Dishwashers

Dishwashing in commercial, industrial, and institutional kitchens offers another opportunity to save water. Many of the water saving measures that can be used in these applications are the same as those used in residential applications. Past studies have shown that industrial kitchens can achieve water reductions of approximately 15 percent through process modifications alone (North Carolina DENR, 1998).

For smaller operations where a residential dishwasher provides adequate dishwashing capacity, managers should seek out the U.S. Environmental Protection Agency's (EPA) ENERGY STAR qualified dishwashers. These dishwashers use at least 41 percent less energy than the federal minimum standard for energy consumption, and significantly less water. The EPA estimates that replacing a dishwasher manufactured before 1994 with an ENERGY STAR qualified dishwasher can save more than $30 per year in utility costs ENERGY STAR).

For larger operations, there are four main types of dishwashing machines for commercial and industrial kitchens: undercounter, door, conveyor, and flight. A wide array of models and accessories are available for each category. Requirements for machine size can be calculated by estimating the amount of traffic that will be served in a facility's food service area. Most dishwashers use between 2.0 and 7.0 gallons per minute (gpm) for a complete cycle of cleaning and sanitation.

• Similar to residential undercounter dishwashers, undercounter machines for commercial, industrial, and institutional applications use the most water per rack of all commercial dishwashers. If you use one of these systems, wash only full racks when the machine is in use to conserve water. Such systems are best suited for food operations that serve less than 50 people.
• Manufactured to service 50 to 200 people, door type machines are the most widely used commercial dishwashing machines. Some door type machines now have the ability to recycle rinse water to be used again in a wash cycle.
• Most widely used in hotels, large restaurants, hospitals, schools, and universities, conveyor rack machines are well suited for service of 200 or more people, accommodating most heavy food service operations. Water efficiency measures, such as the installation of an electric eye sensor (that keeps the conveyor from running when there are no dishes on the racks) can make rack conveyors more energy- and cost-effective. Look for the most efficient conveyor models, which can reduce final rinse consumption from 300 gallons per hour (gph) to 130 gph. The use of energy efficient boosters and low flow pumps can reduce energy and water consumption levels by 50 percent.
• Similar in that they use a conveyor belt to move dishware, flight type machines do not have racks. Rather, dishes are loaded directly on to a belt. Flight type dishwashers provide high volume washing capability needed only in the largest institutional, commercial, and industrial facilities. Variations in possible machine additions include power scrapers, power wash, power rinse, final rinse, and blower dryers. Water efficient strategies for these machines include the recirculation of final rinse water, electric eye sensors, extra-wide conveyors, and low-energy built-in booster heaters. These additions have amounted to water savings of as much as 47 percent, while maintaining loads of more than 14,000 dishes per hour.

Other strategies for saving water and energy include the following:

• Look for models with door switches for convenient on/off access.
• Check the rating of any booster heater used to make sure it fits the machine.
• Use dishwashers with steam doors to prevent loss of water due to evaporation.
• Install low temperature machines that rely on chemical sanitizing over high water temperature.
• Verify your volume of service and estimate facility needs. A better option may be a larger machine that has a lower water flow rate per rack.

References

North Carolina Department of Environment and Natural Resources (DENR), North Carolina Division of Pollution Prevention and Environmental Assistance, North Carolina Division of Water Resources, and Land-of-Sky Regional Council - WRATT Program. 1998. Water Efficiency Manual for Commercial, Industrial, and Institutional Facilities. Authors, Raleigh, NC.