How do dishwashers work?

Date Posted:17 February 2020 

We take a close look at how dishwashers work and provide you with some useful tips to help you better identify issues with your machine when they arise so you’ll know what to do when they breakdown.

Just ask anyone what the least preferred activity around the home or commercial kitchen would be, and they are likely to respond; ‘doing the dishes’. A response both understandable and expected. Well, thanks to a little invention called the dishwasher and those fortunate enough to own one this once overbearing task became a lot easier to bear.

It’s incredible just how quickly we adapt and change the way we do things, and you may never have given a thought to how dishwashers work until one day they inevitably let you down. In busy commercial kitchens, a breakdown can have disastrous implications, and nobody knows better than an experienced kitchen hand just how quickly dishes pile up, cluttering the kitchen and hampering workflow.

So today, we’re going to take a close look at how dishwashers work and provide you with some useful tips and insights so you will know what to do when they breakdown.

Who invented the dishwasher?

The first-ever dishwashing machine was invented in 1850; by Joel Houghton, crafted from wood and hand-powered, the device was crude and cumbersome to use and not very useful. In 1865, L.A. Alexander attempted to improve on the concept; however, like its predecessor, it was not very popular.

The first successful dishwasher was invented in 1886 by a woman, Josephine Cochrane, who along with George Butters, a mechanic who helped make her invention a reality. Josephine was a wealthy socialite looking for ways to protect her expensive China from damage during the washing process. When revealed at the 1893 World’s Fair in Chicago, the device was called Lavadora, then later changed to the more aptly named Lavaplatos.

In 1929, over three decades later, the first domestic dishwashers powered by an electric motor were released in Europe afforded only by the wealthy.  By the 1950s, dishwashers had risen in popularity; however, it was not until the 1970s where dishwashers were more common-place in residential homes.

Dishwashers vs hand washing

Most would not argue that dishwashers provide numerous benefits when compared with handwashing; the obvious benefit is the labour-savings from a rather boring and laborious task.

But the true benefits are more far-reaching, such as the eco-friendly water savings due to dishwashers using a predefined amount of water in their wash cycle. Do you know hand washing dishes with the water running uses up to 125 litres more water than a dishwasher? These water savings equate to roughly 5,000 gallons in residential applications alone.

The primary benefits of dishwashers over hand washing are;

  • Reduction of household and commercial water waste
  • Reduce breakages of delicate wares
  • Provide a cleaner and more hygiene wash
  • Free up time spent on washing for other tasks.

Primary dishwasher components.

To better understand how dishwashers work, it’s essential to make yourself familiar with the various components and their function in the washing cycle. Understanding how dishwashers work will help you spot potential issues as they appear and assist those looking at purchasing a new dishwasher make a more informed purchase.

Machine Housing

The exterior of the dishwasher is made from durable steel or plastic with a stainless-steel or powder-coated white finish. Commercial dishwashers, in particular, need to be exceptionally durable to withstand the harsh knocks which often occur in the foodservice industry.

Wash Tank

The wash tank is filled at the commencement of each wash or rinse cycle. The wash tank, when filled acts as an immediate water source during its spray and rinse cycles. Detergent is added to the water during the wash cycle, and rinse-aid is added during the rinse cycle.

Wash Rack

The wash rack provides a structured way in which to stack kitchen crockery and utensils in an organised manner. Correct loading of the machine is essential to ensure water from the spray arms has unobtrusive access to all areas of the crockery during the wash cycle. Most wash racks have a separate area to stack utensils or silverware.

Motor

The motor is what drives the dishwasher rotating arms and water pumps. Electric motors are used in a variety of applications and renowned for their durability and longevity.  Some connecting components do wear over time such as drive belts, bearing housings and seals. Many washers are switching to direct-drive, a system where the motor directly drives the drum. 

Water Pump

Drain and rinse pumps draw water into your machine during the filling cycle and drain water from the water tank between wash and rinse cycles.

Spray Arms & Nozzles

Dishwashers have two spray arms; one located on the top and another underneath the wash rack. The spray arms have numerous spray nozzles strategically positioned on the arms.  During the wash and rinse cycles, the spray arms rotate, pumping water through the nozzles under high-pressure onto the dishes. 

Control panel

The control panel is located above the door and usually has a screen, or buttons and knobs and interacts with the control board which manages the wash cycles.  The control panel also displays errors when they occur and also provides the status of the current wash cycle.

Switches

Dishwashers have numerous switches that perform a variety of functions. Some switches monitor the open and closed status of the door, preventing the wash cycle from commencing if the door is open. Flood switches monitor water levels to ensure the tank is either filled or empty depending on the stage of the wash cycle. Flood switches can cause significant havoc when faulty causing the machine to overfill and flood the kitchen. 

Timers

The timer is located on the control panel and records the amount of time spent during each of the wash cycle processes.  A faulty timer can play havoc on your entire wash cycle and the quality of the wash results. 

Thermostats

Thermostats regulate water temperature between the various stages of the cleaning cycle and ensure that water is hot enough to aid in the sanitisation process while cutting off when the water reaches the required temperature. 

Heating Elements

The heating element is located at the dishwasher base and is responsible for maintaining ambient water and air temperature during the drying cycle, to expedite the process.

Dishwashers cleaning cycle.

Commercial dishwashers are very different from residential dishwashers as the washing demands are far greater; for this reason, the wash cycles are significantly shorter and complete in a matter of minutes.

Although the wash cycles are shorter, the operation is somewhat similar to the residential washer, though how each commercial washer type tackles each task varies.

