How to Clean and Descale your Dishwasher

Author: Tracey Freinberger   Date Posted:18 November 2019 

The root cause of many dishwasher problems result from the lack of care, such as failing to follow manufacturer guidelines cleaning and maintaining your machine. We take a close look at the common dishwasher issues and provide some useful insights on how

Over the last six decades, dishwashers have proven their worthiness in commercial kitchens, due to their capacity to wash vast quantities of crockery, pots, glasses and utensils fast, efficiently and effectively.

Fortunately, the majority of today’s dishwashers handle all of these quintessential demands with flying colours. It’s for this very reason why dishwashers have become the cornerstone of the commercial kitchen - but what happens when your dishwasher’s performance starts to wane?

The root cause of many dishwasher problems is the direct result of the lack of care, such as failing to clean the machine at regular intervals suggested in the manufacturer’s guidelines. In this article, we aim to reveal how to clean your dishwasher and provide some useful tips on preventative care, so you get the most out of your machine. 

Tell-Tale signs cleaning your washer is well overdue.

Aside from visible scum on your machines inner walls and cleaning rotors, here are a few other signs a little maintenance is well overdue.

  • Food particles appearing on washed crockery
  • A reduction in your washers overall cleaning performance
  • Overpowering smells emanate from your machine.

If any of the above sound familiar to you, it’s time you considered your dishwasher needs an immediate clean and some well-deserved maintenance.

To help you understand the importance and value of some preventative care, we have created a rather intensive guide on how to clean and descale your dishwasher with some compelling reasons as to why you should.

Damaging effects of neglecting dishwasher care.

I certainly can’t think of any manufactured items which do not require some routine maintenance or care schedule and your dishwasher is no exception.

Although commercial dishwashers are designed to withstand the rigours of daily non-stop operation and some pretty rough handling, failure to follow the basic care instructions can result in your machine wash quality declining and even component failure.

To understand why this may occur, it’s a good idea to have an understanding of how commercial dishwasher’s work and how to troubleshoot dishwasher problems.

How do dishwashers work?

Although there are significant differences in the quality, features, capacity and performance of every dishwasher, the majority of dishwashers follow a similar process shown below;

  1. Your dishwasher is connected to a hot-water source.
  2. At the start of the washing cycle, water flows into the dishwashers tank.
  3. Water within the holding tank is heated to a minimum of 80°C (176 degrees Fahrenheit).
  4. During the wash-cycle soap is added simultaneously through a dispenser as water is pumped from the tank and sprayed under pressure through fine-jets located on your washers rotor arms.
  5. Dirty water is drained from the machine.
  6. The rinse cycle commences and heats water from the dishwashers tank and delivers the water under pressure as done during the wash-cycle.
  7. The machine drains once more.
  8. Depending on your washer, dishes are air-dried to the selected setting.

The above is a simple walk-through and by no-means details the finer operations which occur during the wash cycle which control and monitor the entire wash process.

The above process reveals two primary areas where machine components are exposed to potential contaminants, those areas are;

  • Water source
  • Food particles and bacteria from dirty dishes.

Hard water and your machine.

Connecting your dishwasher directly a commercial or residential water source exposes your dishwasher to harmful contaminants which over time, can corrode your dishwashers water tank and clog your machines spray jets and destroy other machine components.

What makes tap water harmful to machinery? Hard water contains a high mineral content of calcium and magnesium carbonates, bicarbonates and sulphates. In commercial applications, hard water poses a problem, regularly identified as the cause of equipment failure, in particular, water-tanks, cooling towers and boilers. Hard water use forms deposits over time called “scale”, the buildup of these deposits can clog pipes and jets, cause corrosion and rust in tanks and also lead to overheating and component failure due to impaired water flow.

Dishwashers are subject to the buildup of limescale deposits. These deposits, not only present a hygiene risk but can result in heating element failure; for this reason, we recommend regular removal of limescale deposits. Descaling should be performed by a qualified service technician, in accordance with the manufacturers descaling instructions.

Scale if left untreated can cause;

  • Premature failure of heating elements
  • Effect the accuracy of electrical sensors and produce false readings, causing the machine to be non-compliant to the standard
  • Effect wash and rinse performance through blocked water jets
  • Result in the build-up of food scraps on top of scale resulting in bacteria growth.

Fortunately, there are preventive measures you can take to ensure the longevity of your commercial dishwasher and prevent costly repair and service fees.

How to descale your commercial dishwasher.

  1. Drain the dishwasher and refill with fresh water
  2. Add 500ml of a good quality descaler to the wash tank and run for 10 minutes
  3. Inspect and run for a further 10 minutes if needed
  4. If there is any heavy build-up use descaler neat with a scourer to remove heavy deposits

Note: It is vital to ensure skin and eye contact do not occur, wear gloves and safety goggles.

Installing a commercial water filter prevents untreated hard water from entering and damaging the components of your machine. Industrial water filters are designed to soften water by removing minerals responsible for water hardening such as ions, calcium and magnesium, which can directly impact on the longevity of your appliance.

How often should you descale a dishwasher?

We highly recommend descaling your dishwasher at least once a year with our tested and approved quick descaler for dishwashers to protect against the build-up of limescale deposits and to prolong the life and performance of your appliance.

Tips on cleaning your dishwasher to avoid descaling.

Follow the steps below to protect your dishwasher from harmful limescale;

  1. Drain the machine every night, rinse and check that the following are clear of blockages & debris.
  2. Clean scrap trays and filters at the end of each shift.
  3. Wash and rinse jets: wash all parts under a jet of running water, clean nozzles thoroughly, using a toothpick or pointed tool if necessary.
  4. Occasional use of a commercial liquid descaler will assist with the removal of detergent & calcium build up in the wash chamber of your machine. Using Zexa Chemicals does not require the use of a descaler.  Do not use abrasive products to clean the tub.

Note: The Food Standards do not recommend the use of vinegar and lemon juice unless they have been verified and validated to be effective. See for more information on chemical sanitisers or check out our article on cleaning and sanitising commercial kitchens at

Achieving the best results from your dishwasher.

One of the best ways to achieve optimum results from your dishwasher is to ensure those operating it understand how to use and clean your dishwasher after each shift.

Some ways you can achieve the best wash results are;

  • Scraping off excess food from plates, dishes and pots before loading.
  • Use the correct wash agent suggested by your manufacturer.
  • Clean your dishwasher after each shift.
  • Use a commercial liquid descaler or water softener.

Note: Check with your dishwasher manufacturer before using liquid descalers or water softeners, as they may be unsuitable for some machines.

Final thoughts

Without a doubt a little preventative care of your dishwasher will go a long way to ensure the longevity of your machine - dishwashers can and do deliver decades of service when cared for and maintained as per manufacturer guidelines.

In summary, the most relevant information we would like you to garner from this article are;

  • Consider installing a commercial water filter to prevent hard water from entering your machine.
  • Consider using a liquid descaler every few months to prevent the buildup of scale in your machine.
  • Seek an experienced technician if your machine is already heavily scaled.
  • Follow manufacturer guidelines and clean your machine daily.

By following these simple steps will not only increase the reliability and longevity of your machine but also aids in preventing harmful bacteria buildup within your machine.

We hope you have found this article useful and encourage you to comment below if you have anything further you would like to contribute to the discussion.

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