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Spanish Flat Water District

What EPA’s and California’s records show in this utility’s water: nitrate, arsenic and other regulated chemicals; lead and copper; and violations since 2016, with the certification that handles each result.

Serves
92 people
Connections
35
Water source
Surface water
Based in
Napa, CA
County
Napa
Owner
Local government
Hardness
Hard
The ZIP code it serves

94558

The short answer

1 result is above the limit’s level with no violation recorded, and 1 more is above the health goal. The worst: Fluoride, above the limit’s level, no violation. 1 health-based violation since 2016.

What handles it

What was found

Fluoride, arsenic, total trihalomethanes (TTHM), haloacetic acids (HAA5), nitrate and chromium (total): California’s own results, samples taken from March 26, 2020 to Dec. 16, 2025, with EPA’s 2012 to 2019 file for earlier years.

Above the limit’s level, no violation recorded1

Fluoride

Forms or is added in treatment

Above the limit’s level, no violation

24ppm

Highest yearly average, 2021 to 2025

2025: not found

Averaged by year, the highest was 24 ppm, in 2022, about 6 times EPA’s legal limit of 4.0 ppm. In 2025, the latest year on file, it wasn’t found in its one sample. EPA judges this limit on running averages at each sampling point, and recorded no violation for fluoride at this utility since 2020. Results like these with no violation often include water sampled before treatment or blending; the utility’s annual report says what reaches the tap.

What handles it

Above the health goal1

Arsenic

Comes from the source

Above the health goal

2.9ppb

Highest yearly average, 2020 to 2025

2025: not found

Averaged by year, the highest was 2.9 ppb, in 2022: below EPA’s legal limit of 10 ppb, but above its health goal of zero. In 2025, the latest year on file, it wasn’t found in its one sample. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 3.0 ppb, in 2014.

What handles it

  • NSF/ANSI 58 look for “Arsenic (Pentavalent)<=50 ppb Reduction”
  • NSF/ANSI 53 look for “Arsenic (Pentavalent)<=50 ppb Reduction”

Below EPA’s limits3

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

77.3ppb

Highest yearly average, 2020 to 2025

2025 average: 58 ppb

Averaged by year, the highest was 77.3 ppb, in 2024, below EPA’s legal limit of 80 ppb. Its highest single sample was 85 ppb. In 2025, the latest year on file, its two samples averaged 58 ppb. EPA recorded no violation for total trihalomethanes (TTHM) at this utility since 2020. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 78 ppb, in 2016.

What handles it

  • NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
  • NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”

Haloacetic acids (HAA5)

Forms or is added in treatment

Below EPA’s limits

45.5ppb

Highest yearly average, 2020 to 2025

Averaged by year, the highest was 45.5 ppb, in 2025, below EPA’s legal limit of 60 ppb. Its highest single sample was 70 ppb. That was also the latest year on file. EPA recorded no violation for haloacetic acids (HAA5) at this utility since 2020. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 22.8 ppb, in 2013.

What handles it

No certification claim covers this compound yet.

Nitrate

Comes from the source

Below EPA’s limits

0.12ppm

Highest sample; found in 1 of 7

2025: not found

The highest sample, in 2024, was 0.12 ppm, below EPA’s legal limit of 10 ppm. In 2025, the latest year on file, it wasn’t found in its one sample. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 0.19 ppm, in 2019.

What handles it

  • NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
  • NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”
2 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Chromium (total)
  • Lead

What handles it

A certification covers specific claims, not a whole standard. Look for these claims on the certifier’s listing, not the box. Wording varies a little: NSF writes “Lead Reduction,” WQA just “Lead.”

  • NSF/ANSI 53

    Claims: Fluoride, Arsenic (Pentavalent)<=50 ppb Reduction

    For: Fluoride, Arsenic

    Other certifiers’ wording: Arsenic (III) (50 ppb influent level)

  • NSF/ANSI 58

    Claims: Fluoride Reduction, Arsenic (Pentavalent)<=50 ppb Reduction

    For: Fluoride, Arsenic

    Other certifiers’ wording: Arsenic (Pentavalent)<=300 ppb Reduction; Arsenic (V) (300 ppb influent level)

At the tap, or for the whole house?

These come with the water itself, so a whole-house system certified for the same claims treats every tap and shower. A filter at the tap treats drinking water for much less. How whole-house systems compare.

Filters with those claims on a certifier’s listing

Disclosure: TapBuff earns a commission if you buy through some links on this page. It does not change which standard or filter we name. As an Amazon Associate, TapBuff earns from qualifying purchases. How TapBuff makes money

Compare five-year costs

The best water filters for fluoride, ranked

The best reverse osmosis systems, ranked

Hardness

Hard, typically 170 mg/L (9.9 grains per gallon), across 2 sampling points, 2019 to 2025.

Hardness is calcium and magnesium. EPA sets no limit for it: it shows up as scale on fixtures and in water heaters, and as soap that won’t lather. USGS calls water above 60 mg/L moderately hard, above 120 hard and above 180 very hard.

Softeners compared at 9.9 grains per gallon, salt includedSoftener or salt-free conditioner?California water hardness, utility by utility

Violations since 2016

Contaminant or ruleTypePeriodMeasuredStatus
Lead and Copper Rule RevisionsThe required inventory of lead service lines was not completed or submitted on time.EPA: LSL InventoryOct. 17, 2024—Unaddressed
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 6 monitoring or reporting violations not shown.

What this report can’t tell you

  • Everything else. Fluoride, arsenic, total trihalomethanes (TTHM), haloacetic acids (HAA5), nitrate and chromium (total) results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Spanish Flat Water District’s own annual report, which it must send you every year, has the contaminants this page does not show.

  • Your own plumbing. Lead results are the 90th percentile across homes the utility samples. Your home’s service line, solder and fixtures decide yours. A certified lab test is the only way to know.

  • What it means for your health. This page reports what the records show and EPA’s limits and goals; it is not medical advice. If you are worried about a health effect, talk to a doctor or your local health department.

  • Anything after the latest data. SDWIS data is from 2026 Q3; UCMR 5 didn’t sample this utility; California’s results run from March 26, 2020 to Dec. 16, 2025.

Testing your own tap

Spanish Flat Water District’s results are for the water it sends out. What your own service line, solder and fixtures add shows up only in a test of your tap, by a lab California certifies.

The 3 labs California certifies closest to the area Spanish Flat Water District serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Caltest Analytical Laboratory

    Napa, CA · about 15 miles

    Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, organic chemicals, disinfection byproducts

    (707) 258-4000

  • Napa-Solano-Yolo-Marin Public Health Laboratory

    Fairfield, CA · about 17 miles

    Certified for bacteria

    (707) 784-4410

  • Brelje and Race Laboratories, Inc.

    Santa Rosa, CA · about 25 miles

    Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, organic chemicals, disinfection byproducts

    (707) 544-8807

All 145 certified labs for California

Sources

PWSID CA2810014. Rebuilt from EPA data on Oct. 18, 2026.

Towns it serves

Also in Napa County

All California utilities

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