Reverse osmosis water purifiers waste almost 70-80% water during the purification process. RO are hugely popular and this has led to massive wastage of water. Most people are unaware of the fact that demineralisation of water is not required if the TDS in the input water is less than 500mg/litre. Because of this reason NGT has asked the centre to ban RO water purifiers in places were water supply has TDS lower than 500mg/ltr. However, this was challenged in the Supreme Court which had declined to intervene.