Water Softener Questions and
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 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 100p.p.m.
and greater than 300p.p.m., respectively. |
