Water Usage in Dishwashers

commercial dishwasher

Water Usage in Dishwashers

Water usage in dishwashers is one of the highest wastes of water and energy in restaurant and hotel kitchens. It is estimated that they consume two-thirds of all water usage.

Dishwashers may use single or multiple washing tanks. Some types use hot water (high temp machines) or cleaning chemicals with cold water (low temp machines) in order to achieve the required level of sanitation.  Interestingly, high temp machines are more water efficient than low temp models.

Types of dishwashers:

Under-counter units are the smallest type.  These units use a revolving wash arm with a small holding tank. Traditional under-counter units can use up to 1.8 gallons of water per rack. High efficiency models use only 1 gallon per rack.

Stationary rack type dishwashers are larger. These are the most common type of dishwashers and are used in most restaurants and hotels. These machines use vertically-sliding doors for loading and unloading dishes, and two revolving spray arms for even water distribution. Typical units consume up to 2.2 gallons per rack, while high efficiency models consume 0.95 gallons per rack.

The rack conveyor is the largest. These units are popular in large restaurants and hospitals. The units utilize a motor-driven conveyor belt to pass the rack through a washing tank. The washing solution is maintained in a single tank at a fixed temperature. The solution is pumped through multiple spray arms once the machine is running, regardless of the presence of dishes. The racks are then sprayed with hot water (82°C) for a final rinse. Although they are large units, typical rack conveyor machines consume up to 1.2 gallons per rack. High efficiency models can consume as low as 0.54 gallons per rack.

When you take these figures into consideration, it’s easy to see how important it is to pay attention to the water usage in commercial dishwashers.

Steps to take:

If you are in the market for a new dishwasher, consider purchasing an Energy Star-Certified appliance. These high efficiency units can save as much as 25% on water and energy consumption. The savings in utility bills can reach $975 for electricity and $200 for water charges annually, according to the U.S. EPA Energy Star Program.

If you already have an existing commercial dishwasher, you can still implement smart measures to decrease water and energy usage without compromising cleanliness and sanitation. The first step is to educate kitchen staff to run the dishwasher only when full. A typical commercial dishwasher can clean 540 plates per hour.

Another measure is controlling water pressure. If you don’t have a pressure gauge on the inlet water line to the dishwasher, have one installed. Normally, 20 psi is considered adequate water pressure for most dishwashers. However, if pressure is in excess of 25 psi, then the machine may be using more water than necessary.

If you own a rack conveyor model, make sure to run it in auto mode, which saves electricity by running the conveyor only when needed. Also, regularly check the temperature gauge on the machine that it does not exceed 82°C (180 F). If the temperature is consistently higher than that, you are unnecessarily wasting energy.

If you have hard water, then consider installing a water softener. A softener removes hardness ions (Calcium and Magnesium) from water and significantly reduces scale deposits on the heating element. This will maintain high heat transfer efficiency and reduce electricity usage.

With these practical measures, it is possible for restaurants and hotels to reduce water usage in commercial dishwashers without compromising cleanliness, sanitation, and quality of service to customers.

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