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Tranquillity Irrigation 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
686 people
Connections
375
Water source
Groundwater
Based in
Tranquillity, CA
County
Fresno
Owner
Local government
Hardness
Varies by source
The ZIP code it serves

93668

The short answer

1 result is above EPA’s legal limit, 1 more is above the limit’s level with no violation recorded, and 1 more is above the health goal. The worst: Arsenic, above the legal limit. 5 health-based violations since 2016.

What handles it

What was found

Arsenic, total trihalomethanes (TTHM), uranium, haloacetic acids (HAA5), fluoride, chromium (total) and nitrate: California’s own results, samples taken from Feb. 20, 2020 to June 26, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the legal limit1

Arsenic

Comes from the source

Above the legal limit

15.5ppb

Highest yearly average, 2020 to 2026

2026 average: 4.0 ppb

Averaged by year, the highest was 15.5 ppb, in 2025, above EPA’s legal limit of 10 ppb. Its highest single sample was 17 ppb. In 2026, the latest year on file, its three samples averaged 4.0 ppb. EPA recorded a violation for arsenic at this utility in 2025. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 14.2 ppb, in 2012, and EPA recorded violations in 2012, 2013 and 2014.

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 limit’s level, no violation recorded1

Total trihalomethanes (TTHM)

Forms or is added in treatment

Above the limit’s level, no violation

133ppb

Highest yearly average, 2020 to 2026

Averaged by year, the highest was 133 ppb, in 2026, above EPA’s legal limit of 80 ppb. Its highest single sample was 160 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 total trihalomethanes (TTHM) 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 100 ppb, in 2019.

What handles it

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

Above the health goal1

Uranium

Comes from the source

Above the health goal

1.6ppb

Highest yearly average, 2026

Averaged by year, the highest was 1.6 ppb, in 2026: 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

Haloacetic acids (HAA5)

Forms or is added in treatment

Below EPA’s limits

23ppb

Highest yearly average, 2020 to 2026

Averaged by year, the highest was 23 ppb, in 2026, below EPA’s legal limit of 60 ppb. Its highest single sample was 27 ppb. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 17.5 ppb, in 2019.

What handles it

No certification claim covers this compound yet.

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.88ppm

Highest yearly average, 2020 to 2026

2026, one sample: 0.33 ppm

Averaged by year, the highest was 0.88 ppm, in 2020, below EPA’s legal limit of 4.0 ppm. In 2026, the latest year on file, its one sample was 0.33 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 1.1 ppm, in 2013.

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
  • 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

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

    For: Arsenic, Total trihalomethanes (TTHM)

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

  • NSF/ANSI 58

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

    For: Arsenic, Total trihalomethanes (TTHM), 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

Soft to moderately hard depending on the source, 34 to 68 mg/L (2 to 4 grains per gallon), across 3 sampling points, 2020 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
ArsenicThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2025 to Dec. 31, 20250.015 MG/LArchived
ArsenicThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2025 to Sept. 30, 20250.015 MG/LArchived
ArsenicThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2025 to June 30, 20250.015 MG/LArchived
ArsenicThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 31, 2025 to March 31, 20250.014 MG/LArchived
Lead and Copper Rule RevisionsThe required inventory of lead service lines was not completed or submitted on time.EPA: LSL InventoryOct. 17, 2024—Addressed
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 3 monitoring or reporting violations not shown.

What this report can’t tell you

  • Everything else. Arsenic, total trihalomethanes (TTHM), uranium, haloacetic acids (HAA5), fluoride, chromium (total) and nitrate results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Tranquillity Irrigation 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 Feb. 20, 2020 to June 26, 2026.

Testing your own tap

Tranquillity Irrigation 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 Tranquillity Irrigation District serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Dellavalle Laboratory, Inc.

    Fresno, CA · about 26 miles

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

    (559) 233-6129

  • Moore Twining Associates, Inc.

    Fresno, CA · about 28 miles

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

    (559) 268-7021

  • BSK Associates

    Fresno, CA · about 34 miles

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

    (559) 497-2888

All 145 certified labs for California

Sources

PWSID CA1010030. Rebuilt from EPA data on Oct. 18, 2026.

Also in Fresno County

All California utilities

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