TDS Level in Drinking Water: What Is Safe? (India Guide)

Your TDS meter just beeped 780 ppm. Is that dangerous? Should you panic? Or is 150 ppm actually too low? TDS (Total Dissolved Solids) is one of the most misunderstood water quality parameters — and marketers have made the confusion worse. Here is what the science and Indian standards actually say.

What Is TDS?

Total Dissolved Solids (TDS) is a measurement of all inorganic and organic substances dissolved in water, expressed in parts per million (ppm) or milligrams per litre (mg/L). These dissolved substances include:

Minerals: calcium, magnesium, potassium, sodium (generally beneficial)
Heavy metals: lead, arsenic, mercury, chromium (harmful at elevated levels)
Salts: chlorides, sulfates, nitrates (harmful in excess)
Industrial contaminants: pesticides, solvents (harmful)

Here is the crucial insight: TDS tells you HOW MUCH is dissolved, but not WHAT is dissolved. A high TDS reading could mean mineral-rich spring water (mostly harmless) or heavily contaminated industrial water (dangerous). Context is everything.

TDS Standards for Drinking Water in India

Standard Body	Maximum Acceptable	Desirable Limit	Status
BIS (IS 10500:2012)	500 ppm	300 ppm	Indian national standard
WHO	600 ppm (guideline)	300 ppm (recommended)	International guideline
USEPA	500 ppm	No specific guideline	US standard
EU Drinking Water Directive	No mandatory limit	Below 500 ppm recommended	EU guideline

TDS Level Categories: What Each Range Means

TDS Range (ppm)	Category	Taste Profile	Health Impact	Action Needed
0–50	Extremely Low	Flat, bland	Mineral deficiency risk with long-term use	Add mineraliser; use only with RO + mineraliser
50–150	Excellent	Clean, fresh	Optimal for health	Ideal purified water range
150–300	Good	Slightly mineral	No concerns; beneficial minerals present	Good range; no action needed
300–500	Acceptable	Noticeable taste	Generally safe; monitor specific contaminants	Consider RO if borewell or industrial area
500–900	Poor	Salty/bitter notes	May cause scale deposits; monitor for metals	RO purification strongly recommended
900–1200	Very Poor	Distinctly unpleasant	Health risks with prolonged exposure	Do not drink without RO purification
Above 1200	Dangerous	Undrinkable	Serious health risks; likely toxic contaminants	Immediate water treatment or alternative source

How to Measure TDS at Home

A TDS meter is a small digital device that measures electrical conductivity of water (dissolved ions conduct electricity), then converts this to a TDS reading. They are available online for Rs 200–800.

How to Use a TDS Meter

Remove cap and turn meter on
Dip the probe end 2–3 cm into the water sample
Gently stir for 10 seconds to stabilise reading
Read the display (most show ppm directly)
Multiply by temperature compensation factor if needed (press TEMP button)
Rinse probe with distilled water after use

Pro Tip: Test Multiple Points

Test directly from source tap (before purifier)

Test from purifier output to check if your RO is working

Test from storage tank to monitor water quality over time

A good RO should reduce TDS by 85-95% — if not, membrane may need replacement

TDS by City: What to Expect Across India

City / Region	Typical Source TDS	Common Issues
Delhi NCR	300–600 ppm (municipal), 800–1500 (borewell)	Arsenic traces, high hardness
Mumbai	100–250 ppm	Bacterial, chlorine; relatively low TDS
Bangalore	150–350 ppm	Moderate; varies by area
Chennai	400–800 ppm	High TDS from coastal aquifers, hardness
Kolkata	200–400 ppm	Arsenic risk in East zone, bacterial
Rajasthan (rural)	800–2000+ ppm	Fluoride contamination, extremely high TDS
Punjab (rural)	300–800 ppm	Nitrates from agriculture, arsenic risk
Coastal Karnataka	250–600 ppm	Saline intrusion near coast

The Zero TDS Myth

Many salespeople and some brands promote ‘zero TDS purified water’ as the healthiest option. This is misleading. WHO and research scientists have noted that long-term consumption of demineralised water may:

Increase risk of magnesium and calcium deficiency
Lead to higher uptake of heavy metals (demineralised water is more aggressive in leaching)
Cause electrolyte imbalance in some populations

The ideal output TDS from a home RO purifier is 75–150 ppm, achieved via a TDS controller or mineraliser cartridge. This retains essential minerals while removing harmful dissolved solids.

Frequently Asked Questions (FAQ)

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What is the ideal TDS for drinking water in India?

The BIS standard (IS 10500:2012) recommends a desirable TDS limit of 300 ppm with an acceptable maximum of 500 ppm. Most water quality experts and the WHO suggest 100–300 ppm as the optimal range for daily drinking water. After RO purification, an output of 75–150 ppm with mineraliser is ideal.

Is 400 ppm TDS water safe to drink?

400 ppm TDS is within the BIS acceptable limit of 500 ppm and is generally safe for drinking. However, the safety depends on what is contributing to that TDS. If it is calcium and magnesium (natural hardness), it is safer than if fluoride, arsenic, or industrial chemicals are present. Always verify the source before drinking.

My RO output TDS is 20 ppm. Is that too low?

Yes, 20 ppm is very low and indicates that your RO is removing nearly all minerals. This is technically ‘over-purified’ water. Long-term consumption without a mineraliser may lead to mineral intake reduction. Ensure your purifier has a functional mineraliser cartridge and replace it as per the maintenance schedule (usually every 6–12 months).

Can I drink water with TDS of 1000 ppm?

No. Water with TDS above 600–700 ppm has a noticeably unpleasant taste and may pose health risks depending on what contributes to the high TDS. At 1000 ppm, you should not consume this water regularly without proper RO purification. Use an RO purifier that can reduce it to below 150 ppm.