Commercial Dishwasher Troubleshooting
Commercial Dishwasher Troubleshooting

Commercial Dishwasher Troubleshooting

Commercial Dishwasher Troubleshooting Commercial dishwashers have proven their reliability and resilience in the marketplace. Dishwashers can wash large volumes of dishes, pots, glassware and cutlery faster than their human counterparts, more cost-effective and hygienic while producing better results.

Commercial Dishwasher Malfunctions

Over time, all appliances eventually breakdown and require servicing and repair due to wear and tear in your washers components. Regular servicing your dishwasher is the best protection for your investment and will ensure its longevity.

As things do go awry at the most inconvenient times, we have prepared our “Intensive Troubleshooting Guide” with tips on how to troubleshoot and repair the most common commercial dishwasher problems.

This guide is designed to provide our audience with insights to enable them to identify which issues require the services of a professional, licensed technician and those that can be carried out by “do-it-yourself-ers”.

The repair or replacement of machine components should always be carried out by a licensed technician to prevent the risk of death or injury.

We hope you find the information in our guide useful.

The most common causes of leaking dishwashers and how to fix them

Dishwashers can leak for a variety of reasons; the first step is identifying the source of the leak. Water leaks can be a result of damaged or deteriorated hoses, seals or pipe fittings, or corrosive limescale build-up resulting in rust and rinse or boiler tank.

1. Boilers & Rinse Tanks

Boiler and rinse tank leaks often occur as a result of rust, a symptom of limescale build-up, replacement the only remedy to the problem. Water hardness is attributed to limescale hardness and varies greatly depending on your business location. Limescale buildup can block inlets, cause damage to washer components or leave sediments behind in your rinse cycle.

Minerals in your water can form deposits on heating elements, boilers and rinse tanks when water evaporates, these deposits are high in magnesium and calcium and are highly corrosive. These corrosive deposits can lead to deterioration of components and rust. Fortunately, there are preventive measures you can take to ensure the longevity of your commercial dishwasher and prevent costly repair and service fees.

Action: Leaky rinse or boiler tanks require replacement.


  1. Clean dishwasher thoroughly every day; staff can quickly learn and step through regular dishwasher clean and descale routines.
  2. Regular descaling of your dishwasher as per your manufacturer manual helps prevent mineral build-up and the onset of rust.
  3. Consider installing a commercial water filter to increase the longevity of your machine. There are many ranges of commercial water filters designed to soften water by removing minerals responsible for water hardening such as ions, calcium and magnesium which directly impact on the longevity of your appliance.
  4. If it is available for your machine, a water softener unit or liquid may be the solution. In the market, the two most common types of systems available to treat hard water are water softener or water descaling system. The water softener changes the chemical composition of the water, whereas the water descaler charges the water and reduces the effects of suspended minerals. Descalers are easy to install and in the long run, cheaper than water softeners. A water descaler can be installed on the pipe without any plumbing and maintenance issues and running costs are low. Probably the most important plus in favour of descaler is that it does not add salt to the water, which water softeners do.

2. O’Rings

O-rings are seals designed to prevent air or fluid passing through a connecting joint and seated in a predefined grove between two or more parts. Both rubber and silicone-based o-rings deteriorate with age, loss of elasticity or contact with corrosive fluids causes the O-ring to break apart.

O’rings are used in a variety of dishwasher components, such as drain and rinse pumps, tap fittings, float valves and pressure switches; for this reason, we recommend a qualified technician identify and resolve the issue.

Action: Replace damaged or deteriorated O’rings.

3. Door Seals

Dishwasher doors have a rubber gasket around the perimeter of the door designed to seal and prevent water from escaping during the wash cycle. Gaskets can suffer from damage or deteriorate with age and become hardened or brittle.

Action: A visual check will be sufficient to determine the integrity of the seal, replace if necessary.

4. Water Inlet Valve

The water inlet valve is responsible for opening and shutting off water flow to the dishwasher. A malfunctioning valve can result in water pooling at the bottom of your washer when not in use – causing the machine to overflow on the next cycle.


  1. Check inlet valve is securely fitted, check external housing for cracks and replace if damaged.
  2. Check connecting hoses or fittings are secure and watertight.
  3. Check if the inlet valve O’Ring is damaged and replace if necessary.
  4. Check the operation of the valve – if sticking, replace the inlet valve.

5. Faulty Float Assembly or Switch

The float assembly and switch are responsible for cutting water supply to your dishwasher when water reaches the required level. As the float rises it toggles the switch shutting off the water supply. If the switch is not activated, water will continue to rise causing your washer to overflow, on the other hand, if the float operation becomes obstructed water supply may be cut off prematurely.


