text: Household RO units use a lot of water because they have low back pressure. Household RO water purifiers typically produce one liter of usable water and 3-25 liters of wastewater. The remainder is discharged, usually into the drain. Because wastewater carries the rejected contaminants, recovering this water is not practical for household systems. Wastewater is typically delivered to house drains. A RO unit delivering  of treated water per day also discharge between . This led India's National Green Tribunal to propose a ban on RO water purification systems in areas where the total dissolved solids (TDS) measure in water is less than 500 mg/liter. In Delhi, large-scale use of household RO devices has increased the total water demand of the already water-parched National Capital Territory of India.