County · California
San Luis Obispo County, California: drinking water records
Explore EPA records for 73 community water systems across 23 ZIP codes in San Luis Obispo County, then find water-testing resources and available recent monitoring-station readings.
Data as of EPA UCMR 5 final release, August 2026 (file dated Aug 28, 2026) · EPA SDWIS 2026Q2 (file dated Jul 9, 2026). How we build these pages
Drinking-water records
EPA survey and compliance records are historical reports. UCMR 5 results are available for 17 of the 73 listed systems in this snapshot. A system with no reported PFAS detection is not a test of every tap or every contaminant.
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 in this county
All 73 active community systems in the available county records, sorted by record completeness. Scroll the table to explore more systems.
| 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 ppbbelow the action level |
| Cambria Comm Services Dist CA4010014 | 5,532 | 120 | 0 | 2 | 0 ppbbelow the action level |
| Heritage Ranch CSD CA4010012 | 2,956 | 120 | 0 | 15 | 0 ppbbelow the action level |
| San Luis Obispo Water Department CA4010009 | 47,788 | 120 | 0 | 0 | 0 ppbbelow the action level |
| City of Paso Robles Water Division CA4010007 | 31,176 | 780 | 7 | 0 | 0 ppbbelow the action level |
| Atascadero Mutual Water Co CA4010002 | 30,618 | 240 | 5 | 0 | 0 ppbbelow the action level |
| City of Arroyo Grande Utilities Division CA4010001 | 17,963 | 240 | 6 | 0 | 0 ppbbelow the action level |
| California Mens Colony CA4010830 | 15,000 | 125 | 0 | 0 | 0 ppbbelow the action level |
| Nipomo Comm Services Dist CA4010026 | 13,771 | 360 | 0 | 0 | 0 ppbbelow the action level |
| Morro Bay Pw Dept - Water Division CA4010011 | 13,757 | 120 | 0 | 0 | 0 ppbbelow the action level |
| City of Grover Beach Public Works Dept CA4010004 | 12,701 | 180 | 0 | 0 | 0 ppbbelow the action level |
| Templeton CSD CA4010019 | 8,011 | 270 | 2 | 0 | 0 ppbbelow the action level |
| Oceano Comm Services Dist. CA4010005 | 7,601 | 240 | 0 | 0 | 0 ppbbelow the action level |
| Los Osos Community Services District CA4010016 | 7,086 | 420 | 8 | 0 | 0 ppbbelow the action level |
| Golden State Water Company - Los Osos CA4010017 | 5,924 | 240 | 4 | 0 | 0 ppbbelow the action level |
| Golden State Water Company - Nipomo CA4010018 | 4,506 | 180 | 1 | 0 | 5.2 ppbbelow the action level |
| Atascadero State Hospital CA4010832 | 4,100 | 60 | 5 | 0 | 0 ppbbelow the action level |
| Nacimiento Water Company CA4010027 | 2,181 | 0 | 0 | 21 | 0 ppbbelow the action level |
| San Miguelito Mwc CA4010003 | 1,600 | 0 | 0 | 2 | 0 ppbbelow the action level |
| Lopez Project CA4010022 | 1,569 | 0 | 0 | 1 | 0.8 ppbbelow the action level |
| Woodland Park Mutual Water Co CA4000506 | 538 | 0 | 0 | 12 | 12 ppbbelow the action level |
| San Simeon CSD CA4000568 | 462 | 0 | 0 | 3 | 45 ppbat or above the action level |
| Green River Mutual Water Co. CA4000554 | 350 | 0 | 0 | 2 | 0.5 ppbbelow the action level |
| Rancho Colina Mobile Home Park CA4000653 | 252 | 0 | 0 | 1 | 0 ppbbelow the action level |
| Halcyon Water System CA4000501 | 110 | 0 | 0 | 1 | 0 ppbbelow the action level |
| Resthaven Mobile Home Park CA4000654 | 99 | 0 | 0 | 21 | 0 ppbbelow the action level |
| Ken Mar Gardens CA4000648 | 84 | 0 | 0 | 22 | 0 ppbbelow the action level |
| Country Hills Estates CA4000637 | 60 | 0 | 0 | 11 | 17 ppbat or above the action level |
| Rim Rock Water Company CA4000750 | 55 | 0 | 0 | 31 | 0 ppbbelow the action level |
| Almira Water Association CA4000631 | 40 | 0 | 0 | 14 | 0 ppbbelow the action level |
| Higuera Apartments CA4000563 | 30 | 0 | 0 | 22 | 11 ppbbelow the action level |
| Mustang Springs Mutual Water CA4000775 | 30 | 0 | 0 | 2 | 0 ppbbelow the action level |
| Woodlands Development CA4010081 | 3,862 | 0 | 0 | 0 | 0 ppbbelow the action level |
| San Miguel Community Services District CA4010010 | 2,600 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Cayucos Beach Mutual Water Company CA4010006 | 2,567 | 0 | 0 | 0 | 0.6 ppbbelow the action level |
