Commercial Dishwasher Troubleshooting: How to Fix the 8 Most Common Problems
When your commercial dishwasher stops working mid-service, every minute counts. Plates pile up, glassware runs out, and the team is improvising at the wash sink while customers wait. This commercial dishwasher troubleshooting guide is built for that moment — practical, ordered by likelihood, and focused on safe fixes before you call a technician.
We cover the eight problems behind most service calls in Australian kitchens: poor cleaning, drainage faults, leaks, heating failures, spotting, odours, machines that won't start, and wet dishes. We also cover when to repair, when to replace, and the routines that prevent failures.
The logic below applies to Washtech, Hobart, Electrolux, Winterhalter, and most other brands. Always isolate the machine from power before opening panels, and never bypass safety interlocks.
Quick-Reference Diagnosis Table
| Symptom | Most Likely Cause | First Thing to Check |
|---|---|---|
| Dishes still dirty | Blocked spray arms or filters | Remove and rinse filters and spray arm jets |
| Won't drain | Clogged drain filter or hose | Pull strainer; check hose for kinks |
| Water on the floor | Door gasket or hose connection | Inspect gasket for cracks; tighten hoses |
| Water cold or lukewarm | Heating element or thermostat | Check booster temp on display |
| White spots / film | Hard water or no rinse aid | Top up rinse aid; test water hardness |
| Bad smell | Food debris or stagnant water | Drain machine; clean filters and tank |
| Won't start | Power, door switch, water supply | Check isolator, door latch, taps |
| Dishes wet at end | Low rinse temp or no rinse aid | Confirm rinse temp ≥ 82°C |
Narrow the issue with the table, then jump to the matching section below.
Common Commercial Dishwasher Issues and Fixes
The following sections walk through the most common commercial dishwasher issues — from filter and spray-arm blockages to drain faults, gasket leaks, water temperature drops, hard water buildup and dishwasher-not-filling errors — with quick-fix steps for each.
Problem 1: Dishes Not Coming Out Clean (Spray Arms and Filters)
The most common complaint, almost always fixable in-house. Work through these in order — most kitchens find it at step one or two.
Check the filters. Remove the wash tank strainer and any secondary scrap basket and rinse under hot water. A clogged filter forces the pump to recycle dirty water — exactly what you're seeing on the dishes. Clean filters at least once per shift in a busy kitchen.
Inspect the spray arms. Lift them out (most are quick-release) and hold each jet up to the light. Mineral build-up and food fragments block jets, leaving dirty patches in the same spot every cycle. Soak arms overnight in descaler if jets are calcified.
Verify wash temperature. Wash tank should sit at 60–66°C, rinse at 82–90°C. If the display shows lower, jump to Problem 4.
Audit your detergent dosing. Low detergent equals dirty dishes; over-dosing causes etching and residue. Confirm the chemical line isn't kinked, the drum isn't empty, and the dispenser is calibrated to local water hardness.
Review loading. Plates nested too closely, pots obstructing spray arms, and overloaded racks all block water from reaching surfaces. Train staff to scrape and rack — never block spray arm rotation.
If filters, arms, temperatures, chemicals, and loading all check out, suspect a worn wash pump or failing wash arm bearing — that's a technician job.
Problem 2: Commercial Dishwasher Not Draining (Drain and Hose)
Standing water at the end of a cycle is almost always a blockage, not a pump failure.
Pull and clean the drain filter. The tank-bottom strainer is the usual culprit. Lift, rinse, refit. If the tank now drains, you've solved it.
Check the drain hose. Trace it from the back of the machine to the floor waste. Look for kinks (often from the machine being pushed back during cleaning), tight bends, or bulges suggesting internal blockage. Disconnect at the trap end and flush with water.
Inspect the floor waste / grease trap. A blocked floor drain will back water into the dishwasher. If multiple appliances share the drain, you may see slow drainage across the kitchen.
Drain pump. If filter, hose, and floor waste are all clear, the pump may be jammed (cutlery, broken glass, and bone fragments are the usual offenders) or the motor may have failed. A jammed pump can sometimes be cleared by removing the cover and pulling the obstruction out; a failed pump needs replacing — typically $400–$900 in parts plus labour.
If the machine drains slowly rather than not at all, you're usually dealing with partial filter blockage or build-up in the drain hose. Run a descaling cycle and clean filters.
Problem 3: Commercial Dishwasher Leaking — Door Seal and Gasket
Leaks are urgent — wet floors are a slip hazard, and water near electrics can trip safety circuits or cause permanent damage.
Door gasket. Run a finger around the seal feeling for cracks, tears, or flat spots. Trapped food debris also breaks the seal. Clean weekly with warm soapy water; replace every 12–24 months as a matter of course ($80–$200 for the part).
Hose connections. Pull the side or back panel and inspect all clamps and fittings. Vibration loosens clamps over time — tighten with a screwdriver. Replace any split rubber hose.
