Most important factor here is ASS
must be available doorstep.
Best way to find about status of doorstep ASS
is monthly meeting of housing society else talk with neighbours .
Also the ASS
shop must be on your daily route because my experience is that promises done by purifier cos. are often not kept. This
To know whether you really require RO or only UV (ultra violet ray) filter is enough , you need to measure the hardness and TDS (Total Dissolved Salts) of water which is provided for drinking by the civic authorities . Contact a RO purifier provider and ask him to measure it.
Some times the water provided by civic authority is already soft (eg Pune municipal corporation) , so only UV purifiers are enough. And they are cheaper than RO.
Drinking too much hard water can lead to kidney stones hence RO is must. In such situations it is better to purchase RO + UV purifier Because if RO filter fails UV provides back up. When RO filter is working, it removes micro organisms from water and also removes harmful and extra minerals while maintaining correct and optimum quantity of minerals in the output water , hence UV is not required because UV works by killing microorganisms also UV doesn't manage minerals at all.
RO demands high maintenance if the water to be purified is muddy (I mean it contains fine earth particles)or if water is too hard (more than 300mg/lit) or TDS (i.e. Total Dissolved Salts ) is more than 500.
If levels are bellow the figures mentioned, maintenance is low. i. e. Rs 350 to 450 for one filter, you have to replace 3 such filters at a time every 6000 lits. The RO membrane requires replacement every 12000 lits of purified water. Cost of RO membrane which is used when TDS contents of water to be purified is less than 500 mg/lit is Rs 2200 approx.
So key step is to measure hardness and TDS content of the water supplied by civic authority.
Broadly, TDS content of well and bore well water is above 500 to 800.This requires higher rated costly RO filters, while water from lakes, rivers have TDS levels of 200 to 500, this often reduces to 100 after the filtration process followed by civic authorities.
Second important factor is pressure of the input water. If it is low then there are few purifiers which comes with in built motor to improve pressure and they are electricity dependent. So electric supply scenario of your area decides their true utility.
While few work only on high pressure of input water and do not require electricity.
It is important to go through website of purifier Co s. such as Eureka forbes, ion exchange(zero B), Kent, Nasaka etc. They have variety of purifiers with various utility and comfort features . You can choose as per your requirements. For eg. Radium indicators for water level., Hidden purifier under kitchen table and tap available at sink . wall mountable, table top mountable etc.