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How to Fix a Commercial Dishwasher That Won’t Drain

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How to Fix a Commercial Dishwasher That Won’t Drain

In the fast-paced environment of commercial kitchens, a properly functioning dish machine is not a luxury—it’s a necessity. When a commercial dish machine stops draining, operations can grind to a halt. Dirty water pooling in the machine not only disrupts workflow but can also lead to hygiene violations, foul odors, and potential equipment damage.

This article is designed to walk you through diagnosing and fixing a commercial dish machine that isn’t draining, plus offer tips for ongoing maintenance to avoid future issues.

7 Reasons Why Your Commercial Dishwasher Won’t Drain

There are many reasons why a commercial dishwasher could fail to drain properly. Understanding what’s going wrong can help streamline your repair process. Here are the most common culprits to watch out for:

  1. Clogged Drain or Drain Hose
  2. Faulty Drain Pump
  3. Improper Installation
  4. Broken or Cracked Drain Solenoid Valve
  5. Kinked or Damaged Drain Lines
  6. Electrical or Control Board Malfunction
  7. Incorrect Detergent Use

1. Issue: Clogged Drain or Drain Hose

A clogged drain or drain hose in a commercial dishwasher prevents water from properly exiting the machine, causing it to either back up or not drain at all.

This can lead to a variety of issues, including leaks, standing water at the bottom of the dishwasher, and even potential damage to the machine over time.

A clogged drain or drain hose is the most common cause of a blockage. 

Fix: Unclog them before continuing to use your machine. 

Disconnect the hose and flush it with hot water. Use a drain snake or brush to clear out any clogs. Make sure that the filter baskets are clean too.

Make sure everything is reconnected securely before restarting the machine.

2. Issue: Faulty Drain Pump

A faulty drain pump can prevent draining because this pump is responsible for removing water from the machine after the wash cycle. 

If the pump malfunctions, it won’t be able to effectively transfer the water out of the dishwasher between cycles, leading to standing water in the machine.

Fix: Check for debris, clear any blockages, and replace if needed.
Check for blockages around the pump area. If it’s not spinning or humming, it may need to be replaced.

3. Issue: Improper Installation

If your commercial dishwasher is installed improperly, it may not drain properly. 

This could be from a variety of issues, including incorrect drain hose placement, kinking, or blockage of the drain hose, or issues with the drain valve or pump. 

These problems can lead to water buildup and potential flooding, as well as foul odors and bacteria growth.

Fix: Reach out to the installation company and/or machine manufacturer to explore repair/replacement options.

Check your hose routing; it may be as simple as the drain hose being too low, kinked, or in a loop. If you suspect poor installation, contact the installer or manufacturer.

4. Issue: Broken or Cracked Drain Solenoid Valve

A broken or cracked drain solenoid valve can prevent a commercial dishwasher from draining because it’s responsible for opening the drain valve to allow water to exit the machine. 

If the solenoid is faulty or blocked, it won’t open the drain valve, and the water will not drain properly.

Fix: Replace it.

These solenoid valves are usually a whole unit and can’t easily be repaired—so replacement is the way to go. Make sure to shut off power before accessing any electrical components.

5. Issue: Kinked or Damaged Drain Lines

Kinked or damaged drain lines prevent proper drainage by creating blockages or restricting the water flow. 

These issues can lead to water buildup in the dishwasher, potentially causing the machine to malfunction or stop working.

Fix: Unkink the drain lines and check for damage. If they are damaged, replace them.

Inspect the entire length of your drain hose. If you see any bends, straighten them. If the hose is torn or worn out, replace it immediately.

6. Issue: Electrical or Control Board Malfunction

An electrical or control board malfunction could prevent draining by affecting the drain pump motor, the drain valve, or the system’s ability to signal these components to operate. 

A faulty control board might not send the correct signal to start the pump or open the drain valve, or it could send a signal for the pump to run continuously—even after the cycle is complete.

Fix: Call in a repair expert or the manufacturer.

Electrical issues can be tricky, so if you suspect this is the case, call in a technician or the manufacturer—especially if your machine is under warranty.

7. Issue: Incorrect Detergent Use

Finally, incorrect detergent use can cause your machine to not drain properly due to excessive suds, which can interfere with the drain pump or clog the drain lines. 

Using the wrong type of detergent, like regular dish soap or laundry detergent, can lead to suds lock, where the excess suds prevent the water from draining properly.

Fix: Stop the cycle and run a defoamer through the machine.

Stop the cycle, remove all dishes, clean out excessive suds, add some defoamer, and run a rinse cycle to ensure any remaining residue is gone. Make sure you’re always using a manufacturer-recommended detergent going forward.

