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Water Quality Answers

What general procedures should be used with household dishwashers?

In any case, the instructions of the dishwasher manufacturer should be followed.  However, these may be supplemented with the following general considerations.

Avoid the use of sudsing soaps or synthetic detergents as the suds which develop can "muffle" the spray action used in most dishwashers to provide scrubbing action.  A number of washing compounds are on the market which have been specifically formulated for dishwashers.  These materials do not generally contain any soap - they depend upon the presence of greases and oils on the dishes to produce a cleaning solution.

Even with the use of soft water, spotting of dishes is sometimes reported.   In some cases, the cause may be traced to the use of too much washing compound.   In other cases, the dishwasher is loaded too heavily, and improper cleaning occurs.

Another common cause of spotting is too rapid drying.  Ideally, the dishes should first be allowed to drain completely in a humid atmosphere so that the water with its minerals runs off, rather than evaporates.  In some cases, the water temperature is too high, and the water evaporates rather than drains.  In other cases, the dishwasher lid opens at the end of the cycle and allows cool air to contact the utensils.  This too, results in rapid evaporation.

Dishwasher etching is the deterioration by chemical change on the surface of glassware caused by the action of high temperatures and excessive dishwasher detergents.  Etching is caused by the strong phosphate sequesterants (e.g., trisodium phosphate) in dishwashing detergent.  But it may be triggered by the combination of extremely hot water, soft water, and too much detergent.  The high water temperature can cause the detergent phosphate compounds to break down into an even more aggressive form.  If hardness is available, it will consume the most aggressive of these sequestering chemicals.  Otherwise, however, the detergent agents can actually extract elements directly from the glassware composition.  The solution to etching is to use less detergent and water temperatures less than 140o F when you have soft water.  Water softening is such an enhancement that the dishes will get cleaned just as well with less detergent and 120o – 140o F water in softened water.

Depending upon the construction of the dishwasher, it may be possible to adjust one or both of these factors to improve the results significantly.