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Rancho Santa Teresa Mw Co.

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
102 people
Connections
38
Water source
Groundwater
Based in
Ramona, CA
County
San Diego
Owner
Private
Hardness
Very hard
The ZIP code it serves

92065

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: Nitrate, above the legal limit. 20 health-based violations since 2016.

What handles it

What was found

Lead and copper: EPA SDWIS monitoring periods ending 2018 to 2025.

Nitrate, uranium, fluoride, arsenic and chromium (total): California’s own results, samples taken from March 9, 2020 to June 17, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the legal limit1

Nitrate

Comes from the source

Above the legal limit

13ppm

Highest sample; found in 102 of 102

2026 average: 4.8 ppm

From 2023 to 2024, 22 samples were above EPA’s legal limit of 10 ppm, the highest 13 ppm in 2023. The next sample at the same point, within 30 days, kept the average above the limit for 19; two came back under and one has no follow-up sample on file within 30 days. In 2026, the latest year on file, its nine samples averaged 4.8 ppm. EPA recorded violations for nitrate at this utility in 2023 and 2024. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 17.4 ppm, in 2016, and EPA recorded a violation in 2018.

What handles it

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

Above the limit’s level, no violation recorded1

Uranium

Comes from the source

Above the limit’s level, no violation

96.9ppb

Highest yearly average, 2020 to 2026

2026 average: 33.7 ppb

Averaged by year, the highest was 96.9 ppb, in 2020, about 3.2 times EPA’s legal limit of 30 ppb. Its highest single sample was 298 ppb. In 2026, the latest year on file, its 16 samples averaged 33.7 ppb, above the limit. EPA judges this limit on running averages at each sampling point, and recorded no violation for uranium 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 103 ppb, in 2019, and EPA recorded violations in 2014, 2015, 2016, 2017, 2018 and 2019.

What handles it

Above the health goal1

Lead

Comes from pipes, often your own

Above the health goal

3.7ppb

90th percentile, 2025

In the latest period, 9 in 10 homes sampled were at or below 3.7 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

Below EPA’s limits1

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.14ppm

Highest yearly average, 2020 to 2023

Averaged by year, the highest was 0.14 ppm, in 2023, below EPA’s legal limit of 4.0 ppm. Its highest single sample was 0.15 ppm. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.14 ppm, in 2014.

What handles it

2 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Arsenic
  • 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), Lead Reduction

    For: Nitrate, Lead

  • NSF/ANSI 58

    Claims: Nitrate/Nitrite Reduction, Uranium, Lead Reduction

    For: Nitrate, Uranium, Lead

    Other certifiers’ wording: Nitrate

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 268 mg/L (15.6 grains per gallon), across 2 sampling points, 2020 to 2023.

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 15.6 grains per gallon, 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 SampleOct. 1, 2024 to Dec. 31, 202411 MG/LArchived
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleOct. 1, 2023 to Dec. 31, 202313 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, 2023 to Sept. 30, 202311 MG/LArchived
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2019 to June 30, 2019130 PCI/LResolved
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2019 to June 30, 201959 PCI/LResolved
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2019 to March 31, 2019120 PCI/LResolved
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2019 to March 31, 201992 PCI/LResolved
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2018 to Dec. 31, 201836 PCI/LResolved
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2018 to Dec. 31, 2018110 PCI/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleJuly 1, 2018 to Sept. 30, 201810.5 MG/LResolved
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2018 to June 30, 201820.3 PCI/LResolved
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2018 to March 31, 201820.5 PCI/LResolved
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2017 to Dec. 31, 201720.7 PCI/LResolved
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2017 to Sept. 30, 201720.8 PCI/LResolved
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2017 to June 30, 201767.3 PCI/LResolved
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2017 to March 31, 201751.3 PCI/LResolved
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2016 to Dec. 31, 201647 PCI/LResolved
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2016 to Sept. 30, 201646.8 PCI/LResolved
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2016 to June 30, 201645.5 PCI/LResolved
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2016 to March 31, 201641.9 PCI/LResolved
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 48 monitoring or reporting violations not shown.

What this report can’t tell you

  • Everything else. Nitrate, uranium, fluoride, arsenic and chromium (total) results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Rancho Santa Teresa Mw Co.’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 March 9, 2020 to June 17, 2026.

Testing your own tap

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

  • EMSL Analytical, Inc.

    San Diego, CA · about 23 miles

    Certified for bacteria

    (800) 220-3675

  • Analytical Environmental Lab, LLC

    San Diego, CA · about 23 miles

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

    (619) 871-8505

  • Applied Industrial Microbiology, Inc.

    Vista, CA · about 23 miles

    Certified for bacteria, nitrate

    (760) 295-0430

All 145 certified labs for California

Sources

PWSID CA3700918. Rebuilt from EPA data on Oct. 18, 2026.

Towns it serves

Also in San Diego County

All California utilities

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