Warewashing & Dishwashing Information

Manual vs. Machine Warewashing

Although many of you probably don't sit up all night wondering whether manual warewashing actually costs less than using a dish machine, you have probably been asked to justify the cost of automated warewashing. How do you answer? is there a cost benefit to washing with a machine? What is the real cost difference between the two processes?

Three-compartment sinks are a commodity item and can be purchased with all the faucets and drains from $1,500-$3,000 depending on size and quality. A proper dish machine setup can easily double or triple the cost of a Three-compartment sink. But which costs less?

A typical Three-compartment sink has three equal-sized bowls; each using about 40 gallons of hot water when filled properly. Every time you fill the unit, you use about 120 gallons of hot water. Typical operators need to refill the sinks every 2-4 hours, depending on how difficult the utensils requiring washing are to clean and the amount of soils and fats introduced into the sinks. If they do not refill periodically, they leave the hot water running continuously over the sinks in order to keep the water hot. Cleaning requires HOT water.

If a restaurant serves three meals a day and is open for 16 hours, you can expect them to consume anywhere from 480 and 960 gallons of hot water a per day. National average cost to buy, heat and use water is about $0.008 per gallon. It will cost the operator $4-$8 per day in utilities to operate a Three-compartment sink.

It also takes at least one employee a minimum of two hours to wash, rinse and sanitize dishes and wares for every meal period. The average labor cost for this position in a restaurant is about $8 per hour, including wages and benefits. A typical restaurant spends about $50 a day in labor costs to complete the three-step cleaning process.

In total, it costs an operator $54-$58 per day in labor and utility costs to use the Three-compartment sink, or about $20,000 annually. This cost does not include the cost of chemicals used in the sinks.

A dump and fill-style CMA dish machine uses two gallons of water for every rack cycle. In a typical 90-second dish machine, the operator will use 70 gallons of water per hour. During this 90-second cycle, the dish machine automatically washes, rinses and sanitizes dirty wares and utensils for approximately four (4) persons, or 140-150 people per hour. The capacity of the dishwasher exceeds the demand of a typical operator needing to handle the dirty wares created by serving 100 meals each meal period.

The time to wash the same amount of dishes in a dishwasher rather than a Three-compartment sink is half! In our example, the six hours it took in the Three-compartment sink is cut to just three hours per day. With this efficiency, the utility cost for the dish machine is less than $2 per day (including a pre-rinse water used before placing the rack in the machine) and the labor is about $24 a day. This total daily savings of about $38 a day saves the operator $14,000 a year.

However, there is an additional cost in operating the dishwasher. The cost of running the wash motor is about $0.14 per hour using national electricity rates. This equates to $0.40 per day or $150 annually in additional electrical charges. (Note: Novelty sinks that incorporate motors or heating systems into a three-compartment sink can make manual washing easier. However, these features add to the cost of operation and do not reduce the time or water it takes to complete the job).

There are other benefits to machine washing. Because the machine uses less water than manual washing, it uses proportionately fewer chemicals. Dish machines also dispense exactly the same amount of detergent and sanitizer every cycle, assuring consistent results and managed chemical usage. More importantly, it also ensures proper sanitation every single time!

Who enjoys doing dishes by hand? Dish machines improve employee morale. It also allows the person operating the machine to perform multiple tasks at the same time. In smaller operations, it reduces the amount of time spent in the kitchen and allows employees more time to focus on important matters, such as customer service.

After considering the true cost of operating Three-compartment sinks and dish machines, the lower price of the Three-compartment sink ends up more expensive than the overall cost of the automatic warewashing. True costs include the equipment cost plus the operating cost involved with the entire process.

Chemical Sanitizing vs. Hot Water Sanitizing Dishwashers

Conventional high temperature rinse sanitizing dish machines can consume up to one-third the energy used in many operations. How is this possible? During the winter, ground water temperature can drop to 40 degrees F. This cold ground water must be heated to 150-160 degrees F initially to comply with National Sanitation Foundation (NSF) wash tank requirements, and then to 180 degrees F to comply with NSF sanitizing rinse requirements. At normal rated flow pressure of 20 pounds per square inch (psi), the common single-tank conveyor dish machines rated around 200 racks per hour will consume about 300 gallons per hour of water.

During a typical hour of operation, a 525,000 BTUh input gas or 125 KW electric primary hot water heater will have been in operation, a 1 or 2 horsepower wash pump will have been pumping, a 45 KW electric rinse booster heater will have been boosting the primary water to 180 degrees F, a 10 KW to 15 KW wash tank heater will be helping to keep the wash tank water between 150-160 degrees F.

In an all-electric operation, with electricity costing only $0.08 per kilowatt-hour, that hour's worth of continuous dish machine operation would cost 165 KWH x .08/KWH or $13.20. This analysis doesn't consider the heat loss from uninsulated water pipes, air-conditioning costs and motor operations.

