Skip to content
TapBuff
ZIP

College Park Mutual Water Company

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
244 people
Connections
75
Water source
Groundwater
Based in
Penngrove, CA
County
Sonoma
Owner
Private
Hardness
Varies by source
The ZIP code it serves

94951

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: Arsenic, above the limit’s level, no violation. No health-based violations on file since 2016.

What handles it

What was found

Arsenic, uranium, fluoride, total trihalomethanes (TTHM), chromium (total), haloacetic acids (HAA5) and nitrate: California’s own results, samples taken from June 10, 2020 to June 16, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the limit’s level, no violation recorded1

Arsenic

Comes from the source

Above the limit’s level, no violation

27.7ppb

Highest yearly average, 2020 to 2026

2026: not found

Averaged by year, the highest was 27.7 ppb, in 2021, about 2.8 times EPA’s legal limit of 10 ppb. Its highest single sample was 46 ppb. In 2026, 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 arsenic 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. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 12 ppb, in 2012.

What handles it

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

Above the health goal1

Uranium

Comes from the source

Above the health goal

1.8ppb

Highest yearly average, 2025

Averaged by year, the highest was 1.8 ppb, in 2025: below EPA’s legal limit of 30 ppb, but above its health goal of zero. That is the only year on file.

What handles it

Below EPA’s limits2

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.58ppm

Highest yearly average, 2020 to 2026

2026, one sample: 0.12 ppm

Averaged by year, the highest was 0.58 ppm, in 2022, below EPA’s legal limit of 4.0 ppm. In 2026, the latest year on file, its one sample was 0.12 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.59 ppm, in 2013.

What handles it

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

1.3ppb

Highest yearly average, 2020 to 2023

2023: not found

Averaged by year, the highest was 1.3 ppb, in 2020, below EPA’s legal limit of 80 ppb. Its highest single sample was 2.7 ppb. In 2023, 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 2.0 ppb, in 2014.

What handles it

  • NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
  • NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”
4 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Chromium (total)
  • Haloacetic acids (HAA5)
  • Lead
  • Nitrate

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

    Claim: Arsenic (Pentavalent)<=50 ppb Reduction

    For: Arsenic

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

  • NSF/ANSI 58

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

    For: Arsenic, Uranium

    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 reverse osmosis systems, ranked

Hardness

Hard to very hard depending on the source, 130 to 200 mg/L (7.6 to 11.7 grains per gallon), across 3 sampling points, 2019 to 2026.

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, 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. There are 2 monitoring or reporting violations: a sample missed, late or not reported.

What this report can’t tell you

  • Everything else. Arsenic, uranium, fluoride, total trihalomethanes (TTHM), chromium (total), haloacetic acids (HAA5) and nitrate results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. College Park Mutual Water Company’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 June 10, 2020 to June 16, 2026.

Testing your own tap

College Park Mutual Water Company’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 College Park Mutual Water Company serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Alpha Analytical Laboratories Inc. - North Bay

    Petaluma, CA · about 4 miles

    Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, PFAS

    (707) 769-3128

  • Brelje and Race Laboratories, Inc.

    Santa Rosa, CA · about 9 miles

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

    (707) 544-8807

  • Sonoma County Public Health Laboratory

    Santa Rosa, CA · about 11 miles

    Certified for bacteria

    (707) 565-4711

All 145 certified labs for California

Sources

PWSID CA4900667. Rebuilt from EPA data on Oct. 18, 2026.

Towns it serves

Also in Sonoma County

All California utilities

What to do next