| Morro Rock Mutual Water Co CA4010015 | 2,181 | 0 | 0 | 0 | 0.8 ppbbelow the action level |
| Golden State Water Company-Cypress Ridge CA4010040 | 2,026 | 0 | 0 | 0 | 1.5 ppbbelow the action level |
| Avila Beach Community Services District CA4000222 | 1,630 | 0 | 0 | 0 | 1.1 ppbbelow the action level |
| Golden State Water Company - Edna CA4010023 | 1,493 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Slo Cwwd No. 23 - Santa Margarita CA4010024 | 1,291 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Slocsa #10a - Cayucos CA4010901 | 1,200 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Slo Csa No. 16 - Shandon CA4010028 | 1,085 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Laureate Water Company CA4000206 | 700 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Mesa Dunes Mobile Home Estates CA4000650 | 600 | 0 | 0 | 0 | 2.2 ppbbelow the action level |
| S & T Mutual Water Company CA4000523 | 591 | 0 | 0 | 0 | 1.1 ppbbelow the action level |
| Walnut Hills Mutual Water Co CA4000670 | 486 | 0 | 0 | 0 | 5.2 ppbbelow the action level |
| Garden Farms C.W.D. CA4000507 | 440 | 0 | 0 | 0 | 11 ppbbelow the action level |
| Los Robles Mobile Home Estates CA4000649 | 420 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Santa Ysabel Ranch Mwc CA4000802 | 344 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Irish Hills Mutual Water Co CA4000203 | 135 | 0 | 0 | 0 | 2.8 ppbbelow the action level |
| Canyon Crest Mutual Benefit Wc CA4000230 | 133 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Edna Valley Ranch East CA4000202 | 132 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Callender Grove Mutual Water CA4000805 | 126 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Spanish Lakes Mutual Water Co CA4000789 | 125 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Las Ventanas Ranch CA4000815 | 108 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Varian Ranch Mutual Water CA4000765 | 105 | 0 | 0 | 0 | 8.5 ppbbelow the action level |
| Afuera de Chorro Water Company CA4000744 | 85 | 0 | 0 | 0 | 2.8 ppbbelow the action level |
| Bassi Ranch Mutual Water Co. CA4000200 | 85 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Baron Canyon Mutual Water Co. CA4000214 | 81 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Laguna Negra Mutual Water Co. CA4000705 | 80 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Avila Valley Mutual Water Co CA4000716 | 75 | 0 | 0 | 0 | 3.2 ppbbelow the action level |
| H2o, INC CA4000741 | 70 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Monte Sereno Mutual Benefit Water CA4000808 | 65 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Rancho Salinas Mbwc CA4000803 | 50 | 0 | 0 | 0 | 6.6 ppbbelow the action level |
| Bear Valley Water Company CA4000660 | 45 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Rancho Nipomo Water Company CA4000771 | 44 | 0 | 0 | 0 | 3.2 ppbbelow the action level |
| Terra de Oro Water Company CA4000749 | 38 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Ada'S Lodges CA4000839 | 25 | 0 | 0 | 0 | 0 ppbbelow the action level |
| Slo Csa No. 10 - Cayucos WTP CA4010025 | 0 | 0 | 0 | 0 | 5.3 ppbbelow the action level |
| Gran Cielo Mutual Water Company CA4000853 | 139 | 0 | 0 | 0 | not reported |
| Anza Vineyard Estates Mutual Water Co CA4000834 | 60 | 0 | 0 | 0 | not reported |
| Chorro Valley Pipeline - Slo County CA4010030 | 0 | 0 | 0 | 0 | not reported |
| Nacimiento Water Project CA4010080 | 0 | 0 | 0 | 0 | not reported |
Shaded rows report lead at or above the 15 ppb action level in their latest monitoring period. EPA sets that level for the value 9 in 10 sampled homes fall at or below; reaching it requires the utility to act, and it is not a measurement of any single tap. 2 systems in this table are at or above it. What an action level means
USGS · Monitoring stations
The water, more recently.
