By the end of 2017, toilet water and other wastewater will be used to irrigate a large swath of Central Valley farmland near Interstate 5, an area that is known as California’s agricultural hub because it produces more than 360 products. “As long as we keep taking showers and flushing toilets, we can guarantee you water,” Modesto Mayor Garrad Marsh said at a news event last August to farmers. Treatment facilities in the two inland cities, Modesto and Turlock, will collect the water from sinks, showers, washing machines and toilets, and process it into what’s commonly referred to as “gray water.”