Hi Chandan not to worry about that you should prefer Pureit water purifier,actually most of the my friend using it and they tell me that it is one of the best purifier.You can try it without any hesitation.
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Total Dissolved Solids or TDS calue in ppm in water decides the potability of water for drinking purposes. Lesser the value, better the quality. I would recommend to go for RO where in you can easily get this adjusted to about 45 or 50 to maintain taste and filtration quality.