Introduction to Automated Warewashing: The Seven Key Components

Foodservice warewashing is the method by which a variety of ware types including dishes, glasses, flatware, pots and pans are cleaned by an automated process that employs hot water, motion and detergent. An operation’s automated warewasher is likely its most expensive back-of-the-house piece of equipment, and surprisingly, often operated by employees who receive the least training. An automated warewasher contains seven key components: 1. Tank containing a detergent solution 2. Hood to contain wash and rinse action 3. Pumping and piping system that sprays the detergent solution over the ware 4. Rinse system that receives and sprays the final rinse over the ware 5. Electrical system to regulate wash and rinse action 6. Heating system to maintain wash solution temperature 7. Method by which the ware is conveyed through the system A Stero Sales Representative is a great resource for understanding what is best suited for your facility based on the types of ware you are washing, as well as the volume of your operation. Click here to locate your local Stero representative.


Proper sanitation requires thorough removal of all food particles and other residue to prevent bacterial growth. Stero warewashers meet the challenge every step of the way. All of our products carry the National Sanitation Foundation (NSF) mark and have been tested and certified by NSF to NSF/ANSI (American National Standards Institute) Standard #3—Commercial Warewashing Equipment. NSF issues strict criteria to ensure that warewashing equipment complies with FDA Hazard Analysis and Critical Control Point (HACCP) regulations. To carry the NSF mark, Stero equipment must undergo a rigorous, third-party certification process which tests the following: performance, design quality, materials, soil removal, sanitation efficacy, accuracy of thermometers, thermostats and pressure gauges. nsf-logo-50x50The NSF mark…a symbol you can trust.



Establish the flow of the room by identifying the path that soiled ware takes into the scullery and the exit points for the clean ware. Select the appropriate piece of equipment that possesses the mechanical productivity to match the anticipated volume of ware.

Position the equipment in the room at the strategic location that conforms to the proper flow from soiled to clean. Create dedicated clean and soiled areas to match the flow and minimize the potential for cross-contamination.

Utilize peripheral equipment to increase productivity and save labor expense. These include:

Pre-rinse sink (preferably with a garbage disposal where local code allows) to provide for initial scraping and rinsing, placed close to the machine to reduce labor.

Quick drain, to prevent food and soil from flowing into the wash tank from the soiled table thus reducing detergent usage.

Clean dish table (three rack minimum if space allows) to facilitate air-drying and reduce labor. While square footage is an important consideration in laying out the warewashing area, it is not the only factor. It is equally important to design the warewashing area to support sanitation, safety and an efficient workflow.



Some food products, such as eggs and other dairy items, contain proteins that can cause foaming problems in dishwashers. The detergent supplier can provide formulas designed to eliminate foaming. Thorough pre-scraping of soiled dishware also helps eliminate this problem.



Venting of the dishwasher removes ambient water vapor from the machine. This aids in the drying process and prevents accumulation of moisture on walls and ceilings. Door-Type machines utilize a draft hood which resides above the unit to capture the vapor. Larger machines often employ vent cowls with duct openings. Duct risers fit into the openings and pull the moisture from each end of the warewasher.



When considering a new warewasher for your clean-up process, it is important to consider the following questions before you make your investment.

  • Will the warewasher need venting? If so, what type of venting – draft hood or pant leg ducts?
  • Where will clean and soiled tables be placed? What length will the available space allow?
  • Will there be a shelf for chemicals?
  • Is primary water heat adequate? Will it be able to meet the required demand? What is the temperature range?
  • Will rack shelves be needed for glasses and cups?
  • Are disposal needs adequately addressed?
  • Is a plate shelf required for the landing area?
  • Have shop drawings been carefully checked for adequate breaker sizes, voltage, feed direction and dimensions, and construction of warewashing areas?

Stero Sales Representatives are knowledgeable in all areas of dishroom layouts and can help you to evaluate your needs for the best fit.

