RO vs UV vs UF: Which Water Purifier Do You Actually Need?

RO removes what is dissolved in water. UV kills what is alive in water. UF filters out what is floating in water. They solve three different problems, which is why the right answer depends entirely on which problem you actually have.

Almost every purifier sold in India bundles two or three of these together, and salespeople tend to present more stages as unambiguously better. It is not that simple — buying RO for genuinely soft, treated municipal water wastes money, wastes two to three litres of water per litre purified, and strips out calcium and magnesium you would rather keep.

• Step 1 — Measure your TDS with a digital meter (~₹300). Do it in both summer and monsoon if your supply changes seasonally.
• Step 2 — Check whether your area has a documented arsenic, fluoride or nitrate issue. If yes, buy RO regardless of what the TDS says. These contaminants are invisible, tasteless, and can be present at normal TDS.
• Step 3 — TDS below 200 ppm and no contaminant concern → buy UV+UF. You will spend less, waste no water and keep your minerals.
• Step 4 — TDS 200-300 ppm → either works. UV+UF is the more economical and environmentally sensible choice.
• Step 5 — TDS above 300 ppm → buy RO with UV behind it, and insist on a TDS controller.
• Step 6 — Borewell, tanker or unknown source → buy RO+UV and design for the worst reading you have measured, not the average.

Stage counts are the most inflated number in this industry. Brands routinely count a sediment pad, a post-carbon polisher and a mineral cartridge as three separate 'purification stages' to reach a headline figure of 9, 10 or 12.

Ignore the count entirely. Read the specification and confirm which of these are genuinely present: an RO membrane, a UV lamp, a UF membrane, and a TDS controller. A well-built 6-stage purifier from a brand that services your city will outperform a 12-stage unit from one that does not.