Don’t buy this · Water
Don't buy a purifier on a TDS reading
The verdict
A TDS meter measures how easily electricity crosses your water. It cannot distinguish calcium from arsenic, it reads identically whether or not your water carries bacteria, and at the concentrations that matter for lead, arsenic and fluoride it does not move at all. A demonstration showing you a high number has demonstrated conductivity, not contamination — and it is the single most effective sales technique in Indian water treatment precisely because the number looks like evidence.
When this does not apply to you
Placed here rather than at the end, because if one of these describes your situation then the rest of this page is the wrong advice and you should know that now.
Your TDS is genuinely high — above about 500 ppm
Then RO is very likely the right technology, and the meter did its one useful job. High TDS is a real palatability problem and a real reason to buy. The argument here is against buying on the number alone, not against the number.
Your water tastes salty or bitter
Taste plus a high TDS reading is a coherent picture, and chloride or magnesium sulphate is a genuine reason for RO. Get chloride measured to confirm, then buy.
You are on an unfamiliar borewell
A TDS reading is a reasonable first screening step on unknown groundwater. It just cannot be the last one — the parameters that matter most on groundwater are the ones it cannot see.
Why you were told otherwise
Usually not because anyone lied to you. Almost every claim in this category is technically true and incomplete, which is a much more durable technique.
- A TDS meter is cheap, portable, and produces a large frightening number in ten seconds. Nothing else in water treatment demonstrates that well.
- The number is real. That is what makes the demonstration effective — nobody is faking the reading, they are simply letting you assume it means something it does not.
- RO is the highest-margin product in the category, and TDS is the only common measurement that RO obviously improves.
- Nobody selling a purifier benefits from you learning that a laboratory test costs ₹1,200 and would answer the question properly.
What to do instead
A page that only says no is an opinion. This is the part that makes it useful.
- 1
Measure your own TDS, then stop and think about it
Buy a ₹300 meter and read your own water at your own tap. Below 200 ppm, RO is probably the wrong purchase. Between 200 and 500, it depends on taste and on what else is in it. Above 500, RO is likely justified.
Read more → - 2
Get a laboratory panel before spending five figures
TDS, hardness, pH, chloride, nitrate, fluoride, iron and coliforms is roughly ₹1,200 to ₹3,000, and it answers the questions the meter cannot. Against a ₹15,000 purchase plus years of consumables, it is the cheapest decision in the process.
Read more → - 3
Run the Purifier Doctor first
Eight questions and you get a water profile, the specific tests worth paying for, and a technology recommendation that can legitimately come out as 'you do not need this'.
Read more →
Note
Frequently asked questions
Is high TDS water harmful?
Should I buy RO if my TDS is 150?
Why does the salesman's meter show a different number from mine?
Cost figures are indicative Indian market ranges for budgeting, last reviewed 2026-08-08. This page argues about the general case; the exceptions section above is where the specific case is dealt with, and it is written honestly rather than as a hedge.