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Rancho Carrillo MWC

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
210 people
Connections
75
Water source
Groundwater
Based in
Rancho Mission Viejo, CA
County
Riverside
Owner
Private
Hardness
Varies by source
The ZIP code it serves

92562

The short answer

4 results are above the health goal. The worst: Nitrate, above the health goal. 3 health-based violations since 2016.

What handles it

What was found

Lead and copper: EPA SDWIS monitoring periods ending 2012 to 2023.

Nitrate, arsenic, uranium, fluoride and chromium (total): California’s own results, samples taken from Feb. 26, 2020 to July 9, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the health goal4

Nitrate

Comes from the source

Above the health goal

12.7ppm

Highest sample; found in 56 of 56

2026 average: 6.5 ppm

In 2023, two samples were above EPA’s legal limit of 10 ppm, the highest 12.7 ppm. Two have no follow-up sample on file within 30 days. 10 ppm is also EPA’s health goal. In 2026, the latest year on file, its eight samples averaged 6.5 ppm. EPA recorded no violation for nitrate at this utility since 2020. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 12.2 ppm, in 2017, and EPA recorded a violation in 2017.

What handles it

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

Lead

Comes from pipes, often your own

Above the health goal

5.0ppb

90th percentile, 2021 to 2023

In the latest period, 9 in 10 homes sampled were at or below 5.0 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

Arsenic

Comes from the source

Above the health goal

1.7ppb

Highest yearly average, 2023 to 2026

Averaged by year, the highest was 1.7 ppb, in 2026: below EPA’s legal limit of 10 ppb, but above its health goal of zero. Its highest single sample was 5.6 ppb. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 1.3 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”

Uranium

Comes from the source

Above the health goal

0.79ppb

Highest yearly average, 2023

Averaged by year, the highest was 0.79 ppb, in 2023: below EPA’s legal limit of 30 ppb, but above its health goal of zero. Its highest single sample was 2.4 ppb. That is the only year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 1.4 ppb, in 2018.

What handles it

Below EPA’s limits2

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.069ppm

Highest yearly average, 2023 to 2026

Averaged by year, the highest was 0.069 ppm, in 2026, below EPA’s legal limit of 4.0 ppm. Its highest single sample was 0.1 ppm. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.24 ppm, in 2013.

What handles it

Chromium (total)

Comes from the source

Below EPA’s limits

0.6ppb

Highest yearly average, 2023 to 2026

2026: not found

Averaged by year, the highest was 0.6 ppb, in 2023, below EPA’s legal limit of 100 ppb. Its highest single sample was 4.2 ppb. In 2026, the latest year on file, it wasn’t found in any of its five samples. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 19.3 ppb, in 2013.

What handles it

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), Lead Reduction, Arsenic (Pentavalent)<=50 ppb Reduction

    For: Nitrate, Lead, Arsenic

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

  • NSF/ANSI 58

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

    For: Nitrate, Lead, Arsenic, Uranium

    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

Hard to very hard depending on the source, 140 to 423 mg/L (8.2 to 24.7 grains per gallon), across 7 sampling points, 2023 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
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleJuly 1, 2017 to Sept. 30, 201711.1 MG/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleApril 1, 2017 to June 30, 201711.7 MG/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleJan. 1, 2017 to March 31, 201711.7 MG/LResolved
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. Nitrate, arsenic, uranium, fluoride and chromium (total) results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Rancho Carrillo MWC’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. 26, 2020 to July 9, 2026.

Testing your own tap

Rancho Carrillo MWC’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 Rancho Carrillo MWC serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Sierra Analytical Labs, Inc.

    Laguna Hills, CA · about 19 miles

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

    (949) 348-9389

  • Babcock Laboratories, Inc.

    Riverside, CA · about 27 miles

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

    (951) 653-3351

  • Applied Industrial Microbiology, Inc.

    Vista, CA · about 28 miles

    Certified for bacteria, nitrate

    (760) 295-0430

All 145 certified labs for California

Sources

PWSID CA3301535. Rebuilt from EPA data on Oct. 18, 2026.

Also in Riverside County

All California utilities

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