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Lower Lake County 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
1,326 people
Connections
863
Water source
Groundwater
Based in
Lower Lake, CA
County
Lake
Owner
Local government
Hardness
Varies by source
The ZIP code it serves

95457

The short answer

1 result is above the health goal. The worst: Arsenic, above the health goal. 1 health-based violation since 2016.

What handles it

What was found

Arsenic, nitrate, total trihalomethanes (TTHM), haloacetic acids (HAA5), fluoride, chromium (total) and uranium: California’s own results, samples taken from Jan. 2, 2020 to June 10, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the health goal1

Arsenic

Comes from the source

Above the health goal

6.5ppb

Highest yearly average, 2020 to 2026

2026 average: 4.3 ppb

Averaged by year, the highest was 6.5 ppb, in 2020: below EPA’s legal limit of 10 ppb, but above its health goal of zero. Its highest single sample was 35 ppb. In 2026, the latest year on file, its 11 samples averaged 4.3 ppb. EPA recorded no violation for arsenic at this utility since 2020. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 9.1 ppb, in 2016.

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 limits4

Nitrate

Comes from the source

Below EPA’s limits

8.8ppm

Highest sample; found in 27 of 63

2026 average: 4.4 ppm

The highest sample, in 2024, was 8.8 ppm, below EPA’s legal limit of 10 ppm. In 2026, the latest year on file, its three samples averaged 4.4 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 8.0 ppm, in 2019.

What handles it

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

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

54.2ppb

Highest yearly average, 2020 to 2025

Averaged by year, the highest was 54.2 ppb, in 2025, below EPA’s legal limit of 80 ppb. Its highest single sample was 67.6 ppb. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 73.7 ppb, in 2012.

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

25.5ppb

Highest yearly average, 2020 to 2025

2025 average: 23.1 ppb

Averaged by year, the highest was 25.5 ppb, in 2021, below EPA’s legal limit of 60 ppb. Its highest single sample was 36.6 ppb. In 2025, the latest year on file, its two samples averaged 23.1 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 30.1 ppb, in 2019.

What handles it

No certification claim covers this compound yet.

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.41ppm

Highest yearly average, 2020 to 2026

2026, one sample: 0.3 ppm

Averaged by year, the highest was 0.41 ppm, in 2021, below EPA’s legal limit of 4.0 ppm. Its highest single sample was 0.48 ppm. In 2026, the latest year on file, its one sample was 0.3 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.44 ppm, in 2012.

What handles it

3 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Chromium (total)
  • Lead
  • Uranium

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

    Claim: Arsenic (Pentavalent)<=50 ppb Reduction

    For: 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 reverse osmosis systems, ranked

Hardness

Hard to very hard depending on the source, 141 to 476 mg/L (8.2 to 27.8 grains per gallon), across 8 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

Contaminant or ruleTypePeriodMeasuredStatus
Groundwater RuleA significant problem found in a state inspection was not fixed on time.EPA: Failure To Address DeficiencyJune 20, 2023—Resolved
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 1 monitoring or reporting violation not shown.

What this report can’t tell you

  • Everything else. Arsenic, nitrate, total trihalomethanes (TTHM), haloacetic acids (HAA5), fluoride, chromium (total) and uranium results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Lower Lake County 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 Jan. 2, 2020 to June 10, 2026.

Testing your own tap

Lower Lake County 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 Lower Lake County Water District serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • K Prime, LLC.

    Santa Rosa, CA · about 30 miles

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

    (707) 527-7574

  • Sonoma County Public Health Laboratory

    Santa Rosa, CA · about 30 miles

    Certified for bacteria

    (707) 565-4711

  • Brelje and Race Laboratories, Inc.

    Santa Rosa, CA · about 32 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 CA1710010. Rebuilt from EPA data on Oct. 18, 2026.

Towns it serves

Also in Lake County

All California utilities

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