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Rancho Pauma Mutual WC

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
899 people
Connections
387
Water source
Groundwater
Based in
Pauma Valley, CA
County
San Diego
Owner
Private
Hardness
Very hard
The ZIP code it serves

92061

The short answer

2 results are above EPA’s legal limit, and 3 more are above the health goal. The worst: Nitrate, above the legal limit. 1 health-based violation since 2016.

What handles it

What was found

Lead and copper: EPA SDWIS monitoring periods ending 1993 to 2022.

Nitrate, uranium, arsenic, total trihalomethanes (TTHM), haloacetic acids (HAA5), fluoride and chromium (total): California’s own results, samples taken from Jan. 7, 2020 to June 9, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the legal limit2

Nitrate

Comes from the source

Above the legal limit

21ppm

Highest sample; found in 97 of 97

2026 average: 3.5 ppm

From 2020 to 2026, three samples were above EPA’s legal limit of 10 ppm, the highest 21 ppm in 2020. Three have no follow-up sample on file within 30 days. In 2026, the latest year on file, its 21 samples averaged 3.5 ppm. EPA recorded a violation for nitrate at this utility in 2026. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 27 ppm, in 2018.

What handles it

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

Copper

Comes from pipes, often your own

Above the action level

1.6ppm

90th percentile, 2022

In the latest period, 9 in 10 homes sampled were at or below 1.6 ppm, above EPA’s action level of 1.3 ppm.

What handles it

Above the health goal3

Uranium

Comes from the source

Above the health goal

4.7ppb

Highest yearly average, 2021 to 2025

Averaged by year, the highest was 4.7 ppb, in 2025: below EPA’s legal limit of 30 ppb, but above its health goal of zero. Its highest single sample was 4.8 ppb. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 6.2 ppb, in 2013.

What handles it

Lead

Comes from pipes, often your own

Above the health goal

1.3ppb

90th percentile, 2026

In the latest period, 9 in 10 homes sampled were at or below 1.3 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

0.86ppb

Highest yearly average, 2020 to 2026

Averaged by year, the highest was 0.86 ppb, in 2026: below EPA’s legal limit of 10 ppb, but above its health goal of zero. Its highest single sample was 2.2 ppb. That was also the latest year on file.

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 limits3

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

24ppb

Highest yearly average, 2020 to 2026

2026: not found

Averaged by year, the highest was 24 ppb, in 2021, below EPA’s legal limit of 80 ppb. In 2026, the latest year on file, it wasn’t found in its one sample. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 28 ppb, in 2017.

What handles it

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

Haloacetic acids (HAA5)

Forms or is added in treatment

Below EPA’s limits

6.3ppb

Highest yearly average, 2020 to 2026

2026: not found

Averaged by year, the highest was 6.3 ppb, in 2021, below EPA’s legal limit of 60 ppb. In 2026, the latest year on file, it wasn’t found in its one sample. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 8.7 ppb, in 2017.

What handles it

No certification claim covers this compound yet.

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.21ppm

Highest yearly average, 2020 to 2026

2026 average: 0.16 ppm

Averaged by year, the highest was 0.21 ppm, in 2022, below EPA’s legal limit of 4.0 ppm. Its highest single sample was 0.25 ppm. In 2026, the latest year on file, its five samples averaged 0.16 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.21 ppm, in 2017.

What handles it

One compound tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Chromium (total)

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

    For: Nitrate, Copper, Lead, Arsenic

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

  • NSF/ANSI 58

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

    For: Nitrate, Copper, Uranium, Lead, Arsenic

    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, typically 355 mg/L (20.8 grains per gallon), across 7 sampling points, 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 20.8 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, AverageApril 1, 2026 to June 30, 202610.5 MG/LArchived
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 1 monitoring or reporting violation not shown.

What this report can’t tell you

  • Everything else. Nitrate, uranium, arsenic, total trihalomethanes (TTHM), haloacetic acids (HAA5), fluoride and chromium (total) results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Rancho Pauma Mutual WC’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. 7, 2020 to June 9, 2026.

Testing your own tap

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

  • Applied Industrial Microbiology, Inc.

    Vista, CA · about 21 miles

    Certified for bacteria, nitrate

    (760) 295-0430

  • Alpha Analytical Laboratories, Inc. - San Diego

    Vista, CA · about 22 miles

    Certified for bacteria, nitrate, minerals and other inorganics

    (760) 536-3352

  • EMSL Analytical, Inc.

    San Diego, CA · about 35 miles

    Certified for bacteria

    (800) 220-3675

All 145 certified labs for California

Sources

PWSID CA3710012. Rebuilt from EPA data on Oct. 18, 2026.

Also in San Diego County

All California utilities

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