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Understanding Automatic Dishwashing

Automatic dishwashers represent a tremendous saving in time and effort; they minimize breakage through reduced handling of dishes; they help keep the kitchen neater and more clutter-free; and cleanup after entertaining is simplified. These are benefits that have much appeal to consumers.

In order to ensure that public health standards are maintained, hospitals and many other food service institutions are required by law to clean dishes by automatic dishwashing methods.

The benefits of an automatic dishwasher and the specially formulated detergents can only be realized if they are used correctly. It is, therefore, important for the user to understand how the dishwasher works, the purpose of its features and how to load and operate it properly. User's manuals and detergent packages contain this information.

 The Dishwasher

The function of the dishwasher is to provide the mechanical action necessary to distribute and direct the detergent solution and rinse waters over, under and around the dishes to loosen and remove soil. The dishwasher must also remove soil-laden waters from the machine after each phase of the cycle and provide for the drying of dishes after the cleaning process has been completed.

Washing Systems

Automatic dishwashers vary in the design of their washing systems (or the means by which water is distributed). Some have a single water source, others may have several water sources. Water is distributed in dishwashers by spray arms or spray towers (or in the case of some older models by an impeller). The design of the spray arms or towers may differ in size, shape and placement in the dishwasher, or in the number, size and location of their water ports (holes through which water is forced). All of the washing systems do a good job, but those with fewer water sources require greater care in loading the dishes to prevent blocking the washing action to various parts of the machine, especially the corners.

The Water

The role of water is to dissolve and carry detergent, wet and loosen soil and effectively rinse the soil away. The velocity with which water is distributed in the dishwasher provides the scrubbing action to loosen and remove soil.


Cleaning in a dishwasher is accomplished with a relatively small volume of water. Contrary to what some people think, the dishwasher does not fill completely as does a clothes washer. The dishwasher, instead, employs several small fills during a cycle to accomplish the washing and rinsing operations. The total volume of water used in a complete cycle can vary from 6 - 10 gallons, depending on the number of washes and rinses included in that particular cycle.

Water pressure in a home may be noticeably reduced at some times because of numerous household water demands. As a result, insufficient water in the dishwasher could occur. This can be avoided by keeping bathing, laundering and other activities requiring quantities of water to a minimum while the machine is in use.


The temperature of the water is an important factor in dissolving detergent, removing food soils and drying dishes properly. To do these things most effectively, the water temperature at the dishwasher should not be lower than 130 degrees F (54.4 degrees C). As temperature is reduced, the removal of greasy and oily soils becomes more difficult; spotting and filming on dishes may occur as well as improper drying.


The amount of hardness minerals and other dissolved solids in water present obstacles to good automatic dishwashing results. Hardness minerals can cause spotting and filming on dishware. They must be effectively tied up or sequestered if the results are to be satisfactory. Hardness of water is determined by the amount of calcium and magnesium in the water. It varies from locality to locality and season to season. Water hardness is expressed in grains per gallon (gpg), parts per million (ppm) or milligrams per liter (mg/L)

  Soft Moderately
Hard Very
Grains per gallon 0.0 to 3.5 3.6 to 7.0 7.1 to 10.5 10.6 +
Parts per million or milligrams per liter 0.0 to 60 61 to 120 121 to 180 More than 180

To find out the water hardness in your area, call the local water company, public utility consumer service department or the home economist at the Cooperative Extension Service office.

The Detergent

Automatic dishwashers require detergents with very special characteristics because of the conditions under which the detergent must work. One of its essential characteristics is that it must produce little or no suds or foam because too much foam can inhibit the washing action. Other important functions that a dishwasher detergent should perform are the following:

  • Make water wetter (reduce surface tension) to penetrate and loosen soil.
  •  Tie up water hardness minerals to permit the detergent to do its cleaning job.
  • Emulsify greasy or oily soil.
  • Suppress foam caused by protein soils such as egg and milk.
  • Help water to sheet off surfaces of dishes, thus minimizing water spots.
  • Protect china patterns and metals from the corrosive effects of heat and water alone.


