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Water Softener FAQ’s
What is soft water
Whilst the meaning of hardness is generally understood, the term ‘soft water’ is often subject to confusion. Soft waters are those which contain less than about 20 p.p. m. Ca2+ and Mg2+, and in many areas of Great Britain, such as the hilly regions of Wales and Scotland, these soft waters have very low total dissolved solids: indeed, the total of all ions may be below 50 p.p.m. As a result, it is not uncommon to find among non-technical water users in industry, a belief that all soft water, including those artificially softened, have a low mineral content.
The misconception that ion exchange softening gives results equivalent to those of distillation is still not unknown; and it is fairly common experience for a water treatment contractor to be asked to supply a softener, when a brief study of the proposed use of water shows that complete demineralising, that is, removal of all dissolved salts, is required.
A water source may, therefore, be soft, while still containing considerable concentrations of dissolved salts.
Well waters in low-lying areas near to the sea often of this type, owing to ingress of seawater through porous rock. Waters containing a preponderance of sodium bicarbonate are also not uncommon in some countries.
Equally, a water containing low total solids consisting largely of calcium salts, which is soft by ordinary standards, will be hard from the point view of ion exchange reactions, since the cation resin on exhaustion will be almost fully loaded with calcium.
The concept of hardness should always be perceived as separate from that of total mineral content. The term ‘hard’ and ‘soft’ is used to indicate the presence or absence of calcium and magnesium ions.
Where a broad indication of total dissolved solids is required, the convenient expressions ‘thin’ and ‘thick’ waters are used to indicate values of less than 100 ppm, and greater than 300 ppm, respectively.