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High TDS is the single most common reason an Indian household needs a purifier at all, and the single most common reason a purifier fails early. The rule is simple: your membrane's rated input TDS must exceed your actual supply TDS, with headroom for seasonal variation.
Most mainstream RO purifiers are rated to 2,000 ppm, which covers the large majority of Indian supply including most borewells. Above that — parts of Rajasthan, coastal Tamil Nadu and Gujarat, where 2,000-2,500 ppm occurs — you need a 3,000 ppm rated unit like the AO Smith Z9, or a domestic system with anti-scalant dosing ahead of the membrane.
Two things people get wrong. First, they buy a purifier rated exactly at their measured TDS, then find summer tanker water is 40% higher and the membrane dies in five months. Second, they skip the TDS controller — but on very high input TDS, output can still be higher than ideal, and the controller lets you manage the blend properly.
Measure before buying. A ₹300 TDS meter, tested in both summer and monsoon, will tell you more than any product page.
