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Buying The Right Commercial Dishwasher

By Greg McGuire

Deciding on the right dishwasher for your restaurant or commercial kitchen depends on a few important factors, and it's vital to get the right machine for the job.

There are multiple types of dish machines depending on what you plan to wash and how much of it you plan to wash in a given day. The most common washer types are:

Undercounter - these dish machines are similar to residential models and can handle up to 35 racks per hour. They usually use a built-in heating element to flash heat dishes and ware to 180 degrees Fahrenheit for sanitization.

In Sink Glasswashers - these washers are for the quick washing and rinsing of glassware and are most commonly used in bars. They fit into a bar sink and have a rotating brush set in hot water to scrub used glasses. Glasswashers are manually operated and therefore cannot handle very high dishloads.

Door Type - these washers are larger than undercounter models and can handle up to 150 racks per hour. Door type washers are most commonly used in most restaurants. They have a large door that opens and allows racks to be easily moved in and out. Some models even have a conveyor that allows the constant processing of dish racks.

Conveyor and Flight - these washers are for high volume applications like cafeterias or institutions and can process over 400 racks per hour.

Booster Heaters - these stand-alone units pre-heat water to the NSF required 180 degrees Fahrenheit for proper sanitization. They operate independently of the dish machine and insure that enough hot water is available for washing. Booster heaters are typically used on large Conveyor or Flight dishwashers that process large volumes of dishes per hour. Most undercounter and door type units have a built-in booster heater. Check before you buy any dishwasher to see if you'll need a booster heater or not.

Choosing the Right Unit

Selecting the right dishwashing unit depends on the amount of dishes you need to wash in a given hour and the what you are washing. Some units are specifically designed to only wash glassware or pots and pans, and if your commercial kitchen has the space, it might be a good idea to split dishwashing tasks between two specialized units.

You also need to account for volume. Keep in mind that when you are calculating how many racks of dishes you produce per hour, you should use the number produced at times of peak demand.

Don't forget about future growth and seasonal trends! A dishwasher should last at least 5 years, and hopefully in that time your business will be growing as well, meaning more dishes to wash. Certain times of year can also be much busier. Make sure the dishwasher you buy can handle these peak dishload times.

On the other hand, the larger the unit, the more energy and water it consumes, and if dishes are processed too quickly then racks tend to go through half empty, resulting in inefficient operation. Make sure you take the time to accurately calculate dishload and select the right sized dishwasher. The following chart is a general guideline:

Meals/hour Washer type Max racks/hour
Up to 100 Undercounter 35
100-500 Door 125
500-2000 Conveyor 450
2000+ Flight 1000

Energy Efficiency

As energy and water costs continue to rise, selecting an energy efficient dishwashing unit has become more and more important to restaurants and commercial kitchens. Most commercial dishwashers employ automatic fill and idle pump shutoff features, as well as a built in booster heating unit to improve energy efficiency.

Energy Star, a government run agency, now rates commercial dishwashers for their energy efficiency. Energy Star rated units will operate more efficiently than non-rated ones, so look for the Energy Star label when you're buying a commercial dishwasher.

High Temp vs. Low Temp

High temperature dishwashers:

  • Use heat to sanitize dishes and glassware
  • Must achieve 180 degrees Fahrenheit to meet NSF regulations
  • Use slightly more energy than a low temp dishwasher
  • Do not require the regular purchase of chemicals
  • Do not damage flatware and plastics
  • Is the most commonly used commercial dishwasher

Low temperature dishwashers:

  • Use a chemical bath to sanitize dishes and glassware
  • Are not as effective at removing grease
  • Are slightly more efficient than high temp models
  • Can damage flatware and plastics
  • Require you to purchase chemicals on a monthly basis

Some argue that the cost of chemicals for a low temp dishwasher is much less than the increased energy savings versus a high temp unit. While this may be true, the main factor to consider when you are trying to decide between a low or high temp dishwasher is the damage to flatware, plastics, and dinnerware that might occur with a low temp model because of the sanitation chemicals used.


The proper ventilation of the dishwashing area in your commercial kitchen or restaurant is very important, and not just for the safety and comfort of staff. High humidity reduces the effectiveness of your dishwasher's drying cycle, and is usually why dishes come out of a commercial dishwasher damp. Good ventilation for the dishwashing area in your kitchen is strongly recommended.

Preparing Dishes For Washing

Food bits and other debris should be removed from dishes to maximize the effectiveness of your dishwasher. The most efficient way to accomplish this is to use a pre-rinse assembly. Pre-rinse assemblies are a powerful spray nozzle mounted on a free swinging, upright hose. Kitchen staff simply depress a lever and wash down dishes before they go into the dishwasher.

Dishes should also be stacked into a dishrack to maximize their exposed surface area so they can be cleaned effectively. Most commercial units are designed to accommodate a standard full size 20" x 20" dishrack. Half racks are also available for smaller units. Dishwashing racks come in a few standard types:

  • Peg racks hold dinnerware, pots, pans, and lids upright for washing
  • Flat racks are ideal for washing flatware and have a flat bottom made of tight lattice to prevent pieces from falling through
  • Flatware baskets are half rack sized and hold flatware upright for washing
  • Glass racks have multiple compartments for glassware and optional extenders that allow you to stack rows on top of each other

Some other useful dishrack accessories include a dolly for convenient moving of stacked racks and a dishrack hold down grid that fits into a rack and prevents lightweight items from getting blown out by dishwasher jets.

Scale Inhibitors

A scale inhibitor is a type of water filter that removes minerals and sediment from tap water. These elements in the water build up in the dishwashing unit, increasing the likelihood of maintenance problems and shortening the unit's life. Unfiltered water also leaves streaks and spots on glass, dinnerware, and flatware.

Greg McGuire is a regular contributor to The Back Burner, a restaurant news, trends, and marketing blog. He also works for, a company specializing in restaurant equipment, supplies, and equipment parts.

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