How many water violations are in Napa County?

Napa County has 2,698 total drinking water violations across 185 water systems, of which 566 are health-based violations. 88.1% of systems have at least one violation.

How many people get water from Napa County systems?

Water systems in Napa County serve approximately 161,964 people through 185 public water systems.

Has PFAS been detected in Napa County water?

Under EPA UCMR5, 1 of 5 tested systems in Napa County had at least one PFAS detection (20.0% of the UCMR5-tested subset - not of all 185 SDWIS systems).

What types of water sources supply Napa County?

Water systems in Napa County use GW (165 systems), SW (20 systems) as their primary water sources.

Are health-based violations serious?

Health-based violations indicate that drinking water exceeded Maximum Contaminant Levels (MCLs) set by the EPA or failed treatment technique requirements. 21.0% of Napa County's violations are health-based. Among counties with any SDWIS violations, this extract puts Napa County in the middle health-based share band. Not all violations indicate immediate health risk, but they require corrective action.

Where does Napa County sit among U.S. counties for water-system population?

According to EPA SDWIS county population served used on /counties, Napa County ranks #397 of 3,254 counties by people served, and #33 of 58 counties in California. Ordinals use the same total_population DESC sort as the counties directory. See /methodology#corpus-placement.

Counties → California

Napa County, California

Compiled by PlainWater · May 15, 2026

SDWIS compliance plate

Sheet CA055 · Napa County 185 sys · 2,698 viol · #397/3254

VIOL-SEVERE · HEALTH-MID · RANK-TOP · PHOTO-FINISH · PFAS-LOW · SRC-GW · SYS-LARGE · BOOK-FULL

VIOL-SEVERE 88.1% flagged
HEALTH-MID 21.0% health
RANK-TOP #397/3254
PHOTO-FINISH ±0.2 pp
PFAS-LOW 20.0% detect
SRC-GW GW lead 89%
SYS-LARGE 185 systems
BOOK-FULL 7/7 fields

Nearest flagged-rate peer: Sacramento County ( -0.2 pp flagged-rate)

According to EPA SDWIS county population served used on /counties, Napa County ranks #397 of 3,254 counties by people served, and #33 of 58 counties in California. See methodology · corpus placement.

Napa County standing, lower-flagged corpus third

Flagged-system rate 88.1% is at or below the corpus lower third (≤ 92.7% flagged) across 2,973 counties with ≥3 SDWIS systems . Health-based share 21.0% is health-based share in the middle third (≤ 24.5%) . UCMR5 detect rate 20.0% is UCMR5 detect rate in the tested-pool middle third (≤ 33.3%) . Population served ranks #397 of 3,254 · #33 of 58 in California.

Water Systems

System Name	Population	Violations	PFAS
Napa, City Of	84,804	23	Clean
American Canyon, City Of	21,437	33	Clean
Phelps Vineyards	19,412	14	-
Calistoga, City Of	5,610	32	Detected
St. Helena, City Of	5,386	23	Clean
Town of Yountville	2,787	8	Clean
Pacific Union College	1,958	9	-
Howell Mountain Mutual Water Company	1,240	92	-
Veterans Home of California	1,000	9	-
Castello Di Amorosa	833	13	-
Adventist Health - St. Helena Hospital	817	7	-
Berryessa Highlands	715	59	-
Domaine Carneros	652	8	-
Csp-Bothe-Napa Valley State Park	565	4	-
Circle Oaks Water District	500	7	-
Raymond Vineyard & Cellar	490	6	-
Berryessa Estates (Lbrid)	474	54	-
Sutter Home Winery	417	0	-
Napa Valley Country Club	400	8	-
Hillside Christian Center Water System	311	0	-
Beringer Vineyards	300	12	-
Berryessa Pines Water System	261	29	-
Meyers Water Co.	250	38	-
Hess Winery	250	15	-
Bella Union Winery	238	19	-
Rutherford Hill Mutual Water	232	10	-
Spanish Flat Water District	230	21	-
Capell Valley Estates	208	58	-
Enchanted Hills	206	15	-
Bell Wine Cellars	200	0	-
Tucker Acres Mutual Water Co.	200	35	-
Tpwc Dba the Prisoner Wine Company	200	6	-
Welcome Grange Hall	200	35	-
Putah Canyon Campground	200	39	-
Domaine Chandon	200	41	-
The Ranch Winery	200	19	-
Silver Oak Wine Cellars	188	10	-
Csp - Bale Grist Mill State Historic Par	185	5	-
Schramsberg Winery	161	17	-
Clos Pegase Winery	155	17	-
Rombauer Vineyards	150	14	-
Skyline Park	150	16	-
Nickel & Nickel Winery	148	8	-
Syar Industries	130	18	-
Milat Winery	128	5	-
Chateau Montelena Winery	125	12	-
Chimney Rock Winery	122	6	-
Lewis Cellars	119	15	-
One Hope Winery	110	3	-
Baldacci Family Vineyards	110	0	-

Compare beyond California

Lower-flagged peers for Napa County

Cross-state counties nearest Napa County on flagged-system share (88.1%) and cumulative violation count (2,698). In-state neighbours stay on the compliance plate above.

Similar flagged-system rate

Nearest cross-state counties by % of SDWIS systems with at least one violation on record.

4 peers

Similar violation load

Nearest cross-state counties by cumulative SDWIS violation count (all systems in the county).

4 peers

Read our methodology · Check your water system - how this data is sourced, computed, and verified.

Data sourced from EPA SDWIS and UCMR5 PFAS monitoring data. See our methodology for details. Retrieved and formatted by PlainWater

Compiled by PlainWater, Drinking Water Quality Editorial Process · May 15, 2026

Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This page draws directly on EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.