Some Solutions and considerations:

1. Automatic machine shut-off: How often have you entered the dish room and observed the automatic, rack conveyor machine merrily pumping away without a dish boy anywhere to be found? Although probably not consuming rinse water, other system components such as fan, wash pump, and tank booster are consuming their normal quota of BTU's or KW's. Utilizing an automatic machine shut-off that causes the dish machine to stop when the rack is not introduced into the machine after a specific period of time provides a low cost improvement to the existing rack conveyor machine. It can interlock a start switch with the wash pump, exhaust fan, wash and rinse boosters. Manufacturers that offer this feature will help reduce conveyor machine operating time significantly with resulting savings in energy
2. Proper machine sizing: An inherent disadvantage of the conveyor dish machine is its ability to "overkill." As discussed previously, it is possible for such a machine to run when no racks of dishes are being washed. This problem can be controlled or eliminated when using a machine with the auto shut-off feature. What is more difficulty to control, however, is running less-than-full racks through the machine.
   
   A good solution may be to "take a step backward" and utilize a door-type dish machine instead of the conveyor. If your operation does not need the capacity to handle over 200 racks (probably partially full) of dishes, why not consider a machine capable of doing 40, 50, or even 80 full racks instead? the door-type dish machine significantly reduces energy costs and have a maximum consumption of only 90-150 gallons of water per hour.
3. "Low-temperature" dish machines: Do low-temperature dish machines perform as well as high temperature dish machines? Yes. Are they NSF approved? yes. Any "tricks of the trade?" Yes. Any application restrictions or consideration? Only a few. How do they differ from "high-temperature" machines? Great question!
   
   The primary difference between the operation of a low and high temperature dish machine is the way in which they sanitize dishes. During the final rinse portion of the machine cycle, low-temperature machines utilize a chlorine-based sanitizer while a high temperature machine uses 180 degrees F hot water to kill bacteria. Either method is an effective way to kill bacteria.
   
   Both low and high temperature dish machines need hot, soft water to wash dishes. Although NSF requires low-temperature dish machines only need be provided with a minimum water temperature of 120 degrees F, we recommend 140-150 degrees F incoming water temperature to ensure excellent results.
   
   Many low-temperature machine installations rely on the customer to provide continuous hot water from their hot water supply. If the customer is unable to provide a constant supply of 140 degrees F hot water, then we suggest installing a small booster heater capable of maintaining a continuous supply of 140 degrees F hot water to the low-temperature dish machine.
   
   Capacity-wise, low-temperature dish machines are virtually identical to their high-temperature counterparts. The true benefit lies in the overall operating cost of the equipment. Using the same $0.08 cost per KWH previously, the cost to operate a low-temperature machine (even with a 10KW booster heater attached) is approximately $2.75 per hour. there is over a $10.00 per hour savings at the same capacity as a high-temperature dish machine. What a savings when you realize a typical operation operates their dish machine over four hours per day. When annualized, this savings can be as much as $15,000.

Application considerations, myths & facts

Myth: Dishes don't dry as well in a low-temperature dish machine.

Fact: Most of the heat is placed into the dish during the 140 degree F wash cycle. this doesn't differ between high and low-temperature machines. The 180 degrees F rinse actually adds very little heat to air drying.

Fact: Most drying problems are caused by excessive relative humidity in the dish room. Adequate ventilation is necessary even with a low-temperature dish machine. 140 degree F water is still pretty hot and humid.

Fact: Because dishes being removed from a low-temperature machine are slightly cooler, many operators immediately stack them together before they are completely dry. This impedes the drying process.

Fact: Precise controls of wash and rinse temperature is important. Temperatures below 10 degrees F will not effectively remove animal fats from dishes and will take longer to dry; temperatures above 150 degrees F tend to drive the chlorine sanitizer out of solution. Optimum wash temperature is between 140-150 degrees F.

Caution: Wash temperatures exceeding 160 degree F can actually begin to "bake" product back on to the plates.

Myth: Low-temperature machines increase chemical costs.

Fact: Because of the reduced water flow chemical usage may actually be less. Plus the cost of chemical sanitizer is extremely low. NSF only requires 50 ppm of chlorine-based sanitizer to be introduced into the final rinse phase of the wash cycle.

Caution: Chlorine-based sanitizers can attack or discolor metals such as silver, aluminum or pewter.

Myth:Low-temperature machines use more water than high-temperature machines.

Fact: Conveyor-type dish machines use virtually the same amount of water.

Fact: Door-type, low-temperature machines can use up to 2 gallons of water per cycle, where as, high-temperature machines use about 1 gallon per cycle. However, high-temperature machines are required by health department regulations to change the water in their tanks every two hours. These wash tanks range from 15-40 gallons and must be added to the overall consumption of the high-temperature machine in order to get an accurate water consumption figure. Generally, you will find the water consumption for each style machine to be a "wash."

Fact: Because low-temperature machines dump all the water after each wash cycle, most of the soils and fats are removed as well. High temperature machines have difficulty removing heavy soils and fats from their large tanks.

Additional comments:

• Fill and dump machines have one set of pumps, nozzles, controls, etc. This generally means fewer things to go wrong and they are easier to service.
• Good pre-scraping is absolutely necessary with any style dishmachine.
• Low-temperature (door-type) machines do not rely on water pressure during the final rinse. they use a pumped rinse system that is more consistent and reliable.
• Without adequate training, proper procedures and maintenance, no machine will function properly.
• Every cleaning procedure needs TACT. In the case of washing dishes in a dish machine, TACT stands for Temperature (140-150 degrees F), Agitation, Chemical concentration & Time.