identify which component has failed.

Commercial Dishwasher Vibrating More Than Normal

A dishwasher may produce some vibration while pumps and motors operate.

But excessive or newly developed vibration can indicate that something has changed.

Possible causes may include:

Loose components

Pump or motor problems

Mechanical imbalance

Mounting problems

Panels vibrating

Contact between components

Installation or levelling issues

If the vibration is strong enough to make the machine move, shake surrounding equipment or produce significant noise, it should be investigated.

Wash Pump Making Noise

The wash pump circulates water through the wash system on machines using pumped circulation.

If the pump develops a problem, you may notice a combination of:

Grinding

Humming

Rattling

Reduced wash pressure

Poor cleaning

Wash arms not operating normally

Intermittent washing

Machine stopping during the wash stage

A noisy pump doesn't automatically require complete replacement.

The technician may need to determine whether the problem involves the motor, impeller, foreign material, bearings, pump housing or another part of the circulation system.

Drain Pump Making Noise

Where fitted, the drain pump operates when water needs to be removed from the dishwasher.

A change in sound during draining may be associated with:

Foreign objects

Restricted drainage

Impeller problems

Pump wear

Motor problems

or another drainage fault.

If the dishwasher is both making an unusual noise and leaving water inside the tank, tell us when booking the service.

Those symptoms together can help narrow down the problem.

Foreign Objects Inside the Dishwasher

Not every unusual dishwasher noise means a major component has failed.

Small objects can sometimes enter areas of the machine where they shouldn't.

Depending on the dishwasher, foreign material may interfere with:

Wash arms

Filters

Pump systems

Drainage components

Impellers

Correct scraping and filter cleaning help reduce the amount of debris entering the wash system.

If you suspect something has entered an inaccessible part of the machine, don't dismantle electrical or mechanical components unless appropriately qualified.

Wash Arms Hitting Dishes or Utensils

Sometimes the noise isn't a machine fault at all.

A utensil, tray or other item may protrude from the rack and interfere with the wash arm.

This can produce a repetitive:

Click

Knock

Tap

or rattling sound.

Stop the cycle where appropriate and check the rack loading.

If repositioning the ware eliminates the sound, a repair may not be necessary.

If the noise continues with correctly loaded racks, further investigation may be required.

Blocked or Damaged Wash Arms

Wash arms need to move and distribute water as intended by the machine's design.

Depending on the dishwasher, damaged, obstructed or incorrectly positioned wash components can contribute to abnormal operation or noise.

Kitchen staff can inspect and clean operator-accessible wash arms and jets according to the normal cleaning instructions for the machine.

If the wash system is clean but the noise remains, the source may be elsewhere.

Motor or Bearing Problems

Motors and rotating equipment can develop mechanical wear over time.

Depending on the component and fault, deterioration may result in:

Grinding

Squealing

Whining

Rumbling

Excessive vibration

Increasing operating noise

A sound that gradually becomes louder over several weeks can be useful diagnostic information.

Tell the technician whether the noise appeared suddenly or progressively worsened.

Loose Components and Panels

Not every rattling sound comes from deep inside the dishwasher.

A loose panel, mounting point or component can vibrate when a pump or motor operates.

This may explain why the dishwasher only rattles during certain parts of the cycle.

The source should still be identified rather than simply assuming that "commercial dishwashers are noisy."

Water Inlet Noises

If the unusual sound happens specifically while the dishwasher is filling, the water inlet system may need to be considered.

Depending on the machine and installation, the technician may investigate relevant:

Water supply conditions

Inlet valve operation

Water pressure

Pipework

Associated inlet components

A filling noise points toward a different part of the dishwasher than a grinding sound occurring during the wash cycle.

Noise During Draining

If the dishwasher operates normally through washing and rinsing but becomes unusually noisy only while draining, tell us.

This helps focus diagnosis on the drainage stage.

Possible causes can include:

Drain pump problems

Foreign material

Drain restrictions

Impeller problems

Drain pipework

or another drainage-system issue.

Noise During Washing

If the noise begins only once the wash cycle starts, the wash and circulation system becomes more relevant.

Depending on the machine, possible areas include:

Wash pump

Circulation pump

Pump motor

Impeller

Wash arms

Foreign material

Water level

Rotating components

This is why knowing when the noise happens can be more useful than simply saying the dishwasher is noisy.

Noise When the Dishwasher First Starts

A noise occurring immediately when the machine is switched on may have a different cause from one occurring during washing.

Record:

What the dishwasher was doing

How long the noise lasted

Whether the machine continued operating

Whether an error appeared

Whether the noise happens every time

That information can help the technician reproduce and diagnose an intermittent problem.

Clicking Doesn't Always Mean Something Is Wrong

Commercial dishwashers can contain relays, contactors, valves and other components that naturally produce clicks as the machine progresses through its cycle.

A click isn't automatically a fault.

What matters is whether the sound is:

New

Repeated abnormally

Much louder than previously

or accompanied by symptoms such as:

Failure to heat

Failure to wash

Failure to fill

Failure to drain

Machine stopping

or error codes.

What Does the Noise Tell Us?

Grinding During Washing

The wash pump, impeller, foreign material or another rotating component may need investigation.

Humming but No Wash Action

A pump, motor, restriction, electrical issue or related wash-system fault may be present.

Humming but Dishwasher Won't Drain

The drain pump or drainage system may require investigation.

Repetitive Knocking Inside the Tank

Check whether ware is contacting the wash arms.

Rattling Underneath the Machine

Pump, motor, mounting, panels or other mechanical components may need inspection.

Noise Only During Filling

The inlet system or water supply may be relevant.

Noise Only During Draining

The drainage system becomes a more likely area for investigation.

Squealing or Grinding That Is Getting Worse

Mechanical wear or a rotating component may require prompt attention.

Should I Keep Using a Noisy Commercial Dishwasher?

That depends on the sound and the symptoms accompanying it.

A minor noise caused by an incorrectly positioned utensil can be corrected easily.

A loud grinding noise, stalled motor, severe vibration, burning smell, electrical symptoms or sudden major change in operation is different.

If the dishwasher appears unsafe, switch it off using the normal isolation procedure and arrange professional assessment.

Continuing to operate equipment with an obvious mechanical or electrical fault can potentially cause additional damage.

Don't Wait Until the Dishwasher Stops Completely

This is where preventative action can make a difference.

A commercial dishwasher may continue operating while a mechanical component begins deteriorating.

Your staff hear the change.

But because the dishes are still getting washed, the machine stays in service.

Then the problem gets worse during a busy shift.

A new noise can be an opportunity to investigate the problem before it becomes complete equipment downtime.

What Can Kitchen Staff Check Before Calling a Technician?

1. Check the Rack

Make sure utensils, trays and other items aren't interfering with moving wash components.

2. Clean the Filters

Clean operator-accessible filters and strainers according to the dishwasher's normal cleaning procedure.

3. Inspect the Wash Arms

Check operator-accessible wash arms for obvious debris or obstruction.

4. Listen to When the Noise Happens

Is it during:

Filling?

Heating?

Washing?

Rinsing?

Draining?

This is extremely useful information.

5. Describe the Sound

Tell us whether it sounds like:

Grinding

Humming

Buzzing

Rattling

Banging

Squealing

or vibration.

6. Record the Noise

If practical, take a short video or audio recording.

An intermittent sound may not occur when the technician arrives.

7. Record Other Symptoms

Tell us whether the noise happens alongside:

Poor washing

Standing water

Leaks

Slow filling

Failure to start

Machine stopping

or error codes.

8. Provide the Brand and Model

Different commercial dishwashers use different pumps, motors and operating systems.