Although most residents have safe drinking water, more than 250 water systems serving 900,000 people were out of compliance with drinking water standards in 2020. This is a chronic issue for some systems; more than 170 have been out of compliance for three or more years. More than half of these noncompliant systems are in the San Joaquin Valley—California’s largest farming region and home to a third of the state’s low-income communities. Some tribal water systems face similar challenges. Data are lacking on water quality provided by roughly 1,500 very small, county-regulated water systems and more than 350,000 domestic wells, but some of these supplies may have chronic issues as well.