It's a Wash

Dan Bendall

OVERLOOKED YET IMPORTANT. Sometimes dishwashers don’t get noticed until there is a warewashing problem. <em>(photo: Hobart)</em>

The dishwasher is one of the most important and also one of the most expensive equipment items in your kitchen. However, it doesn't get nearly the attention it deserves in the purchasing decision. It is certainly not a glamorous piece and not one chefs rave about. Although a customer may not appreciate its service either, they will surely feel its effect if the machine is not functioning.

Not only does the dishroom take up a lot of space in your kitchen, its centerpiece, the dishwasher, is one of the most expensive single pieces of kitchen equipment you'll ever buy. You will spend $10,000 for even a small upright single rack machine that can serve a restaurant of up to 100-120 seats. Medium sized restaurants over about 120-130 seats need a rack conveyor machine. One of these dishwashers may cost up to $20,000 and more depending size, number of tanks, and accessories. After you add in a clean dish table, soiled dish table, final rinse booster heater, and a few dish dollies and racks, it is not uncommon to spend $40,000 or more. Since the dishroom contains a sizable portion of your restaurant's overall equipment budget, it will pay to have a basic understanding of some of what is available on the market.

There are three basic types of dishwashers that are typically used in restaurant operations. Very small operations may be able to use an undercounter machine that generally has a realistic washing capacity of about 40 to 50 full place settings per hour. The commercial undercounter dishwasher looks, at first glance, quite similar to a residential style unit. The commercial unit however, is much more powerful and faster than its residential counterpart. Commercial undercounter machine cycles vary from the slowest machines that are just over three minutes to the fastest that are around 90 seconds. If you use a commercial undercounter machine remember that most local health departments require separate clean and soiled dish drain boards, separated to prevent cross contamination.

The next step up in dishwasher size is the door type or full height single rack machine. The machines wash and rinse a rack of dishes in a little over a minute. The rack machine can process about 90 to 110 place settings per hour and is suitable for a small to medium size restaurant. Over the last few years many manufacturers have paid attention to the tight space constraints in small to mid-size restaurants. Many now offer integral booster heaters to heat the final rinse water, and controls mounted within the footprint of the machine. The typical door type machine fits in a footprint approximately 24-30 inches square.

These compact units deliver a tremendous amount of washing power, some pumping over 150 gallons of recirculated water over the dishes during its short wash cycle. The machines being made today also conserve water in many cases, using well under a gallon of fresh water per cycle. Most manufactures make their door type units in either a straight through or a corner configuration.

Rack conveyor machines, the type that process dish racks continuously, are available in a wide range of capacity starting in size where the door type machines leave off and going up to several hundred place settings per hour. Most manufacturers make a wide array of conveyor machines that are based upon different combinations of standard modules.

All machines start with a basic wash tank and then add other modules that may be beneficial depending upon the specifics of your operation. For example, most manufacturers have one or two different pre-wash modules that are very effective for scrapping and removing heavy soil from dishware. Often the pre-wash temperature is lower than the wash compartment to remove rather than set protein soils like eggs.

Using a pre-wash also helps effectively use detergent by not introducing it until heavy soils are removed from the china. A pre-wash unit typically adds in the magnitude of $5,000 to the price of a basic conveyor machine, but is a significant aid in getting especially those dishes with heavy soil clean.

The next step up to higher capacity and better performance is the addition of a rinse tank or an extended wash tank. Without a rinse tank to recirculate rinse water, machines typically use more water than those with a recirculating rinse. All machines have a fresh water final sanitizing rinse. Conveyor machine lengths range in size from 44" to about 10'. The rack conveyors can also be built in a circular configuration that is convenient for some high volume operations. The scrapping area dishmachine and clean dish drying area is all constructed together in one unit with a continuous loop belt.

Flight type machines are a fourth dishwasher style. Flight machines differ from their conveyor counterparts in that dishes are loaded directly onto pegs built into the machine. Flight machines are generally used in institutions and extremely high volume operations with mass feeding requirements.

The amount of dishes to be washed will be the major factor in determining the type of dishwasher to purchase. When you look at machine capacities you first need to understand and decode the manufacturer's ratings. Most manufacturers advertise the capacity of their machines by the number of racks per hour it can handle based on their NSF (National Sanitation Foundation) listing. While the ratings are not meant to deceive, do not be fooled by these theoretical capacities. The ratings for door type machines that are typically about 40 - 60 racks per hour and start at 200 racks per hour for conveyor machines can be misleading. These numbers are computed mathematically and are not based on actual machine operation that must allow for loading and unloading the machine.

A typical rule of thumb is that the actual production of a machine in racks per hour is about 70% of the manufacturer's rating. In other words, if a machine is rated at 200 racks per hour you should expect to be able to wash about 140 racks per hour assuming you have a constant volume of dishes to be washed. The same is true for manufacturers' claimed capacity of dishes per hour. The actual dishes per hour may be even less than 70 percent since the claims are usually based on a relatively small dish or glass size that fits a 20" × 20" rack optimally.

Once the size and style of machine has been determined, there are several other initial purchase decisions to make. Energy efficiency needs to be considered. As if it isn't enough that dishwashers are very expensive and take up a lot of floor area, they are also energy hogs. Dishwashers are typically the single biggest energy and water user in a restaurant.

A standard dishwasher uses super heated 180° F water to sanitize dishware. There are also low temperature or chemical sanitizer machines that use chemicals to sanitize dishware. These machines are not for all operations. A benefit of the high temperature final rinse is quick drying of dishware and low energy consumption. High temperature machines are also better able to break down animal fats and grease as well as lipstick on glassware and dishes. Most chemical sanitizing machines use sodium hypochlorite (bleach), in lieu of 180° F water to chemically sanitize items being washed in the machine. It is critical to note that certain materials, including silver, aluminum, and pewter, are attacked by bleach and cannot be washed in a machine set up for chemical sanitizing.

Reduced energy and water consumption is important to everyone. Manufacturers have developed some substantial new technology to cut energy and water usage. One of the biggest introductions is new final rinse nozzles that create a spray pattern that provides dish coverage using less water. Other new provisions like insulated wash and rinse tanks are becoming more popular as energy prices soar.

For more on energy consumption, you can look at the Energy Star web site.

Dan Bendall is a principal of FoodStrategy, a Maryland-based consulting firm that specializes in planning foodservice facilities. A member of Foodservice Consultants Society International (FCSI), Bendall can be reached at 240-314-0660.