The dishwasher is one of the most expensive equipment items in your kitchen, yet it doesn't get nearly the attention it deserves. The machine and its workspace can take up to one fifth of the area of your entire kitchen, and if there's a breakdown, your entire operation will be affected.
The dishwasher purchase decision is an important one in your equipment buying strategy. 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 (about 120-130 seats) require a rack conveyor machine, which can cost up to $20,000 and more depending on 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's not uncommon to spend $40,000 or more. Since the dishroom contains a sizable portion of your restaurant's overall equipment budget, it pays to have a basic understanding of what's available on the market.
There are three basic types of dishwashers. Very small operations may use an undercounter machine that 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, with cycles running just over three minutes, to the fastest, at 90 seconds.
By comparison, a residential dishwasher may take over an hour to complete a wash and rinse cycle. Do not try to use a domestic model in your commercial operation because it will not meet the strict sanitation codes required. If you use a commercial undercounter machine, remember that most local health departments require separate clean and soiled dish drain boards, to prevent cross contamination.
The next step up in dishwasher size is the door-type or full-height single-rack machine. These 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 have 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 more than 150 gallons of recirculated water over the dishes during the short wash cycle. In many cases, the machines being made today also conserve water, using under a gallon of fresh water per cycle. Most manufacturers make their door-type units in either a straight-through or a corner configuration.
Rack conveyor machines
This type comes in sizes where the door type machines leave off. They can clean up to several hundred place settings per hour. Most manufacturers make a wide array of conveyor machines that are based upon different combinations of several standard modules. All machines begin 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 prewash modules that are very effective for scraping and removing heavy soil from dishware.
Often the prewash temperature is lower than the wash compartment to remove rather than set protein soils like eggs. With a prewash, detergent is not introduced until heavy soils are removed from the china. A prewash unit typically adds $5,000 to the price of a basic conveyor machine, but is a significant aid in getting those dishes with heavy soil clean.
The next step up in 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 inches to about 10 feet. The rack conveyors can also be built in a circular configuration that is convenient for some high volume operations. The scraping area, dish machine and clean-dish drying area are all constructed together in one continuous loop belt.
Flight-type machines are a fourth dishwasher style but are generally too large for restaurants, so they will not be discussed in detail. 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.
So, which way do you go?
The amount of dishes to be washed will be the major factor in determining the type of dishwasher to purchase. Most manufacturers advertise the capacity of their machines by the number of racks per hour they 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 — which 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 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 percent 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 by 20-inch rack optimally.
Once the size and style of machine have been determined, energy efficiency should be considered. Dishwashers are the biggest energy and water users in a restaurant. A standard dishwasher uses 180°F water to sanitize dishware. There are also low temperature or chemical sanitizer machines that use chemicals to sanitize dishware. These machines have a place in the market, but they are not for all operations. You must weigh the cost of the sanitizing agent against your energy costs. Also, be aware that a benefit of the high- temperature final rinse is quick drying. High-temperature machines are also better able to break down animal fats, grease and lipstick on glassware and dishes. Most chemical sanitizing machines use sodium hypochlorite (bleach) in lieu of 180° F water to sanitize. Keep in mind that silver, aluminum and pewter are attacked by bleach and cannot be washed in a machine set up for chemical sanitizing.
Seek out new technology to cut energy and water usage. One of the biggest is final-rinse nozzles. These simple nozzles create a spray pattern that provides dish coverage using less water. The impact is incredible. Also, water booster heaters that used 50 kilowatts now use under 30. Along with the electrical savings, water consumption is cut to well under one gallon per rack. Insulated wash and rinse tanks are becoming more popular as energy prices soar. Heat reclaim systems are starting to pop up on machines as well.
For more energy savings look at the Energy Star web- site. Energy Star has just developed a category for dishwashers, which are on average 25 percent more energy-efficient and 25 percent more water-efficient than standard models. These efficiencies translate into about $1,000 in energy and water savings per year.
Dan Bendall is a principal of FoodStrategy, a Maryland-based consulting firm specializing in planning foodservice facilities. He is also a member of Foodservice Consultants Society International. He can be reached at 240-314-0660.