Hobart Commercial Dishwasher Not Draining? Do This Immediately

A commercial dishwasher (warewasher) is the unsung hero of the restaurant industry. It operates in the background, ensuring an endless supply of clean, sanitized plates and glasses to keep the dining room turning.

However, if you open the doors of your Hobart, CMA, or Jackson dishwasher and find the wash tank filled to the brim with dirty, stagnant, greasy water, your dish pit has just ground to a halt. A commercial dishwasher that will not drain is a severe health code violation. Here is exactly how to troubleshoot a clogged warewasher before calling for commercial kitchen repair.

Immediate Triage: Safety First

Before you reach your hands into a commercial dishwasher, you must take precautions:

1. Turn Off the Power: Commercial dishwashers run on high voltage (often 208V to 480V) and contain extremely hot water (160°F+). Turn the main power switch OFF.
2. Wear PPE: The water is caustic due to industrial detergents and sanitizers. Wear thick rubber dishwashing gloves before reaching into the tank.

1. The Clogged Scrap Screen (The Most Common Cause)

Commercial dishwashers are designed to handle residual food particles, but they are not garbage disposals. Waitstaff and dishwashers frequently fail to thoroughly scrape plates before racking them. Inside the bottom of the wash tank, there is a large, perforated metal scrap screen. Below that is a smaller, finer pump intake screen. If these screens become entirely caked with lettuce, napkins, straws, and hardened cheese, water physically cannot reach the drain.

• The Fix: This requires zero tools. Put on gloves, reach into the murky water, and pull out the scrap screens. Take them to the 3-compartment sink and scrub them clean. Once removed, the water in the tank should immediately rush down the drain. Train your staff to empty these screens every 2 to 3 hours during a busy shift.

2. A Jammed Drain Pump or Valve

If the screens are completely clean, but the water still won’t drain, you have a mechanical blockage deeper in the system. Many modern dishwashers use a motorized drain pump to force the water out of the machine and into the floor sink. If a solid piece of debris (like a broken ramekin, a piece of silverware, or a toothpick) bypasses the screens, it will lodge directly into the drain pump impeller, physically jamming the motor. Alternatively, gravity-drain machines use a motorized drain valve. If the actuator burns out or a bone gets stuck in the valve seal, it will not open.

• The Fix: This requires a certified technician. The machine must be partially disassembled to access the pump housing, clear the debris, and verify that the pump motor hasn’t burned out from the jam.

3. Floor Sink Backup (Plumbing Issue)

Sometimes the dishwasher is working perfectly, but the water has nowhere to go. Look under the dish machine at the floor sink/floor drain. If the floor sink is overflowing with water and grease, the restaurant’s main plumbing line is clogged.

• The Fix: You need a commercial plumber or a drain-snaking service to clear the main grease line, not an appliance repair technician.

Preventative Maintenance is Key

A broken dishwasher forces you to switch to paper plates or manually wash dishes in a 3-compartment sink—both of which slow down service and crush your margins.

Preventative maintenance is critical. Contact HP Mechanical for comprehensive commercial kitchen equipment service in the Portland Metro area. We ensure your heating elements are descaled, your pumps are clear, and your dish pit never stops running.