Before you buy a water purifier

Drinking untreated tap water is seen by many as akin to writing a suicide note—death by disease. Little wonder then that it has led to a booming bottled-water business.

Namrata Dadwal        Print Edition: September 4, 2008

Drinking untreated tap water is seen by many as akin to writing a suicide note—death by disease. Little wonder then that it has led to a booming bottled-water business. But as bottled water costs anything from Rs 35 to Rs 100 for 20 litres, it can blow a hole in any household budget. Which is where water purifiers come in—they promise clean, potable water for a fraction of the cost of the bottled stuff. It can, however, be a problem selecting a purifier, given the variety available in the market. To ease the dilemma, check out the filter that it is fitted with. The heart of a water purifier is its filter; if it’s not effective, you may as well throw the kit away. The filter you buy will depend on the purity of water supplied to your home. There are labs in almost every city that offer to test water quality (www.indiawaterportal.org has a comprehensive list of labs). Once you find this out, go through this beginner’s guide to water filters.

Once you know which filter you should choose, start checking out the brands. This is where word-of-mouth advertising pays off. So if you live in an apartment complex and a particular brand of water filter works well in your neighbour’s flat, you know which one to buy (or not). Also remember to find out about servicing, spares and cost of repair or replacement of filters. As a water filter is a long-term acquisition, there’s no point in buying one that you might have to throw away in a hurry. If all you want is use-and-throw, you may as well stick to bottled water.

How they compare

Type of filter

Contaminants removed

Price (Rs)Power requiredInstallation Cost (Rs)Replacement of filters
Bacteria & virusesSedimentsHeavy metalsTime periodCost (Rs)
Activated carbonNoYesPartly1,800-3,500NoNo3 months to 1 year150-200
UltravioletYesNoNo3,000-10,000YesYes6 months to 1 year; UV lamp will only need replacement if it is fused100-350 (filters) 500 (UV lamp)
Reverse osmosisPartlyYesYes9,000-25,000YesYes6 months to 1 year; 1-3 years for RO membrane100-350 (filters) Up to 2,500 (membrane)

Installation costs may vary

 

Activated carbon
The carbon granules in these filters are positively charged or impregnated with silver molecules.This means that they can remove pesticides and herbicides, chlorine, radon and other chemicals. The filters are rated by the size of particles—measured in microns— that they can remove. So a filter that measures 0.5 micron is more effective than the one that measures 10 microns.The best bit is that they are inexpensive and some are available in sizes small enough to be attached directly to the tap. Besides, they don’t need power to operate, so you save on the electricity bill too.
The flip side: These filters are ineffective against bacteria, viruses and heavy metals.

Ultraviolet
These filters use UV radiation to deactivate water-borne, disease-causing organisms.The unit uses the same amount of energy as a 60-Watt light bulb.
The flip side: These are unable to remove heavy metals or chemicals like arsenic, nirates and iron.

Reverse osmosis
The reverse osmosis or RO system is relatively new and uses a semi-permeable membrane to filter water.This membrane measures barely .0005 micron, and hence, can remove the minutest of impurities. It also desalinises water.
The flip side: These are not as effective as UV filters against bacteria and viruses.

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