The residential dishwasher typically has three stages to the wash cycle;

  • Pre-rinse
  • Wash
  • Rinse

What happens inside the machine when the cycles commence unfolds like this;

  • Water enters the washing holding tank and keeps filling until a sensor triggers and supply cut

  • The water is heated to a high of 160C

  • For dishwashers with pre-rinse detergent dispensers - detergent is added to the water

  • The water-pumped through the spray-arms and jets through nozzles under pressure directly onto the dishes.

  • Displaced water is filtered and returned to the holding tank, reheated and pumped back through the spray arms, and repeated until the pre-rinse cycle is complete, which tends to be only a few minutes long.

  • When the wash cycle begins, detergent is added to the water and sprayed on the dishes. The process repeats for the duration of the wash cycle, which can take up to 1hr to complete.

  • At the end of the cycle, water is pumped from the tank and refilled

  • On some machines, rinse aid is added to the water.

  • The water is once-again reheated up to 160C redirected through the spray arms.

  • When the rinse cycle is complete, a heating element drys the dishes and the cycle terminates.


The commercial dishwasher process is very different from your typical home dishwasher.  Busy kitchens require a significant amount of bench space for stacking dirty dishes, pre-soaking cutlery, loading wash racks and pre-rinsing plates before the dishwasher is loaded.

As an example of how commercial dishwashers work, I'm going to step-through the wash cycle of the rack dishwasher.  Although there are only two stages to the wash cycle, there are various steps required to ensure you get optimum performance. 

In a commercial kitchen, the kitchen-hand is responsible for washing dishes and thus responsible for the operation of the dishwasher.  The wash process in a commercial kitchen would look something like this;

  • Stack dirty dishes close to the pre-rinse sink and sprayer
  • Pre-soak cutlery in a small tub
  • Place dirty dishes into a wash rack - take care not to overload as wash performance diminishes
  • Pre-rinse racked dishes over the pre-rinse sink using the sprayer
  • Place the wash rack in the Rack Conveyor and close the hood

Next commences the two-stage wash process;

  1. Wash cycle: superheated water with added detergent agent sprays dishes under pressure to remove any food residence or scum from crockery, cutlery or pots and pans.
  2. Rinse/dry cycle: superheated water with added rinse agent sprays dishes under pressure and thoroughly rinses any detergent or food residue from crockery. Some rack-conveyors have heating elements installed to thoroughly dry the dishes at the end of the rinse cycle. This entire process takes between 90-120 seconds, depending on the commercial washer type.

When the crockery, utensils and pot ware exit the machine, the rack moves along the bench with each additional rack which exits the washer until a rack triggers a sensor at the end of the bench. The triggered sensor prevents any further washing until bench space is made available.

Dishes are removed from the racks and placed on a commercial kitchen trolley ready to be returned to storage.  This process is repeated continuously throughout the day.

Water use in modern dishwashers.

Many old-generation washers used around 10 gallons of water per load. New standards legislated in 2013 required dishwashers to be more water-efficient. These new standards resulted in significant water savings with consumption dropping to levels between 3 to 5 gallons depending on how energy-efficient the model.

How you load your dishwasher determines results.

Dishwashers will do most of the work without intervention as long as the wash rack is correctly loaded.

For best results, here are some simple tips we recommend you follow;

  1. Never overload the dishwasher:  Overloading diminishes wash results. Be sure to leave enough room for water to reach the dishes for best results.
  2. Stack your dishes carefully:  Always face the dirtiest part of your crockery towards the spray arms and never stack similar objects on top of one another this enables water from the jets to do the best possible job.
  3. Be careful of what you place in your dishwasher:  Delicate objects such as crystal or china dishes can be easily damaged in the wash cycle - wash all delicate items by hand instead

Is it necessary to pre-rinse dishes?

Yes, we recommend removing large particles before you rack your dishes as large food particles might be left behind after completion of the rinse cycle. 

Are pre-rinse aids necessary?

Rinse aids help reduce water spots on dishes and allow them to dry much faster. Many dishwasher detergents already include a small amount of rinse aid; however, use a separate liquid rinse aid delivers better results.

The rinse aid is dispensed at the end of the last wash cycle and assists water to more efficiently run off your dishes. Rinse aids speed up the drying process and eliminate water stains and residue left on kitchenware. 

Are eco-friendly detergents effective at cleaning?

In the past, eco-friendly dishwasher detergent was not as effective as those traditionally available. That's not the case anymore. Eco-friendly detergents are not only better for the environment and your health but achieve the same results as traditional detergents.

Eco-friendly dishwasher detergents are usually phosphate-free and tend to be more expensive than their regular counterparts. All in all, green detergents are just as effective as traditional ones, but you will need to choose the product that's right for your washer.

Simple care tips to help increase machine longevity.

Want to get the most out of your dishwasher? You will have to take care of it, and it's easier than you might think. Just follow these simple tips, and you enjoy many years of trouble-free dishwashing:

  1. Use only dishwasher detergent: Dishwasher detergents have a unique formula which activates with the heat and water movement inside the dishwasher. Traditional dish soap may be effective for hand washing dishes, but it can leak out of your dishwasher and cause damage.
  2. Don't overcrowd your dishwasher: Although it can be tempting to overload your dishwasher in the hope, it will all magically become clean, in reality, they will simply emerge dirty. 
  3. Clean the dishwasher once a month: To prevent debris from building up inside your wash it's recommended you clean your dishwasher monthly. Simply fill a cup with vinegar, put it on the top rack and run a regular wash cycle. Then, after the first cycle, sprinkle some baking soda on the inside floor and run a short rinse cycle. Open the door and allow air to flow and dry the dishwasher. 

Our Final thoughts

We hope the above information has provided you with a few insights into your dishwashers components and their function in the washing cycle, and it might help in the event your dishwasher breaks down.

By caring for your washer correctly, avoid overloading, regular cleaning and use of right detergents and rinse aids your commercial dishwasher will serve you for many years to come.


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