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Del Oro Water Co - Metropolitan 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
96 people
Connections
29
Water source
Groundwater
Based in
Chico, CA
County
Fresno
Owner
Private
Hardness
Very hard
The ZIP code it serves

93722

The short answer

1 result is above EPA’s legal limit, and 3 more are above the health goal. The worst: Nitrate, above the legal limit. 9 health-based violations since 2016.

What handles it

What was found

Lead and copper: EPA SDWIS monitoring periods ending 2004 to 2025.

Nitrate, uranium, arsenic, chromium (total), fluoride and total trihalomethanes (TTHM): California’s own results, samples taken from Feb. 10, 2020 to June 2, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the legal limit1

Nitrate

Comes from the source

Above the legal limit

12ppm

Highest sample; found in 27 of 27

2026 average: 11 ppm

From 2020 to 2026, 17 samples were above EPA’s legal limit of 10 ppm, the highest 12 ppm in 2020. The next sample at the same point, within 30 days, kept the average above the limit for one; 16 have no follow-up sample on file within 30 days. In 2026, the latest year on file, its two samples averaged 11 ppm, above the limit. EPA recorded violations for nitrate at this utility in 2020 and 2021. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 12 ppm, in 2019, and EPA recorded a violation in 2019.

What handles it

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

Above the health goal3

Uranium

Comes from the source

Above the health goal

29.7ppb

Highest yearly average, 2022 to 2025

Averaged by year, the highest was 29.7 ppb, in 2025: below EPA’s legal limit of 30 ppb, but above its health goal of zero. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 26.8 ppb, in 2019.

What handles it

Arsenic

Comes from the source

Above the health goal

5.0ppb

Highest yearly average, 2020 to 2023

2023, one sample: 2.0 ppb

Averaged by year, the highest was 5.0 ppb, in 2020: below EPA’s legal limit of 10 ppb, but above its health goal of zero. In 2023, the latest year on file, its one sample was 2.0 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 2.7 ppb, in 2017.

What handles it

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

Lead

Comes from pipes, often your own

Above the health goal

1.6ppb

90th percentile, 2023 to 2025

In the latest period, 9 in 10 homes sampled were at or below 1.6 ppb, below EPA’s action level of 15 ppb. The action level drops to 10 ppb on Nov. 1, 2027. EPA’s health goal for lead is zero.

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)
  • Fluoride
  • Total trihalomethanes (TTHM)

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: Nitrate/Nitrite (30 ppm challenge), Arsenic (Pentavalent)<=50 ppb Reduction, Lead Reduction

    For: Nitrate, Arsenic, Lead

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

  • NSF/ANSI 58

    Claims: Nitrate/Nitrite Reduction, Uranium, Arsenic (Pentavalent)<=50 ppb Reduction, Lead Reduction

    For: Nitrate, Uranium, Arsenic, Lead

    Other certifiers’ wording: Nitrate; Arsenic (Pentavalent)<=300 ppb Reduction; Arsenic (V) (300 ppb influent level)

At the tap, or for the whole house?

Lead and copper usually come from pipes and fixtures inside or near your home. A whole-house system sits where water enters, so it cannot catch what your own plumbing adds after it. For those, the filter that counts is the one at the tap. 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

The best water filters for lead, ranked

Hardness

Very hard, 258 mg/L (15.1 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 15.1 grains per gallon, salt includedSoftener or salt-free conditioner?California water hardness, utility by utility

Violations since 2016

Contaminant or ruleTypePeriodMeasuredStatus
NitrateThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2021 to Dec. 31, 202110.6 MG/LArchived
NitrateThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2021 to Sept. 30, 202110.9 MG/LArchived
NitrateThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2021 to June 30, 202112 MG/LArchived
NitrateThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2021 to March 31, 202111.3 MG/LArchived
NitrateThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2020 to Dec. 31, 202011 MG/LArchived
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleJuly 1, 2020 to Sept. 30, 202011 MG/LArchived
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleApril 1, 2020 to June 30, 202010.4 MG/LArchived
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleJan. 1, 2020 to March 31, 202010.7 MG/LArchived
NitrateThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageNov. 1, 2019 to Nov. 30, 201911.3 MG/LArchived
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. Nitrate, uranium, arsenic, chromium (total), fluoride and total trihalomethanes (TTHM) results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Del Oro Water Co - Metropolitan 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. 10, 2020 to June 2, 2026.

Testing your own tap

Del Oro Water Co - Metropolitan 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 Del Oro Water Co - Metropolitan 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 4 miles

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

    (559) 233-6129

  • Moore Twining Associates, Inc.

    Fresno, CA · about 7 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 12 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 CA1000057. Rebuilt from EPA data on Oct. 18, 2026.

Also in Fresno County

All California utilities

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