How to Fix a Commercial Dishwasher That Won’t Drain

Now that you know what issues to look for, let’s walk through how to troubleshoot and resolve them. All of the info in our “7 Reasons Why Your Commercial Dishwasher Won’t Drain” section above occurs in Steps 3 and 4 below:

Materials Needed

  • Commercial dish detergent
  • Bucket
  • Microfiber cloth
  • Warm water

Tools Needed

  • Adjustable wrench
  • Multiple Screwdrivers (depending on size)
  • Drain snake or brush
  • Flashlight

Replacement Parts

  • Replacement hoses (if necessary)
  • Replacement screens (if necessary
  • Pump repair kit (if necessary)

Equipment Needed

  • Wet/dry vacuum

Ensure Safety First

Always begin any cleaning or maintenance procedure by putting on the necessary personal protective equipment. For a commercial dishwasher that won’t drain, safety goggles, gloves, and closed-toe shoes should be worn to protect yourself.

5 Steps to Fix a Commercial Dishwasher That Won’t Drain

Follow these steps if your dish machine won’t drain to keep your kitchen in top shape:

  • Step 1: Turn Off and Unplug the Machine
  • Step 2: Prevent Slip and Fall Accidents
  • Step 3: Identify the Source of the Drainage Issue
  • Step 4: Repair or Replace Internal Components
  • Step 5: Test the Machine

Step 1: Turn Off and Unplug the Machine

Start by cutting power to the machine. This protects you and the equipment while you troubleshoot. For hardwired units, disconnect power at the breaker.

Continued power or operation can lead to the dishwasher overflowing or further damage to the machine.

Turning off and unplugging the dishwasher will prevent further water damage, eliminate potential electrical hazards, and facilitate safe repairs.

Step 2: Prevent Slip and Fall Accidents

If your dish machine has overflowed or is at risk of overflowing, place wet floor signs around the affected area to prevent slips and falls. Wipe up any standing water with towels or a wet mop to minimize the immediate hazard.

Step 3: Identify the Source of the Drainage Issue

This is where all of the info we covered in our “9 Reasons Why Your Commercial Dishwasher Won’t Drain” section comes into play.

Now that the machine has been turned off and slip and fall hazards have been eliminated, we need to find where the drainage issue is occurring so we can resolve it.

Commercial dishwashers are made up of many components that could potentially fault and lead to drainage problems. 

Examine each area closely to determine where the water is failing to drain.

Step 4: Repair or Replace Internal Components

Once you’ve determined where the drainage issue is coming from, it’s time to fix it. Depending on where the issue is, you may be able to easily repair or replace the affected component yourself. 

For more extreme problems or repairs involving internal components, we recommend calling in a repair expert or the manufacturer if your machine is under warranty.

Step 5: Test the Machine

Once repairs are made, run a test cycle to ensure the drainage issue has been resolved. Keep an eye on potential problem areas and confirm everything is functioning properly.

When to Call a Professional

While many drainage problems can be fixed in-house, call a technician if:

  • The control board shows error codes you can’t resolve.
  • You’ve replaced or cleaned major parts and the issue persists.
  • There’s visible electrical damage or signs of a short circuit.
  • The machine is still under warranty—unauthorized repairs may void coverage.

Preventative Maintenance Checklist

Avoid major issues by implementing a daily, weekly, and monthly maintenance routine.

Daily Maintenance

  • Remove and clean all filters and baskets.
  • Check for any standing water at the end of the day.
  • Inspect and rinse the spray arms.
  • Wipe down interior walls to remove food and scale.

Weekly Maintenance

  • Remove and clean the drain hose (if accessible).
  • Check float switch movement.
  • Use a descaling product to remove lime scale (if needed).

Monthly Maintenance

  • Test the drain pump and solenoid for wear or resistance.
  • Flush the entire drain system with hot water and vinegar or a commercial descaler.
  • Tighten all hose connections and inspect for leaks or wear.
  • Review detergent use and chemical injection settings with your provider.

Pro Tip: Log all maintenance in a dedicated binder. This will help with tracking recurring issues and may be required for health inspections.

Final Thoughts

A dish machine that won’t drain is more than a nuisance—it’s a threat to the hygiene and efficiency of your kitchen. Fortunately, most drainage problems stem from basic issues like clogged screens, blocked hoses, or a worn-out pump.

By taking the time to understand how your dish machine works and committing to regular maintenance, you can keep your kitchen running smoothly and your dishware sparkling clean.

If you are located in the United States, Canada, or Puerto Rico, there is an Imperial Dade facility near you with experts that can help you implement a preventative maintenance schedule for your kitchen. Keep your kitchen in top shape by reaching out to an Imperial Dade expert today.

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