TDS stands for Total Dissolved Solids. It is the total amount of dissolved inorganic salts and small amounts of organic matter present in water — mainly minerals such as calcium, magnesium, sodium, potassium, bicarbonates, chlorides, sulphates and nitrates. TDS is usually measured in milligrams per litre (mg/L) or parts per million (ppm). The TDS level affects the taste, quality and suitability of water for drinking. According to the Bureau of Indian Standards (BIS, IS 10500:2012), the acceptable limit of TDS in drinking water is 500 mg/L, and the maximum permissible limit (when no better source is available) is 2000 mg/L.
TDS stands for Total Dissolved Solids.
It is measured in mg/L (milligrams per litre) or ppm (parts per million).
BIS acceptable limit for drinking water is 500 mg/L; permissible limit is 2000 mg/L.
The 150–300 mg/L range is generally considered best for taste and health.
TDS is measured using a TDS meter (based on electrical conductivity).
TDS does not measure bacteria or viruses — low TDS does not mean germ-free water.
High TDS is reduced by Reverse Osmosis (RO), distillation or deionisation.
TDS (Total Dissolved Solids) is the combined content of all the dissolved substances in water. These include: • Minerals — calcium, magnesium, sodium, potassium • Salts — chlorides, sulphates, bicarbonates, nitrates • Small amounts of dissolved organic matter and metals
Note: TDS measures only the dissolved solids, not suspended particles, bacteria or viruses. So a low TDS does not mean the water is free of germs.
How it is measured: TDS is measured using a TDS meter, a small digital device that measures the electrical conductivity of water (dissolved salts conduct electricity). The reading is shown in mg/L or ppm. It can also be found in the laboratory by evaporating a known volume of water and weighing the residue left behind.
A commonly used guide for the suitability of drinking water by TDS level (in mg/L or ppm):
• Less than 50 — Too low; lacks essential minerals, not ideal • 50 to 150 — Acceptable; good if water is from a clean source • 150 to 300 — Good; generally considered the best range for taste and health • 300 to 500 — Fairly acceptable; within the BIS acceptable limit • 500 to 900 — Less acceptable; above the BIS acceptable limit, taste may be poor • 900 to 1200 — Poor; not recommended • Above 1200 — Unacceptable for drinking
BIS standard (IS 10500:2012): • Acceptable limit: 500 mg/L • Maximum permissible limit (in the absence of an alternate source): 2000 mg/L
Effects of high TDS:
Effects of very low TDS:
How to reduce high TDS:
Note: If the source water already has low TDS, an RO is usually not needed and may make the water too low in minerals.
According to the Bureau of Indian Standards (BIS, IS 10500:2012), the acceptable TDS limit for drinking water is 500 mg/L. The maximum permissible limit, when no better source of water is available, is 2000 mg/L. For best taste and health, a TDS of about 150–300 mg/L is generally considered ideal.
TDS stands for Total Dissolved Solids — the total amount of dissolved minerals and salts in water, such as calcium, magnesium, sodium, chlorides, sulphates and bicarbonates. It is measured in mg/L or ppm using a TDS meter. TDS affects the taste and quality of water but does not measure bacteria or viruses.
Very low TDS water (below about 50 mg/L) is not ideal because it lacks beneficial minerals like calcium and magnesium and may taste flat. A moderate TDS of around 150–300 mg/L is considered best, because it contains useful minerals while still tasting good. Extremely high TDS (above 1200 mg/L) is unacceptable for drinking.
High TDS is most commonly reduced by Reverse Osmosis (RO), which pushes water through a membrane that removes dissolved salts. Other methods are distillation (boiling and condensing the steam) and deionisation (using ion-exchange resins). If the source water already has low TDS, an RO is usually not necessary.
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