They have become an essential part of every household and the quality of water they dispense taken as safe. But how good are the water filters with fake service companies mushrooming and tending the machines that are old?

Shelling out an extra buck on water purifiers may be a better choice than risk health but without any set manufacturing standards experts are questioning the effectiveness and authenticity of these purifying machines.

Manufacturers say that the business is flourishing at an unprecedented rate but there is no set parameter to check the water quality.

"Unfortunately we don't have any set standard on the part of government to check the authenticity of water purifiers or Reverse Osmosis (RO) systems. Reforms are required to fill-up the loop-holes, if there any," says Mahesh Gupta, Chairman, Kent RO, adding that the 1000 crore water purifier industry is growing at the rate of 20-25 per cent per year. "There is no denying a rising demand for purifiers in the last few years. My company profits grew 40 times between 2002 to 2007, from Rs 2.5 crore to 100 crore. We almost hold 40 per cent market share in RO business," he adds.

A 2005 study by US based consultancy firm Frost and Sullivan reveals that one in every 40 Indian households uses water purifiers. Eureka Forbes, Kent RO, Usha Brita and Ion Exchange are the big operators in the India purifier market.

Tarun Gupta, Director, Inside India Trade, an Indian consulting company, says that the quality of ground water in India has deteriorated over the years due to overexploitation leading to increase in demand of water purifiers and filters.