toilet to tap
n.— «Atwater plans to ramp up efforts to recycle wastewater for potable use, as Orange County has already done. (This process is sometimes disparagingly referred to as “toilet to tap.” In fact, it produces water so pure that, untreated, it corrodes metal pipes.)» —“Channeling Mulholland” Los Angeles Times Feb. 25, 20008. (source: Double-Tongued Dictionary)