To accomplish these functions, the following ingredients may be included depending on the formulation and product form:
SURFACTANT (nonionic) _ lowers the surface tension of water so that it will more quickly wet out the surfaces and the soils. Lowering the surface tension makes the water sheet off dishes and not dry in spots. The surfactant also helps remove and emulsify fatty soils like butter and cooking fat. Nonionic surfactants are used because they have the lowest sudsing characteristics.
BUILDER (complex phosphates) _ combines with water hardness minerals (primarily calcium and magnesium) and holds them in solution so that the minerals cannot combine with food soils and so that neither the minerals themselves nor the mineral/food soil combination will leave insoluble spots or film on dishes. A builder helps maintain a desirable level of alkalinity, necessary for good soil removal.
CORROSION INHIBITOR (sodium silicate) _ helps protect machine parts, prevent the removal of china patterns and the corrosion of metals such as aluminum.
CHLORINE COMPOUND _ aids in sanitizing, helps make protein soils like egg and milk soluble, aids in removing such stains as coffee or tea and lessens spotting of glassware.
SPECIAL ADDITIVES (sodium aluminate, boric oxide, aluminum phosphate, etc.) _ may be used to inhibit overglaze and pattern removal from fine china.
ADDITIONAL ALKALIS (sodium carbonate, trisodium phosphate) _ may be used to aid in handling greasy food soils.
PERFUME _ covers the chemical odor of the base product and stale food odors which might otherwise emanate from the dishwasher.
PROCESSING AIDS _ generally inert materials that allow the active ingredients to be combined into a usable form.

A Specially Formulated Product

There are no substitutes for an automatic dishwasher detergent. Only an automatic dishwasher detergent can be used in an automatic dishwasher. These products come in either powder or gel form. All other types of detergents or soaps produce too much suds and will smother the water action necessary for cleaning in the dishwasher. Furthermore, enough suds might be generated to cause a dishwasher to overflow. This could necessitate a service call and could be damaging to the dishwasher and the floor around it. No other type of cleaning product such as baking soda, borax, vinegar or hand dishwashing liquid can be substituted for an automatic dishwasher detergent. These other materials will not perform well and may be damaging to the items being washed or to the dishwasher itself.


Enough dishwasher detergent must be used to soften the water effectively, suppress foam from food soils, provide the necessary cleaning and suspension of soil and protect materials being washed. Underuse will result in poor cleaning, redeposition of soil, spotting, filming and possibly damage to some items being washed. Both the dishwasher instruction booklet and the detergent package provide guidelines for proper usage. A good general rule is to fill the detergent dispenser cup or cups to the level recommended by the dishwasher manufacturer.

It should be remembered that water hardness in any area may vary from season to season and that more detergent may be needed at some times than is needed at other times.


Powder automatic dishwasher detergents readily take up and retain moisture and carbon dioxide gas from the atmosphere. Should this occur, the product may become lumpy. As long as it properly dissolves it can be used, but may be somewhat less effective. To help prevent this condition, the carton is specially designed to provide a moisture barrier. Consumers should open the package as directed, avoiding unnecessary tearing of the overwrap and closing the box after each use. Always select undamaged packages and purchase only one or two at a time to ensure maximum product effectiveness.


Store these products in a cool, dry place. Storage under the sink is not advisable because this area is generally too warm and moist to keep the product in optimum condition.

Rinse Agent

Some dishwashers have automatic rinse agent dispensers which release a liquid wetting agent into the final rinse cycle. Rinse agents in solid form are also available for use in dishwashers without the dispenser. The rinse agent allows the water to sheet off dishes rather than dry in droplets, thus helping to eliminate spotting. It is particularly helpful in hard water areas and when heat is eliminated in the dry cycle to conserve energy.

Safety Tips

  • Store automatic dishwasher detergent out of the reach of children, especially toddlers who like to taste and touch everything within their reach.
  • Never store automatic dishwasher detergent and other household cleaning products in low cabinets that are accessible to small children. An upper wall cabinet that is within easy reach for convenient use is safer.
  • Store all household cleaning products away from food products.
  • Keep automatic dishwasher detergent in original container.
  • Another child safety measure is to add detergent just before turning on the dishwasher. Return the product to storage shelf immediately.
  • On completion of the cycle, check to be sure that no detergent is left in the dispenser cups. Clean out if necessary.
  • When discarding containers, be sure they are empty and placed in a covered receptacle.
  • Hot water is essential to effective results in automatic dishwashing. To prevent possible burns and scalds, exercise caution, especially with young children, when hot tap water is being used in any area of the home.

Energy Saving Tips

  • Load dishwasher correctly for best results.
  • Use recommended amount of automatic dishwasher detergent.
  • Operate dishwasher only when a full load is accumulated.
  • Use shorter cycle if suitable for amount of soil on dishes.
  • Eliminate heat during dry cycle if water spotting is not a problem.
  • Run the appliance during off-peak hours.