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Water Hardness

Hardness in water is a measure of the concentration of Calcium Carbonate (CaCO3) in the water. It appears in the form of scaling and deposits in kettles. With high concentrations, there sometimes appears to be an “oily film” on the surface of beverages (tea in particular). This is a thin film of limescale and is harmless.


The water in most of Fingal originates from the River Liffey and could be considered mildly hard. The water supply in the Balbriggan area of Fingal is supplemented by a ground water scheme that is considered hard water. All water supplied in Fingal complies with the Drinking Water Regulations.


The following table summarises the various hardness scales that are described in Dishwasher Handbooks and the typical values in different parts of Fingal.

Hardness Scale            Most of Fingal Balbriggan Area
Mg/l of CaCO3                    200                  350
Clarke or English (° eH)       14.6                 25.6
German (° dH)                     11.3                 19.7
French (° fH)                        20                    35
American (ppm)                  200                   350