Tapcensus

California

San Mateo County drinking water quality

51 active public water systems serve 776,653 people in San Mateo County. 36 are compliant, 15 had at least one EPA violation in the past three years, 0 are designated serious violators, and 3 carry a health flag.

Active systems 51 36 community systems
People served 777K by public water systems
Systems with violations 15 29% of active systems, past 3 years
Serious violators 0 3 systems carry a health flag

Needs attention

Pigeon Point Hostel CA4100553 · Transient non-community system · Serves 67 1 rule violated in the past three years. Unresolved: Surface Water Treatment Rule (SWTR).
Skylawn Memorial Park (skylawn Inc) CA4100605 · Non-Transient non-community system · Serves 50 1 rule violated in the past three years. Unresolved: Lead and Copper Rule Revisions (LCRR).
Puente Housing Solutions CA4100610 · Community water system · Serves 28 1 rule violated in the past three years. Unresolved: Surface Water Treatment Rule (SWTR).

Community water systems

36 systems, largest first
SystemServesStatusRules violated, 3 yrUnresolved
California Water Service San Mateo
 103,536 0 0
City of Daly City
Daly City 		102,593 0 0
City of Redwood City
Redwood City 		90,043 0 0
California Water Service-S San Francisco
 62,609 0 0
California Water Service Bear Gulch
 60,382 0 0
City of San Bruno
San Bruno 		42,631 0 0
North Coast County Water Dist
 38,546 0 0
Estero Municipal Improvement District
 36,556 0 0
California Water Service San Carlos
 34,801 0 0
City of Burlingame
Burlingame 		32,453 0 0
Mid-Peninsula Water District
 31,059 0 0
City of East Palo Alto
East Palo Alto 		29,519 0 0
City of Millbrae
Millbrae 		22,795 1 0
Menlo Park Municipal Water
Menlo Park 		22,362 0 0
Coastside County Water District
 19,033 0 0
Westborough Water District
 13,486 0 0
Town of Hillsborough
 11,766 0 0
Montara Water and Sanitary District
 6,088 0 0
City of Brisbane
Brisbane 		3,434 0 0
Palo Alto Park Mutual Water Company
 2,900 0 0
O'connor Tract Co-Operative Water Co.
 2,789 0 0
Guadalupe Valley Mid
 1,455 0 0
Cuesta la Honda Guild INC
 863 0 0
County Service Area 11
 450 0 0
County Service Area 7
 300 1 0
Butano Canyon Mutual
 150 0 0
Portola Improvement Association Mwc
 80 1 0
Bianchi Flowers INC
 65 1 0
Loma Mar Mutual
 65 0 0
Redwood Terrace Mutual
 56 1 0
Camp Jones Gulch
 44 0 0
Oku Incorporated
 35 3 2
Redwood Glen Camp & Conference Ctr
 31 0 0
Marchi Central Farm
 30 2 0
Puente Housing Solutions
 28 1 1
Camp Loma Mar
 25 2 0
Non-community systems (15: schools, campgrounds, workplaces, restaurants)

These systems serve places people visit rather than homes.

SystemServesStatusRules violated, 3 yrUnresolved
San Mateo County Memorial Park
 1,790 0 0
Csp Ano Nuevo State Park
 709 0 0
Optimists Volunteers for Youth
 205 1 0
Csp Portola State Park
 172 0 0
Butano Girl Scout Camp
 154 0 0
Butano State Park Csp
 121 0 0
Harley Farms Goat Dairy
 113 0 0
Pigeon Point Hostel
 67 1 1
Skylawn Memorial Park (skylawn Inc)
 50 1 1
Martins Beach Water System
 49 1 0
UC Elkus Ranch
 34 0 0
Costanoa Campground
 33 1 0
Gazos Creek Beach House
 33 0 0
LA Honda Center
 33 0 0
San Gregorio Company
 32 1 0
Inactive systems (62, no longer operating or reporting)

Kept for the record and excluded from the county totals above. Browse inactive systems.

About this data

Totals cover active systems. Systems serving more than one county are counted in each county. EPA counts the rules a system was in violation of, not the individual violations; one rule can carry several.

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. Retrieved from ECHO on Oct 11, 2026.