Water quality for ZIP code 91901
ZIP 91901 covers Alpine, Harbison Canyon, and Descanso in San Diego County, California, one of 115 ZIP codes in the county. 198 active public water systems serve the county; 83 had an EPA violation in the past three years.
Most likely your provider
Other community water systems in San Diego County
81 systems, nearest firstNon-community systems in San Diego County (116: schools, campgrounds, workplaces, restaurants)
These systems serve places you visit rather than homes.
About this data
Water systems are matched to San Diego County, the county this ZIP code lies in, nearest to the ZIP code's centre first. Your exact provider depends on your address and connection; the largest community water system in a county is usually the city or town utility. Distances are measured to the centre of the service area EPA publishes for the system.
ZIP code areas and town boundaries come from the U.S. Census Bureau's 2020 ZCTA files.
Source: the U.S. EPA's Enforcement and Compliance History Online system (ECHO), which publishes the federal Safe Drinking Water Information System. EPA's terms and values are shown as published. The California records are from EPA's data refresh of Oct 7, 2026; EPA refreshes this data quarterly, and states report to EPA with a lag of three to six months, so the newest violations may not appear yet.