  1. Float: Ensure nothing is obstructing your float from moving freely.
  2. Float Switch: Float switch may be faulty and require replacement.

6. Rubber Elbows

Rubber hoses can deteriorate with age, suffer damage from heat or mishaps during maintenance or repair.

Action: Damage hoses and elbows should be replaced.

7. Wash Bosses & Spindles

Due to the prevalence of hard water in residential and commercial use, wash and rinse-arm spindles are susceptible to limescale build up. Limescale is highly corrosive and results in the loss of part performance or leaks.

Action: Replacement required.

Warning: Leaking dishwashers represent a flood, slip and electrocution hazard and require immediate action by a qualified technician. Why your dishwasher is not draining and what you need to know to fix it There are numerous reasons why your dishwasher might fail to drain, we take a look at the most common issues customers experience.

1. General Checks

  1. Drainage obstructions – food particles or other foreign objects obstructing or blocking water flow, check drain hoses, drain sump and sink drain.
  2. Check the cycle process, has it stopped mid-cycle.
  3. Check power source – does your dishwasher have power or has the cycle been interrupted due to a power outage?

2. Drain Pump

The drain pump is responsible for draining water from your dishwasher at the end of the wash cycle. Several issues can impact on your drain pumps operation, such as blockages, noisy or collapsed bearings, pump failure as well as external factors.

Other factors which can impact the drain pumps operation are inlet valvetimer and selector switches and electronic control board failure. As you might ascertain identifying the source of the problem can be difficult to isolate and best resolved by a qualified service technician.

3. Impeller

The impeller is a mechanical device which creates a sucking force through its rotation and contact with the air or water, used in dishwasher water and rinse pumps they are made from hard-wearing plastic, nylon or metal.

Some dishwashers have two impellers: one to spray the water during the wash cycle and one to drain the water. If your drain impeller is damaged, it will impact on drain performance. Only the drain impeller can impact on your machines ability to drain. Impellers wear with age or can be damaged due to foreign objects, even worn bush sleeves impact on performance and require replacement.

Action: Check impellers for apparent signs of damage or restricted movement.

4. Rinse Pumps

Water pumps perform an essential task in your dishwasher, drawing water to and from the dishwasher during its various stages of the cleaning cycle. Continual use of the rinse pump during washing process directly attributes to its wear and tear and failure of the pump over time.

Two indicators your dishwasher pump may be near the end of its service life is your washers inability to drain effectively or noises emanating from the pump at the end of a wash cycle. Noisy pumps can indicate worn or collapsed pump bearings, and replacement is the best option.

Action: Replace the rinse pump.

5. Solenoid & Timer Control

The solenoid is responsible for opening the drain valve and the timer control is responsible for triggering the solenoid to open the drain valve; a fault in either the solenoid or the timer control can result in drainage issues. If the valve fails to open water will fail to drain from the machine.

Common reasons why your dishwasher stops filling

The reasons why a dishwasher stops filling can be rather extensive, here are the most common causes listed in their order of difficulty.

1. Water Inlet Valve

  1. Filter: One of the first places to check is the water inlet valve filter as it is easy to access. If the filter screen is dirty and clogged with particles, the operation of the inlet valve will be affected. Clean the filter and if the problem persists check the inlet valve.
  2. Inlet valve: Check to ensure the valve is not sticking, any debris is likely to affect the inlet valves operation. If everything looks in order the next item to consider would be the float.

2. Float

Ensure float moves freely; check for signs of general wear and tear or foreign objects hampering its operation or may trigger the float switch causing water to shut off too early in the cycle.

3. Timer

The timer controls a variety of components in the dishwasher have a detrimental effect on the shut-off or start of elements in the control board and control panel.

4. Electronic Control Board

The control board is the central control until which controls the processes of your dishwasher. Control boards are very susceptible to power surges if your control board has power but is not operating the control board could be faulty.

Action: Replace control board.

Why your dishwasher is not cleaning your dishes properly

The manufacturer’s recommendations for cleaning and maintenance of your dishwasher helps aid in your washers overall reliability and performance. If your dishes are emerging from your dishwasher with stains or food residue, there are several reasons why this might be occurring.

1. Filters

Filters are designed to trap dirt, food and other particles during the cleaning process.  If your filters are not regularly cleaned they become clogged inhibit the cleaning process. Replace filters with visible signs of wear or damage.

2. Wash, Rinse Arms & Jets

The rinse jets are essential to the cleaning process by directing water under high pressure to remove food particles and stubborn baked on grime from dishware, utensils and bakeware.

Regular cleaning of your washer helps prevent rinses jets from becoming clogged.  As with all mechanical components, rinse arms can and do suffer from the effects or wear and tear, and in some cases, limescale build-up can inhibit the performance of your dishwashers cleaning effectiveness.


