what are Totally Dissolved Solids?
Totally Dissolved Solids (TDS)
is a term which describes the concentration of minerals and salts dissolved in the water. The unit of measurement is milligrams per litre (mg/L), which is equivalent to parts per million or ppm. The simplest method of measurement involves measuring the electrical conductivity of the sample using a meter which converts the conductivity reading to mg/L or ppm. Such meters are readily available from your local home brew shop.
The most common salts found in water contain calcium, magnesium, sodium and potassium in combination with carbonates, bicarbonates, sulphates, nitrates, phosphates and chlorides.
Seawater
Has a TDS of about 35,000 ppm, comprised mostly but not exclusively of sodium chloride (“common salt”). Many of the other salts in seawater are listed in Reference 2.
Borewater
Commonly has a TDS of more than 2000 ppm, often comprised of the carbonates, bicarbonates and sulphates of calcium and magnesium
Brackish water
Has a TDS between about 3000 and 10,000 ppm
“Fresh” water
Has a TDS defined variously as less than 500ppm or less than1000 pp
Rainwater
When collected under ideal conditions has a TDS between about 5 and 40 ppm
Distilled water
Has a TDS from 1 to 4 ppm
The taste of water with a TDS above 1500 ppm is generally unacceptable to the human palate. Cattle will drink water with a TDS less than 2000 ppm, however sheep and kangaroos are less discerning and will accept water with a TDS up to about 3000 ppm.
