How to Read a Water Test Report: What Each Line Actually Means
You paid for a water test and got back a page of parameters and numbers. Most people look at the TDS line, shrug, and file the report away. The report is actually readable once you know what the two columns beside each parameter mean. This guide walks through it line by line, using the limits in the Indian drinking water standard, BIS IS 10500:2012.
The two limits every Indian report uses
Most Indian labs report against BIS IS 10500:2012, and for many parameters the standard gives two figures. The first is the acceptable limit. The second is the permissible limit in the absence of an alternate source. Aim for the acceptable limit. The permissible limit is a fallback for places with no better water available, never a target. Some parameters carry no relaxation at all, so the acceptable limit is the only limit.
The physical lines: colour, odour, turbidity
Turbidity is cloudiness from suspended particles such as silt and clay. BIS IS 10500:2012 sets an acceptable limit of 1 NTU and a permissible limit of 5 NTU. The same particles also shield germs from disinfection, so cloudy water is harder to make safe.
pH
BIS IS 10500:2012 asks for a pH between 6.5 and 8.5, with no relaxation. Below 6.5 the water is acidic and corrosive, and it slowly eats pipes, taps and geyser elements. Above 8.5 usually points to high mineral content rather than a health problem in itself. Our guide to common water impurities covers what those minerals are.
TDS and hardness: the two everyone talks about
Total dissolved solids is the total dissolved load in the water, from salts to minerals. Hardness is mainly the calcium and magnesium within that load, the part that scales kettles and marks taps. Alkalinity is the water’s ability to resist changes in pH. BIS IS 10500:2012 gives TDS an acceptable limit of 500 mg/L and a permissible limit of 2000 mg/L. Total hardness and total alkalinity, both measured as CaCO3, each have an acceptable limit of 200 mg/L and a permissible limit of 600 mg/L. See our guides on the best TDS level for drinking water, the health effects of high TDS and hard water problems.
The salty lines: chloride and sulphate
These are the lines behind a salty or bitter taste. BIS IS 10500:2012 gives chloride an acceptable limit of 250 mg/L and a permissible limit of 1000 mg/L. Sulphate has an acceptable limit of 200 mg/L and a permissible limit of 400 mg/L. Both also corrode metal fittings.
The health lines you must not ignore
Two lines matter most, because the water can look and taste fine while they are out of range. For fluoride, BIS IS 10500:2012 sets an acceptable limit of 1.0 mg/L and a permissible limit of 1.5 mg/L. Long-term excess fluoride affects teeth and bones. Nitrate is limited to 45 mg/L with no relaxation, and excess nitrate is a specific risk for infants. If either line is over, the water needs treatment even when nothing about it seems wrong. Both are common in borewell water, and neither can be seen, smelt or tasted.
The staining lines: iron and manganese
BIS IS 10500:2012 gives iron an acceptable limit of 0.3 mg/L. Manganese has an acceptable limit of 0.1 mg/L and a permissible limit of 0.3 mg/L. Iron gives a reddish-brown stain and a metallic taste, manganese a darker, blackish one. Our guide to iron in water explains why the stain appears after the water has stood.
The bacteriological lines
Total coliform and E. coli tell you whether the water carries germs from sewage or animal waste. Under BIS IS 10500:2012 they shall not be detectable in any 100 ml sample, with no relaxation. This is the one line where “slightly over” does not exist. Any detection means act immediately: boil or otherwise disinfect until the source is fixed. Where the supply is chlorinated, the report may also show residual free chlorine. BIS IS 10500:2012 asks for a minimum of 0.2 mg/L at the consumer end, the sign that disinfection is still working at your tap.
Common report lines at a glance
All figures below are from BIS IS 10500:2012.
| Line | Acceptable limit | Permissible limit | What it means for you |
|---|---|---|---|
| pH | 6.5 to 8.5 | no relaxation | Low corrodes pipes; high means mineral-rich water |
| Turbidity | 1 NTU | 5 NTU | Cloudy water that shields germs |
| TDS | 500 mg/L | 2000 mg/L | Total dissolved load; taste and scale |
| Total hardness (as CaCO3) | 200 mg/L | 600 mg/L | Scale on kettles and geysers |
| Chloride | 250 mg/L | 1000 mg/L | Salty taste, corroded fittings |
| Sulphate | 200 mg/L | 400 mg/L | Bitter taste, corroded fittings |
| Fluoride | 1.0 mg/L | 1.5 mg/L | Invisible; affects teeth and bones |
| Nitrate | 45 mg/L | no relaxation | Invisible; risk for infants |
| Iron | 0.3 mg/L | no figure stated here | Brown stains, metallic taste |
| Manganese | 0.1 mg/L | 0.3 mg/L | Black stains |
| Total coliform / E. coli | not detectable in any 100 ml | no relaxation | Any detection: disinfect now |
Three mistakes people make reading a report
- Treating the permissible column as the goal. It exists for places with no alternative source. Between the two columns, you have a treatment job, not a pass.
- Testing at the source instead of the tap. A sample from the borewell mouth says nothing about what the tank, the old pipes and the geyser add on the way. Test the tap people actually drink from.
- Testing once. Borewell chemistry shifts across the seasons as the water table rises and falls. One report is a snapshot, not a permanent description.
What to do with your report
Each line points to a kind of treatment, so match them up. High TDS, hardness, fluoride or nitrate means filtration that removes dissolved substances. Coliform means disinfection. Iron or manganese means treatment for staining and taste. Low pH means corrosion in the plumbing, which no purifier fixes. Then pick the purifier for what your report actually shows, not for what a salesperson says. Our RO vs UV vs UF buying guide explains which technology handles which line.
If the report shows dissolved salts alongside a germ risk, a combined unit covers both. The LUXGEN Royale Copper runs water through RO, UV and UF in sequence, adds a copper cartridge after purification, and has a TDS controller that can be tuned to your supply.
One more thing
Packaged drinking water is covered by a separate standard, IS 14543, not IS 10500. The numbers on a bottle label and the columns on your report are therefore not directly comparable.
Bottom line
A water test report is not a pass or fail stamp. It is a list of instructions. Once you can read the two columns, it tells you exactly what to treat and what you can safely leave alone. Keep the report, test again next season, and let the lines, not the sales pitch, decide what goes under your sink.