Wash or boiler tank. A pinhole in the tank is serious — usually long-term descaling neglect eating through stainless steel. Tank replacement is rarely economical on older machines.
Door alignment. If the door doesn't sit square, the seal can't compress evenly. Check hinges for play. On hood-types, worn lift springs let the hood drop unevenly.
Pump seal. Water pooling under the machine specifically while the pump runs points to a failed pump shaft seal — a technician job.
Place towels and a torch under the machine during a wash cycle to pinpoint exactly where water appears — knowing the location halves diagnosis time.
Problem 4: Water Not Heating — Water Temperature, Element and Thermostat
Cold or lukewarm water is a sanitation failure, not an inconvenience. Without 82°C+ at the rinse, you're not killing pathogens.
Check the booster heater. Most machines have a separate booster that lifts incoming water to rinse temperature. If wash is fine but rinse is cold, the booster element has likely failed.
Confirm the hot water supply. If the machine is fed from a hot line and the line is cold (failed water heater, closed isolation valve), no booster can recover fast enough during high-volume service.
Reset the high-limit thermostat. Many machines have a manual-reset thermostat that trips on overheat and locks the heater out. Check the manual for the reset location.
Heating element. A burnt-out element fails a continuity test on a multimeter — a technician check. Replacement runs $400–$800 plus labour depending on model. On three-phase machines, a dropped phase after recent electrical work will let the unit appear to run but starve the heater.
Problem 5: White Residue or Spots on Dishes (Hard Water Buildup)
Spotting looks unprofessional and frustrates front-of-house, but it's almost always a chemistry problem, not a hardware fault.
Rinse aid. Check first. An empty drum or kinked dosing line means water beads on dishes instead of sheeting off, leaving spots as it dries. Top up and confirm the dosing pump is running.
Water hardness. Australian water hardness varies dramatically — Adelaide and parts of Perth are very hard, Sydney and Melbourne softer. Hard water deposits calcium and magnesium as white film. Long-term fix: a water softener sized for your machine's flow rate.
Detergent type and dose. Wrong detergent for the water profile, or under-dosing, both cause filming. Have your chemical supplier test the water and recalibrate.
Rinse temperature. Water too cool doesn't evaporate cleanly, leaving spots. Confirm rinse hits 82°C minimum.
Descaling overdue. A scaled machine redeposits minerals onto dishes. Run a manufacturer-approved descaler monthly in hard-water areas, quarterly elsewhere.
If chemistry and water are both fine, persistent etched-look spotting that doesn't wipe off usually means glass corrosion from over-aggressive detergent — drop the dose rather than increase it.
Problem 6: Bad Smell from the Dishwasher
A smelly dishwasher is one that isn't getting cleaned itself. Customers detect a faint sour smell on glassware, and health inspectors will note it.
Drain the wash tank fully. Stagnant water overnight breeds bacteria. Drain at the end of every service.
Clean filters and tank interior. Pull all filters, scrub the tank with hot soapy water and a soft brush, and rinse thoroughly. Pay attention to corners and the underside of spray arms.
Inspect the door gasket and hinges. Food debris hides in gasket folds and behind hinges, growing mould and producing a musty smell.
Run a sanitising cycle. Most modern machines have a self-clean or sanitise mode — run it weekly with the recommended cleaner.
Check the drain. A dry P-trap on the floor waste lets sewer gas back into the kitchen, which can read as a "dishwasher smell" but is a plumbing issue. Pour a bucket of water down the floor waste to refill the trap.
A persistent smell after a full clean usually means biofilm inside hoses or pumps — a chemical sanitising flush clears it in most cases.
Problem 7: Dishwasher Won't Start, Won't Fill, or Showing Error Codes
Before assuming the worst, work through the basics.
Power supply. Confirm the wall isolator is on, the circuit breaker hasn't tripped, and the plug (if applicable) is seated. On three-phase machines, a dropped phase causes unpredictable behaviour.
Door latch. The interlock switch tells the board the door is closed. A bent latch, worn switch, or food debris stopping the door closing fully will prevent starting. Listen for the click.
Water supply. Check incoming taps are open and the inlet strainer at the back isn't blocked.
Common error code patterns (check your manual for model-specific codes):
- Washtech: E-codes covering wash temperature, rinse temperature, fill faults, and drain faults. Power-cycle first; if the code returns immediately, log it and call service.
- Hobart: F-codes covering overflow, drain timeout, heating, and chemical level sensors. Heating-related F-codes often clear after the machine cools and resets.
- Electrolux: codes typically point to water inlet, drain, heating, or sensor faults. The decode chart is usually inside the front panel or door.
- Winterhalter: alphanumeric codes plus plain-text fault descriptions on newer machines. Connected Wash app gives detailed diagnostics on supported models.
