TDS meters and home water test kits: what they can and cannot tell you
Home kits are useful for quick checks between laboratory tests. But each kit measures only one thing, and none of them can tell you whether water is safe to drink. Here is what each kind of kit actually measures, and which ones we suggest.
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TDS meter: dissolved salts only
A TDS meter measures total dissolved solids (minerals and salts) in parts per million (ppm). IS 10500 sets an acceptable limit of 500 mg/l for drinking water, extendable to 2000 mg/l where no better source exists.
It is the best way to see whether you need an RO purifier at all, and to notice when RO filters are wearing out (the output TDS climbs).
What it cannot do: detect bacteria, arsenic, lead, nitrate, fluoride or pesticides. Water with a "good" TDS can still be unsafe.
Konvio Neer Digital TDS Meter
Quick check of total dissolved solids in tap, borewell, RO and packaged water. Handy for seeing when RO filters need changing.
Lab note: Measures dissolved salts only. It cannot detect bacteria, arsenic, lead or pesticides.
Check price on AmazonThemisto TDS-10 TDS Meter
Pocket TDS tester with a wide range, useful for comparing raw water, RO output and reject water.
Lab note: Calibrate as per the manual; readings drift if the probe is not rinsed.
Check price on AmazonpH meter or strips
Drinking water should be between pH 6.5 and 8.5. A digital pH meter gives a decimal reading but needs calibrating with buffer solution; strips are cheaper and give an approximate value.
Bionexis 5-in-1 Digital pH & TDS Meter
One device for pH and TDS: good for aquariums, hydroponics, RO output and alkaline-water checks.
Lab note: pH probes need regular calibration with buffer solution to stay accurate.
Check price on AmazonKonvio Neer pH Test Strips (1–14)
Low-cost dip-and-read pH check for drinking water, pool water and soil.
Lab note: Colour matching gives an approximate value, not a decimal reading.
Check price on AmazonHardness and chlorine kits
A hardness kit tells you how much calcium and magnesium is in the water, which is what causes white scale on taps, geysers and boilers. A chlorine kit checks residual chlorine in municipal supply or after tank cleaning.
BIONIX Total Hardness Test Kit
Find out how hard your water is: useful before buying a softener and for boiler or geyser scaling problems.
Lab note: Drop-count titration kit; follow the drop counts carefully.
Check price on AmazonChloroscope Chlorine Test Kit
Checks residual chlorine in municipal supply, overhead tanks after cleaning, and chlorinated well water.
Lab note: Colour comparison; test immediately after collecting the water.
Check price on AmazonCommon questions
Can a TDS meter tell me if water is safe to drink?
No. It measures dissolved salts only. Bacteria such as coliforms and E. coli, and chemicals such as arsenic, fluoride and lead, need a laboratory test.
What TDS is good for drinking water?
IS 10500 gives 500 mg/l as the acceptable limit. Very low TDS (below about 50) from an over-tuned RO is also not ideal for taste.
How often should drinking water be lab tested?
At least once a year for a home, after any flooding or pipe work, and every quarter or more often for housing societies, restaurants and institutions.
Need a definite answer?
Home kits and purifiers are no substitute for a laboratory report. We test drinking water to IS 10500 and food to FSSAI standards, with sample pickup across Kolkata.