Half of India over-pays for RO water that doesn't need it; the other half drinks under-purified borewell water. The decision takes one measurement — your water's TDS — and this guide.
Step 1: measure your TDS
A digital TDS meter costs ₹200-400. Test your drinking water source. Above 500 ppm: RO is necessary (only RO removes dissolved solids). 200-500 ppm: RO+UV or RO with TDS controller. Below 200 ppm (typical municipal supply): UV+UF or gravity purifiers are enough — RO would strip beneficial minerals unnecessarily.
What each technology does
RO forces water through a membrane, removing dissolved salts, heavy metals, and microbes — the only tech that lowers TDS. UV kills bacteria and viruses with light but leaves dissolved solids untouched. Gravity/UF filters physically strain dirt, cysts, and some bacteria — zero electricity, fine for already-clean municipal water.
The mineral question
Good RO purifiers include TDS controllers or mineralisers that retain/re-add essential minerals (calcium, magnesium). If you buy RO, buy one with this — plain RO water over years is mineral-light.
| Your water | TDS | Right purifier | Examples |
|---|---|---|---|
| Borewell/tanker, hard | 500+ ppm | RO+UV+UF with TDS control | Kent Grand+, AO Smith Z9 |
| Mixed/municipal mix | 200-500 ppm | RO+UV or UV+MTDS | Aquaguard Marvel, Livpure Glo |
| Clean municipal supply | <200 ppm | UV+UF or gravity | Pureit UV, Tata Swach gravity |
The verdict
Test first, buy second. High TDS: Kent Grand+ or AO Smith Z9 — RO with mineral control is non-negotiable. Municipal supply under 200 TDS: you'll get equally safe water from a UV purifier or gravity filter at a third of the cost and near-zero running expense.
Our picks
Full RO+UV+UF stack with TDS control
RO+UV+MTDS with copper enrichment
No electricity, near-zero running cost
FAQs
Is RO water bad for health?
Basic RO strips minerals — but every recommended RO here includes TDS control or mineralisers that retain calcium and magnesium. The 'RO is unhealthy' claim applies to bare-bones ROs only.
How often do I change filters?
Pre-carbon and sediment: ~6 months. RO membrane: 12-24 months. UV lamp: yearly. Budget ₹2,000-4,000 annually for an RO; gravity filters cost a fraction.