Skip to content
TapBuff
ZIP

Mondavi Farm Worker Center

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
66 people
Connections
3
Water source
Groundwater
Based in
Napa, CA
County
Napa
Owner
Local government
Hardness
Very hard
The ZIP code it serves

94558

The short answer

1 result is above EPA’s legal limit, and 1 more is above the health goal. The worst: Lead, above the action level. No health-based violations on file since 2016.

What handles it

What was found

Lead and copper: EPA SDWIS monitoring periods ending 2010 to 2026.

Arsenic, nitrate, fluoride, chromium (total) and total trihalomethanes (TTHM): California’s own results, samples taken from May 13, 2020 to May 6, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the legal limit1

Lead

Comes from pipes, often your own

Above the action level

33ppb

90th percentile, 2024 to 2026

In the latest period, 9 in 10 homes sampled were at or below 33 ppb, above EPA’s action level of 15 ppb. The action level drops to 10 ppb on Nov. 1, 2027, and this result is at or above that. EPA’s health goal for lead is zero.

What handles it

Above the health goal1

Arsenic

Comes from the source

Above the health goal

5.2ppb

Highest yearly average, 2022 to 2025

Averaged by year, the highest was 5.2 ppb, in 2025: below EPA’s legal limit of 10 ppb, but above its health goal of zero. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 5.0 ppb, in 2013.

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 limits2

Nitrate

Comes from the source

Below EPA’s limits

1.8ppm

Highest sample; found in 8 of 9

2026, one sample: 0.93 ppm

The highest sample, in 2020, was 1.8 ppm, below EPA’s legal limit of 10 ppm. In 2026, the latest year on file, its one sample was 0.93 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 1.9 ppm, in 2017.

What handles it

  • NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
  • NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.55ppm

Highest yearly average, 2022 to 2025

Averaged by year, the highest was 0.55 ppm, in 2025, below EPA’s legal limit of 4.0 ppm. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.8 ppm, in 2013.

What handles it

2 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Chromium (total)
  • Total trihalomethanes (TTHM)

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: Lead Reduction, Arsenic (Pentavalent)<=50 ppb Reduction

    For: Lead, Arsenic

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

  • NSF/ANSI 58

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

    For: Lead, Arsenic

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

At the tap, or for the whole house?

Lead and copper usually come from pipes and fixtures inside or near your home. A whole-house system sits where water enters, so it cannot catch what your own plumbing adds after it. For those, the filter that counts is the one at the tap. 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 lead, ranked

The best reverse osmosis systems, ranked

Hardness

Very hard, 310 mg/L (18.1 grains per gallon), at its one sampling point, 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 18.1 grains per gallon, salt includedSoftener or salt-free conditioner?California water hardness, utility by utility

Violations since 2016

No health-based violations on file with EPA since 2016.

What this report can’t tell you

  • Everything else. Arsenic, nitrate, fluoride, chromium (total) and total trihalomethanes (TTHM) results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Mondavi Farm Worker Center’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 May 13, 2020 to May 6, 2026.

Testing your own tap

Mondavi Farm Worker Center’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 Mondavi Farm Worker Center 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 CA2800040. Rebuilt from EPA data on Oct. 18, 2026.

Towns it serves

Also in Napa County

All California utilities

What to do next