Available station readings in San Luis Obispo County, California. Each measurement keeps its time, unit and original source.
These readings describe water at a monitoring station. They do not test your tap, measure PFAS or lead, or determine whether water is safe to drink or swim in.
Recent observations load when this section comes into view.
How these readings update
We check for updates every 10 minutes while this section is visible and show supported observations from the last 48 hours. The time beside a reading is when USGS measured it; the checked time is when our service retrieved the response. We mark a reading more than 6 hours old as older. Provisional observations can change after USGS review. A missing reading does not mean zero or clean water.
Temperature, pH, dissolved oxygen, turbidity, conductivity, streamflow and water level are shown only where a station reports them. Different measurements have different units and sampling intervals. USGS data and documentation.
Your next step
Water testing, reports & local help.
Use these official directories to find your drinking-water agency, a certified laboratory and public water records. We have not yet added an individually reviewed local resource list for this county.
Official national directories
Water testing
Find your state’s private-well program
EPA’s state directory points well owners to local program information. Services and eligibility vary by state and county.
Water testing
Find a certified drinking-water laboratory
Use EPA’s directory to reach your state’s laboratory certification program. EPA does not provide on-request testing of residential drinking water.
Public records
Find your utility’s Consumer Confidence Report
EPA links to community water-system reports and explains how to read them. Look for your actual supplier rather than assuming every address in a county shares one system.
Public records
Explore USGS water observations
Find current and historical observations from USGS monitoring locations, including available stream, lake, and groundwater data. Measurements vary by station and do not replace a test of your household water.
A county overview cannot identify every property’s water provider. If you use a public water system, confirm its name on your bill and request its annual Consumer Confidence Report. Private wells need their own testing; public-system records do not describe a private well.
Understand water testing and laboratory reportsResource descriptions are compiled by Tap Water Lookup. Review dates describe our source check, not a new water sample. How we review sources · Suggest a correction
Explore your area
Local coverage in San Luis Obispo County
23ZIP areas in this overview
Explore the water-system records, recent station readings and testing resources on this county page. They describe the systems and stations identified in each section; they are not a separate water test for every community.
Towns and communities
- Arroyo Grande
- Atascadero
- Avila Beach
- California Polytechnic State University
- Cambria
- Cayucos
- Creston
- El Paso de Robles (Paso Robles)
- Grover Beach
- Los Osos
- Morro Bay
- Nipomo
- Oceano
- Pismo Beach
- San Luis Obispo
- San Simeon
- Santa Margarita
- Shandon
- Templeton
View ZIP areas and understand coverage
- 93401San Luis Obispo
- 93402Los Osos
- 93405San Luis Obispo
- 93407California Polytechnic State University
- 93408
- 93409
- 93410California Polytechnic State University
- 93420Arroyo Grande
- 93422Atascadero
- 93424Avila Beach
- 93428Cambria
- 93430Cayucos
- 93432Creston
- 93433Grover Beach
- 93442Morro Bay
- 93444Nipomo
- 93445Oceano
- 93446El Paso de Robles (Paso Robles)
- 93449Pismo Beach
- 93452San Simeon
- 93453Santa Margarita
- 93461Shandon
- 93465Templeton
These Census ZIP Code Tabulation Areas are grouped here by their largest county overlap. A ZIP area can cross county lines and contain several water suppliers or private wells. Place labels reflect Census geography, not verified postal city names or utility service boundaries.
Records for these areas are currently presented in this county overview rather than individual ZIP reports. An unpublished report does not mean there are no water records. Confirm your supplier on your water bill; if you use a private well, testing your own well is the relevant next step.
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. Database prepared 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.
Compiled by Tap Water Lookup from the sources identified on this page. Read the methodology and review process.