Understanding TDS in Water: What is the Healthy Level?
Total Dissolved Solids (TDS) is the most common metric for water quality, but it is often misunderstood. Learn what TDS actually measures, the ideal range for drinking, and the myths surrounding it.
Walk into any home in India, and the first question about water is: "What is the TDS?" TDS (Total Dissolved Solids) has become the de-facto standard for judging water quality. But most people don't know what it actually represents.
Is 50 TDS good? Is 500 TDS bad? Let's decode the numbers.
What is TDS?
TDS stands for Total Dissolved Solids. It is a measure of the combined content of all inorganic and organic substances contained in a liquid in molecular, ionized, or micro-granular suspended form.
- Major constituents: Calcium, Magnesium, Sodium, Potassium (cations) and Carbonate, Bicarbonate, Chloride, Sulfate, Nitrate (anions).
- Measured in: Parts per million (ppm) or Milligrams per liter (mg/L).
Crucially: TDS tells you how much stuff is dissolved in the water, but not what that stuff is. It could be healthy calcium or toxic arsenic.
The Ideal Range Table
| TDS Level (mg/L) | Rating | Description |
|---|---|---|
| < 50 | Unacceptable | Tastes flat, corrosive, lacks minerals. Common in poorly tuned RO systems. |
| 50 – 150 | Acceptable | Generally safe, but may lack optimal mineral taste. |
| 150 – 300 | Excellent | The sweet spot. Good mineral balance, great taste, healthy. |
| 300 – 500 | Good | Acceptable by national standards. Slightly "heavy" taste possible. |
| 500 – 900 | Fair | Acceptable only if no other source is available. Can cause scaling. |
| 900 – 1200 | Poor | Salty taste. Not recommended for long-term drinking. |
| > 1200 | Unacceptable | Unsafe. High risk of kidney stones and other issues over time. |
The Problem with "Low TDS"
Many people believe "Zero TDS" is best. This is a myth. Drinking water with very low TDS (< 50 ppm) has consequences:
- Bitter/Flat Taste: Minerals give water its refreshing taste.
- Acidic pH: Low TDS water absorbs CO2 from the air and becomes acidic (pH 5.5 - 6.0), which is not ideal for the body.
- Mineral Leaching: Some studies suggest demineralized water can leech minerals from your body or cooking food.
- Corrosion: It is highly aggressive and corrodes copper plumbing.
The Problem with "High TDS"
High TDS (> 500 ppm) usually indicates hard water or saline intrusion.
- Bad Taste: Salty, metallic, or bitter.
- Scaling: Ruins pipes, heater elements, and RO membranes.
- Hidden Dangers: While high Calcium is fine, high TDS often hides high nitrates, fluorides, or arsenic, which are toxic.
Conclusion
Don't chase "Zero." Aim for a TDS of 150 to 300 ppm. If your source water is 2000 ppm, use an RO. If your source water is 200 ppm, you might not need an RO at all—simple filtration (UV+UF) might be better to preserve the natural minerals.
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