Product Knowledge Guide: Warewashers

A warewasher can clean almost any item, but specific items, like plastic trays, are better suited for some units than others.


Heating systems can include direct electric heat, steam injection, steam coils or gas, which larger machines generally use.

High-temp warewashers are generally more expensive to purchase, but can be less expensive to operate, as they tend to be much more efficient. These systems use water warmed to180 degrees F to sanitize cleaned ware, eliminating chemical sanitizing residue (typically chlorine) on the ware. Items also tend to dry faster when exposed to room-temperature air after washing. These units utilize a booster heater to raise water temperatures to 180 degrees F and contain heaters to hold water at the proper temperatures for washing and rinsing.

Low-temp dishwashers are often more economical to purchase, particularly for smaller operations. Larger low-temp machines, such as rack conveyors, may include tank heaters, but the building's hot water system will often play the biggest role in getting the water the machine uses to the proper temperature. These use a chemical sanitizing agent in the final rinse cycle.

Smaller models include single-rack undercounter machines, single- and dual-rack lifting door-type machines connected to dish tables and rack conveyor models, which also attach to dish tables. Flight-type rackless conveyors are for higher-capacity applications and eliminate the need to load most ware into dishracks.

It's no longer an industry rule that the size of the machine limits its options. Undercounter dishmachines, for example, can include built-in electric booster heaters, top-mounted slide-out controls, larger door openings, double-wall construction to limit noise and heat loss, "airglide" door designs, fully automatic wash and rinse cycles, touch-panel control systems with digital displays and diagnostics, extended and shortened wash cycles, self-sealing gasketless doors, upper and lower wash and rinse spray systems, removable rack glides for easy cleaning and flexible hoses designed to make installation and maintenance easier.

Door-type machines are effectively undercounter models raised to tabletop height, incorporating a lifting door or hood to speed loading and unloading. These units usually include a faster wash cycle and larger/more robust components for heavier use. Other typical features include door-activated drains, front-mounted tanks for easier cleaning, built-in booster heaters, straight-through or corner-model configuration, top-mounted controls, interchangeable upper and lower spray arms, 1-hp or 2-hp pump motors and detergent/chemical connection provisions.

Rack conveyors move loaded dishracks continually through the machine for greater throughput. They most often feature automatic tank refill, leak-proof doors, rinse-saver devices, 2-hp or 3-hp wash pumps, a door-activated drain closure, removable spray arms and interchangeable spray arms.

Circular conveyor or "carousel" dishwashers are an oval-shaped conveyor that uses a rack conveyor dishwasher as one of its legs. This automates rack travel completely, allowing a higher throughput with similar staffing to a normal rack conveyor.

Flight-type or rackless warewashing units offer the highest capacity and are usually the most efficient machines for large applications. The systems' large removable panels and inclined, self-cleaning tanks are designed to simplify daily maintenance. Double-wall insulation reduces noise and retains heat. These offer one-, two- and three-tank models.

Common Applications

  • Undercounter machines are used most often in bars, kiosks and low-volume operations. These typically have a capacity of 30 to 45 racks per hour, although some faster machines are available.
  • Door-style machines are available in single- and dual-rack models and typically specified for small- and medium-sized restaurants or smaller schools. These units are similar in style to undercounter types, but are taller and connected to dish tables. Capacities for these units range between 21 and 120 racks per hour.
  • Rack or circular conveyor units are geared toward full-service restaurants and higher volume applications such as universities and healthcare foodservice. Average production rate for continuous motion machines is between 100 and 300 racks an hour.
  • Flight type or rackless warewashers are best-suited for large cafeterias, banquet halls and catering operations, as they can wash more than 21,000 dishes per hour with belt speeds as high as 14 feet per minute.
  • Pot, pan and utensil machines are specialty units that offer between a 6- and 60-pan capacity.

Specifying Considerations

  • Since different wares have distinct washing requirements, operators must determine what they intend to wash in order to specify the correct unit. Also, they should take into account the warewasher's design.
  • Verify capacity or throughput. Compare the ratio of usable cubic inches of wash area versus the unit's overall footprint.
  • Consider the costs associated with the many consumables related to warewashing, such as detergent, rinsing agents and other chemicals.
  • Evaluate energy consumption and water usage.
  • Examine the placement of the water jets to get a better picture of the wash action consistency.

Specifying Mistakes to Avoid

  • Not taking into account the space constraints for this equipment. It may be best to purchase a unit that is larger for increased efficiency, flexibility and capacity at peak periods and for future expansion of the operation.
  • Not considering the working space around the machine. A large, fast machine will be inefficient if the staff cannot load or unload it fast enough to make use of its capacity. Space needs to be allocated to drop off soiled items, scrape and load them, and for unloading clean ware.
  • Neglecting to confirm the durability of items the unit will wash. If a warewasher does not provide a gentle cycle, it will add significant premature wear to the items being washed, or shorten service life, making it costly to operate in the long run.

New & Notable Features

  • Most recent dishwasher innovations are associated with a reduction of rinse water and energy consumption. This includes dual rinse zones for improved results and reduced water consumption; heat recovery systems that reclaim the waste heat generated by the machine as a source of energy to preheat the incoming final rinse water, reducing energy consumption and machine emissions; and systems that actively reduce soil contamination in the wash water.
  • An airflow management system can dramatically reduce both the exhaust volume and its moisture content, reducing or eliminating the need for an external ventilation system (subject to local code requirements).
  • Improved washing dynamics through computational fluid modeling and increased wash pressure provide a 33 percent reduction in water, energy and chemical consumption.
  • Increasingly, high-tech features are being built into warewashers. For example, handheld computer interfaces can communicate with and control single or multiple warewashers. These interfaces can perform functions such as start-up, timed cycle selection and machine shutdown. Digital displays verify the machine status and temperature, and can be programmed to notify users about low temperatures, dirty water and excessive lime buildup.
  • Since health codes typically require dishes coming out of a warewasher to reach and maintain a specified surface temperature, manufacturers offer sensors that can extend a wash cycle to ensure such temperature is attained.
  • A relatively new technology is ventless warewashers, which can negate the need for exhaust hoods.

When to Replace

  • Increased service calls and high repair costs: When a unit requires an increasing number of service calls or multiple component replacements, it may be nearing the end of its service life.
  • Signs of wear and tear: Tank leaks may signify that the welds are giving out. Also, problems can be caused by water leaking from the boosters.
  • Loss of controls: If the warewasher's controls are not operating properly or pump pressure is lost, replacement is most likely appropriate.
  • Inconsistent results: The results of the unit are a key indicator that the warewasher is not operating at 100 percent.
  • Older models: Operators may want to replace older warewashers that are utilizing excessive amounts of energy and/or water with a more efficient unit.

Maintenance Musts

  • Clean dish machines after every shift, since flushing out the water removes accumulated soil from the machine, improving washing performance.
  • Regularly wash and clean scrap screens or filters.
  • Depending on usage and water quality, wash and rinse arms should be cleaned weekly or as required.

Environmental Advancements

  • Heat recovery systems capture heat coming out of the warewasher and redirect it out of the space and/or repurpose it as a heat source for the unit.
  • To conserve energy, many current conveyor-type machines only operate the wash pumps and final rinse when ware is actually in the appropriate zone of the machine.
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