Water Hardness Test Strips, the hardness of water depends on its content of calcium and magnesium salts. When measuring the total hardness, the sum of these salts is determined. It is expressed in mmol/l or in the older common unit degrees of hardness, whereby it is important to differentiate between German, English and French interpretation:
•Iin Germany: 1 °d = 10 mg/l CaO = 17,8 mg/l CaCO3
•iIn Great Britain: 1 °e = 14.3 mg/l CaCO3
•iIn France 1 °f = 10 mg/l CaCO3 Conversion factors: 1 °d = 1.25 °e = 1.78 °f = 0.178 mmol/l
•IIn the USA, the water hardness is simply expressed in terms of mg/l CaCO3 . Apart from the above values, water is often simply classified as "soft water", or "hard water" etc.
The following values generally apply to these terms:
•below 90 mg/l CaCO3 - very soft water
•90 - 180 mg/l CaCO3 - soft water
•180 - 270 mg/l CaCO3 - medium hard water
•270 - 450 mg/l CaCO3 - hard water
•above 450 mg/l CaCO3 - very hard water
The hardness of water is often of importance where no laboratory facilities for the analytical determination exist. In these cases the Water Hardness Test provides a quick method for an indicative reading. Its sensitivity is adequate for textile establishments of moderate size, in dyeing, laundries, small water works, boiler rooms as well as in pisciculture, aquaria and also for household use. Sensitivity: The Water Hardness Test allows the determination of the water hardness from 0 to over 21 °d, i.e. up to about 540 mg/l CaCO3.