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San Luis Hills

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
221 people
Connections
65
Water source
Surface water
Based in
Los Banos, CA
County
Merced
Owner
Private
Hardness
Moderately hard
The ZIP code it serves

95322

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: Haloacetic acids (HAA5), above the limit’s level, no violation. 6 health-based violations since 2016.

What handles it

What was found

Haloacetic acids (HAA5), arsenic, total trihalomethanes (TTHM), nitrate, chromium (total) and fluoride: California’s own results, samples taken from Feb. 5, 2020 to June 3, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the limit’s level, no violation recorded1

Haloacetic acids (HAA5)

Forms or is added in treatment

Above the limit’s level, no violation

78.5ppb

Highest yearly average, 2020 to 2026

Averaged by year, the highest was 78.5 ppb, in 2026, above EPA’s legal limit of 60 ppb. Its highest single sample was 84 ppb. That was also the latest year on file. EPA judges this limit on running averages at each sampling point, and recorded no violation for haloacetic acids (HAA5) 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 62.8 ppb, in 2016.

What handles it

No certification claim covers this compound yet.

Above the health goal1

Arsenic

Comes from the source

Above the health goal

3.4ppb

Highest yearly average, 2020 to 2026

2026, one sample: 2.2 ppb

Averaged by year, the highest was 3.4 ppb, in 2020: below EPA’s legal limit of 10 ppb, but above its health goal of zero. In 2026, the latest year on file, its one sample was 2.2 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 2.7 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”

Below EPA’s limits2

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

78ppb

Highest yearly average, 2020 to 2026

2026 average: 61 ppb

Averaged by year, the highest was 78 ppb, in 2025, below EPA’s legal limit of 80 ppb. Its highest single sample was 109 ppb. In 2026, the latest year on file, its two samples averaged 61 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 86.4 ppb, in 2014, and EPA recorded violations in 2014 and 2015.

What handles it

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

Nitrate

Comes from the source

Below EPA’s limits

0.45ppm

Highest sample; found in 3 of 7

2026, one sample: 0.27 ppm

The highest sample, in 2023, was 0.45 ppm, below EPA’s legal limit of 10 ppm. In 2026, the latest year on file, its one sample was 0.27 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 1.1 ppm, in 2016.

What handles it

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

    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

Moderately hard, 80 mg/L (4.7 grains per gallon), at its one sampling point, 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 at 4.7 grains per gallon, salt includedSoftener or salt-free conditioner?California water hardness, utility by utility

Violations since 2016

Contaminant or ruleTypePeriodMeasuredStatus
Total organic carbonNot enough organic matter was removed. It reacts with disinfectant to form byproducts.EPA: Treatment Technique Precursor RemovalApril 1, 2019 to June 30, 2019—Resolved
Total organic carbonNot enough organic matter was removed. It reacts with disinfectant to form byproducts.EPA: Treatment Technique Precursor RemovalOct. 1, 2018 to Dec. 31, 2018—Resolved
Total organic carbonNot enough organic matter was removed. It reacts with disinfectant to form byproducts.EPA: Treatment Technique Precursor RemovalJuly 1, 2018 to Sept. 30, 2018—Resolved
Total organic carbonNot enough organic matter was removed. It reacts with disinfectant to form byproducts.EPA: Treatment Technique Precursor RemovalApril 1, 2018 to June 30, 2018—Resolved
Total organic carbonNot enough organic matter was removed. It reacts with disinfectant to form byproducts.EPA: Treatment Technique Precursor RemovalJan. 1, 2018 to March 31, 2018—Resolved
Total organic carbonNot enough organic matter was removed. It reacts with disinfectant to form byproducts.EPA: Treatment Technique Precursor RemovalOct. 1, 2017 to Dec. 31, 2017—Resolved
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record.

What this report can’t tell you

  • Everything else. Haloacetic acids (HAA5), arsenic, total trihalomethanes (TTHM), nitrate, chromium (total) and fluoride results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. San Luis Hills’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 Feb. 5, 2020 to June 3, 2026.

Testing your own tap

San Luis Hills’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 San Luis Hills serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Certified Laboratories - Turlock

    Turlock, CA · about 23 miles

    Certified for bacteria

    (209) 664-1100

  • Microbac Laboratories, Inc. - Turlock

    Turlock, CA · about 24 miles

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

    (707) 822-4649

  • CM Analytical, Inc.

    Gilroy, CA · about 31 miles

    Certified for bacteria

    (408) 848-3619

All 145 certified labs for California

Sources

PWSID CA2400209. Rebuilt from EPA data on Oct. 18, 2026.

Also in Merced County

All California utilities

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