Note the exact code before clearing it — your technician's first question is "what code did it throw?", and a clear answer halves on-site diagnostic time.
Problem 8: Dishes Coming Out Wet (Sanitize Cycle and Rinse Aid)
Wet dishes slow down service and re-wetting at the towel station is a hygiene risk.
Rinse aid first. Same fix as spotting — without it, water clings instead of sheeting off, and dishes don't air-dry.
Rinse temperature. Below 82°C, residual heat can't flash-evaporate water from dishes. Re-check the booster.
Loading. Cups and bowls inverted into rack pockets hold water — train staff to angle items so water runs off.
Rack hold time. Pulling racks immediately doesn't give residual heat time to work. Wait 30–60 seconds, then rack and air-dry vertically.
Ambient humidity. A poorly ventilated dishwash area saturates with steam and slows drying. A canopy hood or extraction fan rated for the dishwasher's steam output is the long-term fix.
If all of the above check out, the rinse jets may be partially blocked — pull and clean them.
DIY vs Calling a Technician
Knowing where the line is saves money and prevents bigger problems.
Safe to DIY:
- Cleaning filters, spray arms, and gaskets
- Topping up and dosing chemicals
- Clearing visible drain hose blockages
- Running descale and sanitise cycles
- Checking and resetting tripped circuit breakers
- Tightening accessible hose clamps
Call a technician for:
- Any fault inside an electrical panel
- Replacing heating elements, thermostats, or pumps
- Boiler or wash tank leaks
- Persistent error codes after a power cycle
- Anything involving gas (on gas-boosted models)
- Three-phase power faults
Cost benchmarks in Australia: service call $150–$250, pump or element replacement $400–$1,200 all-in, new undercounter $4,000–$8,000, passthrough/hood-type $8,000–$20,000, flight/conveyor $20,000–$60,000+.
Rule of thumb: if a repair quote exceeds 40% of replacement cost on a machine over seven years old, replace it. Once downtime, energy efficiency, and warranty are factored in, newer machines often pay back inside two years.
Commercial Dishwasher Maintenance Tips: Preventive Maintenance Schedule
Most dishwasher faults are preventable. Print this and stick it inside the dishwash area.
Daily (end of service): drain the wash tank, remove and clean filters and strainers, wipe the door gasket and interior, leave the door ajar overnight to dry the tank.
Weekly: remove spray arms and clean jets, check rinse aid and detergent levels, run a sanitising cycle, inspect hoses for kinks or wear, wipe down the exterior including air vents.
Monthly: run a descaling cycle (fortnightly in hard-water areas), test wash and rinse temperatures with a probe thermometer, inspect the door gasket for cracks, check chemical dosing calibration, clean the booster inlet strainer.
Quarterly: have a technician check element, thermostat, and pump performance; recalibrate chemical dispensers; verify temperatures against a calibrated probe.
Ten minutes a day, 30 minutes a week, an hour a month — a fraction of the cost of a single emergency call-out.
For broader kitchen upkeep see our Commercial Kitchen Maintenance Checklist, and for sanitisation requirements see Health Inspection Preparation and Commercial Kitchen Temperature Standards.
Frequently Asked Questions
Why is my commercial dishwasher leaving food on plates?
Most often clogged filters, blocked spray arm jets, or incorrect detergent dosing. Clean filters and arms first, verify wash temperature is 60–66°C, and confirm the chemical line is feeding. If all check out, suspect a worn wash pump.
What temperature should a commercial dishwasher run at?
Wash tank 60–66°C; rinse minimum 82°C (some models target 85–90°C). The 82°C rinse is the sanitation threshold required under Australian food safety standards. Test monthly with a probe thermometer.
How often should a commercial dishwasher be descaled?
Monthly in soft-water regions, fortnightly in hard-water regions like Adelaide. Visible scale on the element or inside the tank means you're overdue. Use only manufacturer-approved descaler — the wrong chemical damages seals.
Is it worth repairing an old commercial dishwasher?
If a repair quote exceeds 40% of replacement cost on a machine over seven years old, replacement is usually the better call. Newer machines cut water and energy use significantly, and most carry 1–2 year parts warranties.
Why does my dishwasher trip the circuit breaker?
Usually a failed heating element shorting to earth, water ingress into the control panel, or an undersized circuit. Stop using the machine and call a technician — repeatedly resetting the breaker can worsen the fault or create a fire risk.
Get the Right Machine for Your Kitchen
If your current dishwasher is past its useful life or you're scaling up, the team at CKS can help you size the right machine for your covers, water profile, and bench layout. Browse our full range of commercial dishwashers and commercial glasswashers, or read our commercial dishwasher buying guide to compare undercounter, pass-through and conveyor models. We stock leading Australian and European brands with nationwide installation and after-sales support.
A dishwasher you can rely on is the difference between a smooth service and a kitchen in chaos.