  1. Clean your dishwasher daily as per the manufacturer’s guidelines to avoid limescale build up.
  2. Replace worn or damaged components.

3. Check Chemical/Dosing Pump

The chemical or dosing pump is responsible for detergent added to the wash cycle in the correct dosage. If the pump fails to deliver the proper dosage, this will directly impact on your machines overall wash results.

4. Rinse System

The rinse process is crucial to the overall cleaning efficiency of your dishwasher. The rinse system incorporates a variety of processes to complete the rinse cycle, they are;

  1. Water fills your washers tank and is heated.
  2. Water sprayed under high-pressure onto plates, cutlery and pots delivered through rinse arms and jets that blast away grime and stubborn baked-on grease.
  3. Dirty water is pumped and replenished from your machine several times during the wash cycle to ensure dishes emerge brilliantly clean.

Note: Ensure that rinse arms are working freely, and rinse jets not obstructed by limescale build-up.

5. Wash pumps

Your dishwashers wash pump drives water to your washers spray arms during the wash cycle and are crucial to your dishwashers cleaning efficiency, if your pump is faulty it will need to be replaced.

Simple checks you should make if your dishwasher won’t start

1. Power

Below are a few quick visual and practical checks you can make if your dishwasher won’t start.

  1. Control panel has no power – check your machine is plugged in and switched on, if needed check your fuse box to ensure that your electrical socket also has power.
  2. Control panel has power – check the washer door is closed securely.

2. Door Switches

Contactor relays fitted on doors signal to the control board the door is either in an open or closed position. If the door is open or the contact switch fails to detect a close due to either a door obstruction or faulty door switch the dishwasher will not start.

3. Selector Switch

If your selector switch on your Control Panel is faulty or stuck between settings, your switch will fail to signal the control board and other circuit relays.

4. Motor Relay

The motor relay controls switch the dishwasher motor on or off; if the relay is faulty your dishwasher will not start.

5. Drive Motor

If the power is getting to the motor relay and the relay is not at fault, it is possible that your drive motor is faulty.

Action: Replace as required.

6. Control Board/Timer

As the control board and timer controls essentially when and for how long power gets sent to each component in your dishwasher. Failure in either one of these components will result in your dishwasher failing to start.

Action: Replace as required.

Dishes are still wet after completing the cycle

There are several possible causes as to why dishes may emerge wet after cycle completion.

1. Loading/Stacking of Washer

Overloading or poorly stacking dishes and pots traps water and results in pooling in and around plates or bowls. The best way to prevent this is to ensure you do not overload your machine and dishes don’t touch; this prevents pooling and provides better circulation for dishes to dry.

2. Rinse Air

Some manufacturers recommend using a rinse aid. Rinse aid helps water more easily slide off dishware, reduces spotting and improves the drying process.

3. Thermostats

Thermostats are designed to maintain and regulate the water temperature within the dishwasher and prevents the heating element from overheating the water. A faulty thermostat can cause the water to overheat or not heat at all.

4. Heating Elements

Heating elements are an essential part of your dishwashers washing cycle, to ensure water temperature remains constant and compliant. Water is heated to approximately 15 degrees hotter than most residential hot water systems to kill bacteria and aid in faster drying of dishwasher contents.

5. Dishwasher Cycle Not Completing

There are numerous components in a dishwasher which control the individual processes for each element during the washing cycle. If your dishwasher cycle fails to finish it is possible that one of the many control switches or the control board has gone faulty.

Control Panel Unresponsive

The control panels enable you to interact with your dishwasher by selecting a particular wash or spin cycle. Control panel buttons can stick or become inoperable due to age or fail to advance to the next stage in the sequence and replacement is the only option.

Dishwashers are susceptible to power surges which can blow the control board and could be the reason why your control panel is unresponsive.

Troubleshooting Common Causes of Dishwasher Noise

Dishwashers can be noisy during different stages of their cycle as water is pumped into and out of the machine, this is quite normal. Noise output from dishwashers from different manufacturers can vary significantly so paying attention to the noise output prior to purchase is important.

Sometimes, however, as your machine ages, components wear or fail. Noise can often to be attributed to either worn or collapsed bearings or worn belts.

A dishwasher has various high-speed moving components; the components most susceptible to wear and contribute to the noise of your washer are; water and rinse pump bearings, drive motor bearings, drive pulleys and rinse-arms.

If the bearings are overly worn or collapse in any one of these items, then the noise emanating from your washer will intensify.

Often bearings can be individually replaced, and at other times the component may need replacing altogether. Pumps and motors are the most expensive component to replace in your dishwasher. Pump failure by no means marks the end of your washer; in most cases, your machine will continue to function reliably for many years after replacement of the component.

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