IS 10500: Understanding the Indian Standard for Drinking Water
A complete breakdown of IS 10500:2012, the official drinking water specification in India. Learn the difference between 'Acceptable Limits' and 'Permissible Limits'.
In India, the Bureau of Indian Standards (BIS) sets the benchmark for safe drinking water under IS 10500:2012. This standard is crucial because it accounts for the diverse geographical conditions of the country, where many regions rely on groundwater that may not meet the strictest international norms.
The standard defines two distinct limits for many parameters:
- Acceptable Limit: The ideal value. If water exceeds this, it is technically "impure."
- Permissible Limit (in absence of alternate source): The absolute maximum allowed if no better water source is available. This allows for survival in water-stressed regions.
Key Parameters & Limits (IS 10500:2012)
Organoleptic and Physical Parameters
| Parameter | Acceptable Limit | Permissible Limit |
|---|---|---|
| Color (Hazen) | 5 | 15 |
| Odor | Agreeable | Agreeable |
| pH | 6.5 – 8.5 | No Relaxation |
| Turbidity (NTU) | 1 | 5 |
| TDS (Total Dissolved Solids) | 500 mg/L | 2000 mg/L |
General Chemical Parameters
| Parameter | Acceptable Limit | Permissible Limit |
|---|---|---|
| Calcium (Ca) | 75 mg/L | 200 mg/L |
| Magnesium (Mg) | 30 mg/L | 100 mg/L |
| Total Hardness (as CaCO3) | 200 mg/L | 600 mg/L |
| Alkalinity | 200 mg/L | 600 mg/L |
| Chloride | 250 mg/L | 1000 mg/L |
| Sulphate | 200 mg/L | 400 mg/L |
| Iron | 0.3 mg/L | No Relaxation |
| Fluoride | 1.0 mg/L | 1.5 mg/L |
Toxic Substances: The Non-Negotiables
For toxic heavy metals, the standards are much stricter. There is often no relaxation because these substances can cause immediate or chronic health issues even in tiny amounts.
| Substance | Limit (mg/L) | Health Impact |
|---|---|---|
| Arsenic | 0.01 / 0.05* | Cancer, skin lesions. |
| Lead | 0.01 | Brain damage, specially in children. |
| Mercury | 0.001 | Nervous system damage. |
| Chromium | 0.05 | Liver and kidney issues. |
| Cyanide | 0.05 | Immediate toxic effect. |
| Pesticides | Absent | Endocrine disruption. |
*The permissible limit (0.05) applies only where no alternate source is available.
Global Comparison: IS 10500 vs. WHO vs. US EPA
| Parameter | IS 10500 (Acceptable) | WHO Guidelines | US EPA (MCL) |
|---|---|---|---|
| TDS (mg/L) | 500 | ~600 (not mandatory) | 500 (Secondary) |
| Fluoride (mg/L) | 1.0 | 1.5 | 4.0 |
| Lead (mg/L) | 0.01 | 0.01 | Zero (Goal) |
| Iron (mg/L) | 0.3 | No Guideline | 0.3 |
Observation: You'll notice that India's "Permissible Limit" for Fluoride (1.5) is exactly the WHO's recommendation. India is more cautious with the "Acceptable" limit (1.0) because of the prevalence of skeletal fluorosis in many states.
Action Plan: What if your water fails?
If a laboratory report shows your water exceeds the limits, don't panic. There is a solution for every parameter:
| Failed Parameter | Likely Cause | Treatment Required |
|---|---|---|
| High TDS / Chloride | Brackish groundwater | Reverse Osmosis (RO) |
| High Hardness | Calcium/Magnesium rocks | Water Softener |
| High Iron / Manganese | Rusting pipes/Ores | Iron Removal Filter |
| Bacteria / E.coli | Sewage contamination | UV Sterilization / Chlorine |
| Turbidity (Cloudy) | Silt / Mud | Sand Filter / PSF |
| High Fluoride | Natural volcanic ores | Activated Alumina / RO |
When to Test your Water?
A one-time test is not enough. Groundwater quality changes with the seasons.
- Pre-Monsoon (June): Minerals are at their most concentrated (high TDS).
- Post-Monsoon (October): Risk of bacterial contamination is highest due to rainwater seepage.
- Recommended Frequency: At least once every 12 months for chemical parameters, and every 6 months for biological parameters.
Bacteriological Quality
Just like WHO guidelines, IS 10500 mandates:
- E. coli: Shall not be detectable in any 100 ml sample.
- Total Coliform: Shall not be detectable in any 100 ml sample.
Why the "Permissible Limit" Matters
In many parts of India, groundwater TDS naturally exceeds 500 ppm, or Hardness exceeds 200 ppm. The BIS acknowledges that drinking water with 1500 ppm TDS or 500 ppm Hardness, while not ideal, is generally safe for short-to-medium term consumption and is better than having no water.
However, for modern homes with access to purification technology (RO), we should always aim for the Acceptable Limit.
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