Commercial Warewashing Types

Door-Type Machines: designed for small to medium size operations serving 50 to 100 people per meal. They can wash 810 to 1350 dishes per hour. Door-Type washers are equipped with revolving spray arms above and below the dishes. They have automatically timed wash, dwell and rinse cycles and doors slide upward for loading. For energy savings, chemical sanitizing rinse models are recommended over high temperature rinse models. Glass Washers are Door-Type machines which are ideal for bars and bistros because they double as small warewashers. Rack Conveyor Washers: move racked dishes either by a chain or pawl. Pawl action uses a single rod to pull racks through. These units come in one-tank models for medium sized operations (serving 150 people per meal), and two-tank models for high volume operations (where space often restricts the use of a big belt-conveyor machine). Rack conveyors can handle 4500 to 5624 dishes per hour. The dish rack is conveyed through a spray pattern directed from upper and lower stationary spray arms at a prescribed GPM flow rate. After the rack has passed through the wash spray, it moves on to activate the fresh-water final rinse. Flight-Type (Rackless Conveyor) Washers: large capacity Rackless Conveyors are also called Belt Conveyors and Flight-Type machines. They are manufactured for high volume operations catering to more than 1000 people per meal (washing 6750 to 20,000 dishes per hour). The belt conveyors have adjustable speeds and are ideally suited for cafeteria-type operations with heavy tray traffic. Carousel (Circular Conveyor) Systems: offers the most complete, customized machine for the scullery. Integral scrapping, loading and unloading stations provide the space for high-volume applications while allowing flexibility of labor for non-peak times. Tray Accumulators: specifically designed to convey trays either on a conventional flat belt conveyor or as “Tray Accumulators” which use the same amount of space as a flat belt conveyor system, yet handle five times as many trays by utilizing the vertical space above the belt. Tray Accumulators are customizable to fit the space requirements of any operation. Pot, Pan And Utensil Washers: kitchen workhorses, tailor-made for the messy, bulky ware it is designed to clean. Special features offer increased clearance and powerful wash patterns via revolving wash arms. Stainless steel jets spray turbulence to penetrate baked on food and grease and soften food residue. A combination of high pressure and hot water effectively sanitizes all types of ware, including sheet pans and mixing bowls.

Warewashing Basics

There are numerous variables to consider when selecting the right equipment for your dishwashing area: Machine Ratings A dishwasher’s rating is the number of full dish racks it can wash per hour, or, in the case of Rackless Conveyors, the number of dishes which can be washed per hour. The machine’s rating is essential in determining the type and size dishwasher that will be appropriate for your operation. A dish rack is usually about 20” × 20” and can hold roughly 18 dinner plates or 25 to 36 glasses. Capacity will vary based on the size of the items being washed. Specially configured racks are available to accommodate bowls, flatware, etc. Pumps and Motors A warewasher’s pump and motor may be thought of as the machine’s heart and muscle. The pump is measured by its capacity in gallons per minute (GPM). The motor is rated by its horsepower (HP). Together, the pump and motor work to provide adequate water volume and pressure to ensure proper cleaning and regulatory compliance. Heating Equipment Automatic warewashers contain water heaters that maintain the proper water temperature in the unit’s tank. These heaters use either electricity, steam or gas. As a general rule, heaters maintain a tank temperature of 160°F to ensure sanitation. Hot water sanitizing warewashing machines use a booster heater to raise the incoming, general purpose hot water to at least 180°F for the final sanitizing rinse cycle. Rinsing The NSF requires an established amount of heat content to ensure sanitization. The water pressure for this cycle must be between 15 to 25 PSI. Most final rinse systems are controlled with an electric valve known as the “solenoid.” Water pressure is measured by a pressure gauge and regulated by a pressure reducing valve.

Warewashing Guidelines

Like any other piece of equipment, an automated warewasher will function best when installed, operated and maintained properly. Please see the recommendations below to size the right dishwasher to meet your needs.
Meals per hour  Style of Dishwasher
 Up to 50 Undercounter
 50 to 250 Single tank, door style
 250 to 400 Single tank conveyor/Single tank conveyor with pre-wash option
 400 to 750 Double tank, conveyor with pre-wash option
 750 + Flight-Type conveyor

Maintaining Your Warewasher

Each Stero warewasher comes with detailed instructions for maintenance. This includes Stero’s recommendation for a daily cleaning, which will extend the life of the product, improve sanitation and increase efficiency. Stero’s stainless steel construction requires the use of appropriate cleaning tools and solutions to prevent pitting and rusting. Cleaners containing chlorides and highly abrasive tools, such as wire brushes, should not be used to clean stainless steel components.

Did You Know?


  • A warewasher must be thoroughly cleaned at the end of each working shift or at least daily. This includes the machine interior, emptying and rinsing the scrap basket, removing and rinsing wash and rinse arms, and clearing nozzles of any obstructions.
  • Never bang wash arms or rinse arms against hard surfaces to clean. This can damage parts, compromising performance.
  • After replacing all removed parts, leave the machine door open to allow the machine interior to air out and dry overnight.
  • Deliming is necessary if scale is visible inside or outside of the machine. Follow your chemical provider’s instructions for frequency and dosing.
  • Never use steel wool to clean warewasher surfaces; only use products formulated to be safe on stainless steel.
  • Proper water quality can improve warewashing performance by reducing spotting, lowering chemical supply costs, improving productivity and extending equipment life.


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