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Little Potato Slough Mutual

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
560 people
Connections
202
Water source
Surface water
Based in
Lodi, CA
County
San Joaquin
Owner
Private
Hardness
Soft
The ZIP code it serves

95242

The short answer

1 result is above EPA’s legal limit. The worst: Total trihalomethanes (TTHM), above the legal limit. 5 health-based violations since 2016.

What handles it

What was found

Total trihalomethanes (TTHM), haloacetic acids (HAA5), nitrate, arsenic, chromium (total) and fluoride: California’s own results, samples taken from Jan. 6, 2020 to June 1, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the legal limit1

Total trihalomethanes (TTHM)

Forms or is added in treatment

Above the legal limit

82.6ppb

Highest yearly average, 2020 to 2026

2026 average: 31.2 ppb

Averaged by year, the highest was 82.6 ppb, in 2021, above EPA’s legal limit of 80 ppb. Its highest single sample was 123 ppb. In 2026, the latest year on file, its six samples averaged 31.2 ppb. EPA recorded a violation for total trihalomethanes (TTHM) at this utility in 2021. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 79.3 ppb, in 2018.

What handles it

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

Below EPA’s limits2

Haloacetic acids (HAA5)

Forms or is added in treatment

Below EPA’s limits

51ppb

Highest yearly average, 2020 to 2026

2026 average: 26.3 ppb

Averaged by year, the highest was 51 ppb, in 2021, below EPA’s legal limit of 60 ppb. Its highest single sample was 104 ppb. In 2026, the latest year on file, its six samples averaged 26.3 ppb. 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 79.5 ppb, in 2018, and EPA recorded violations in 2016 and 2019.

What handles it

No certification claim covers this compound yet.

Nitrate

Comes from the source

Below EPA’s limits

0.6ppm

Highest sample; found in 2 of 7

2025 average: 0.2 ppm

The highest sample, in 2021, was 0.6 ppm, below EPA’s legal limit of 10 ppm. In 2025, the latest year on file, its two samples averaged 0.2 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 0.75 ppm, in 2014.

What handles it

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

    For: Total trihalomethanes (TTHM)

    Other certifiers’ wording: VOC Reduction

  • NSF/ANSI 58

    Claim: Trihalomethanes (TTHM) Reduction

    For: Total trihalomethanes (TTHM)

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

Hardness

Soft, 55 mg/L (3.2 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 3.2 grains per gallon, salt includedSoftener or salt-free conditioner?California water hardness, utility by utility

Violations since 2016

Contaminant or ruleTypePeriodMeasuredStatus
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2021 to Dec. 31, 20210.081 MG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2019 to Sept. 30, 20190.068 MG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2019 to June 30, 20190.071 MG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2019 to March 31, 20190.069 MG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2016 to June 30, 20160.065 MG/LResolved
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. Total trihalomethanes (TTHM), haloacetic acids (HAA5), nitrate, arsenic, chromium (total) and fluoride results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Little Potato Slough Mutual’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. 6, 2020 to June 1, 2026.

Testing your own tap

Little Potato Slough Mutual’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 Little Potato Slough Mutual serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Lodi Wine Laboratories

    Lodi, CA · about 7 miles

    Certified for nitrate, minerals and other inorganics

    (209) 339-1990

  • Precision Enviro-Tech

    Stockton, CA · about 11 miles

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

    (209) 405-0601

  • San Joaquin County Public Health Laboratory

    Stockton, CA · about 14 miles

    Certified for bacteria

    (209) 468-3460

All 145 certified labs for California

Sources

PWSID CA3910022. Rebuilt from EPA data on Oct. 18, 2026.

Towns it serves

Also in San Joaquin County

All California utilities

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