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Total Dissolved Solids in Your Swimming Pool
One of the measurements that can be taken on swimming
pool water is the Total Dissolved Solids level, or TDS. TDS is a measurement of
virtually everything dissolved in the water that is not H2O. This
includes such components as salts, minerals (like calcium and magnesium),
sulfates, silicates, organic and inorganic materials, tanning lotions and oils,
sweat, saliva, urine, soap, deodorant, hair spray, colognes and perfumes, plant
pollens, pet wastes, spilled food and softdrinks, dirt, lawn and garden
fertilizers, etc. Wow! There is quite a lot of dissolved material in that water
that is still clear to the human eye!
As water evaporates from the pool, the TDS increases because the sun
only removes distilled (pure) water and leaves all of the dissolved solids
behind (like when you leave a glass of water outside to evaporate... the white
crust left behind was "dissolved solids"). The "fresh" water
you then use to replace the evaporated pure water also contains its share of
dissolved solids. Normal evaporation rates are usually up to 1/4" per day
in the winter and 112" per day in the summer. Therefore the water in the
pool is continually getting "harder", or higher in dissolved solid
content.
High TDS can be a problem because they interfere with pH, hamper
chlorine's ability to affect bacteria and algae, create hazy water, contribute
to the corrosion of metal piping systems, and promote scale deposition on the
plaster and tile.
In swimming pool applications, TDS is normally measured by means of a
meter that passes electrical current through the water. Since most anything that
is not pure water conducts electricity, and since pure distilled water does not,
the amount of electricity that passes through can be read as a level of TDS.
Tap water TDS can range from 300 to 700 parts per million TDS. The
average in swimming pools is usually 1000 to 2000 ppm. The National Spa and Pool
Institute (NSPD recommends an upper limit of 3000 ppm).
TDS can be lowered through full or partial draining and refilling,
through the use of chelating agents, or through special nanofiltration. If you
wish to know the TDS level in your pool water, or if you are interested in
chelation or nanofiltration, please call us. |
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