County · California
San Luis Obispo County, California: drinking water records
This overview covers 23 ZIP codes and 74 community water systems in San Luis Obispo County. It also stands in for 4 ZIP codes whose utility has too little EPA data for a page of its own.
System population figures are summed from EPA registry records and can overlap where wholesalers and retail systems serve the same people. They are not a Census county-population estimate.
Water systems with the most complete records
| Water system | People served | PFAS survey results | PFAS found | Health-based violations | Lead, 9 in 10 homes at or below |
|---|---|---|---|---|---|
| Pismo Beach Water Department CA4010008 | 8,036 | 240 | 0 | 3 | 0 ppb |
| Cambria Comm Services Dist CA4010014 | 5,532 | 120 | 0 | 2 | 0 ppb |
| Heritage Ranch CSD CA4010012 | 2,956 | 120 | 0 | 15 | 0 ppb |
| San Luis Obispo Water Department CA4010009 | 47,788 | 120 | 0 | 0 | 0 ppb |
| City of Paso Robles Water Division CA4010007 | 31,176 | 780 | 7 | 0 | 0 ppb |
| Atascadero Mutual Water Co CA4010002 | 30,618 | 240 | 5 | 0 | 0 ppb |
| City of Arroyo Grande Utilities Division CA4010001 | 17,963 | 240 | 6 | 0 | 0 ppb |
| California Mens Colony CA4010830 | 15,000 | 125 | 0 | 0 | 0 ppb |
| Nipomo Comm Services Dist CA4010026 | 13,771 | 360 | 0 | 0 | 0 ppb |
| Morro Bay Pw Dept - Water Division CA4010011 | 13,757 | 120 | 0 | 0 | 0 ppb |
| City of Grover Beach Public Works Dept CA4010004 | 12,701 | 180 | 0 | 0 | 0 ppb |
| Templeton CSD CA4010019 | 8,011 | 270 | 2 | 0 | 0 ppb |
| Oceano Comm Services Dist. CA4010005 | 7,601 | 240 | 0 | 0 | 0 ppb |
| Los Osos Community Services District CA4010016 | 7,086 | 420 | 8 | 0 | 0 ppb |
| Golden State Water Company - Los Osos CA4010017 | 5,924 | 240 | 4 | 0 | 0 ppb |
| Golden State Water Company - Nipomo CA4010018 | 4,506 | 180 | 1 | 0 | 5.2 ppb |
| Atascadero State Hospital CA4010832 | 4,100 | 60 | 5 | 0 | 0 ppb |
| Nacimiento Water Company CA4010027 | 2,181 | 0 | 0 | 21 | 0 ppb |
| San Miguelito Mwc CA4010003 | 1,600 | 0 | 0 | 2 | 0 ppb |
| Lopez Project CA4010022 | 1,569 | 0 | 0 | 1 | 0.8 ppb |
| Woodland Park Mutual Water Co CA4000506 | 538 | 0 | 0 | 12 | 12 ppb |
| San Simeon CSD CA4000568 | 462 | 0 | 0 | 3 | 45 ppb |
| Green River Mutual Water Co. CA4000554 | 350 | 0 | 0 | 2 | 0.5 ppb |
| Rancho Colina Mobile Home Park CA4000653 | 252 | 0 | 0 | 1 | 0 ppb |
| Halcyon Water System CA4000501 | 110 | 0 | 0 | 1 | 0 ppb |
ZIP reports in San Luis Obispo County
No ZIP report in this county is published yet.
These ZIP codes are covered by this overview because their utility has too little EPA data for a separate page: 93407, 93408, 93410, 93432.
Sources and scope
EPA UCMR 5 occurrence data, samples collected 2023-01-03 – 2026-06-17, final release, August 2026 (file dated Aug 28, 2026); EPA SDWIS via ECHO, 2026Q2 extract (file dated Jul 9, 2026); EPA service-area boundaries v3.0; Census 2020 ZCTAs. Page generated 2026-09-03.
Counts cover the systems that report this county to EPA. A water system may cross county lines. "Found" means at least one result at or above the laboratory reporting level; it is not a compliance finding.