Over the past year we are seeing a steady growth in all-in-one dishwasher detergents. These products not only work as a detergent, but also perform the functions of rinse aid and/or dishwasher salt.
These can be found in liquid or tablet form, and their characteristic is to contain ingredients that, under normal water hardness conditions, are able to keep the limescale dissolved, thus making the rinse aid and salt unnecessary.
This feature makes all-in-one products particularly convenient and also cheaper, since they make it possible to avoid buying salt and/or rinse aid.
The result of all-in-one products is satisfactory in areas where the hardness of the washing water is soft or medium-hard. On the other hand, if you are in an area where the water hardness is high (above 25° French degrees), it is very likely that dishwashing detergent alone will not be sufficient to ensure an adequate shine for dishes and glasses. In this case it is advisable to add rinse aid and adjust its dosage to the minimum.
However, you will only be able to realize the actual need to add it after a few test washes. In particular, above 35° French degrees it is definitely necessary to add salt to regenerate the softener resins and counteract the action of very hard water.
You can find the water hardness of your area online at the website of your local water utility.