North Peak Mutual Water Company
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
- 294 people
- Connections
- 90
- Water source
- Groundwater
- Based in
- Julian, CA
- County
- San Diego
- Owner
- Private
- Hardness
- Varies by source
The ZIP code it serves
The short answer
Nothing in EPA’s and California’s records for this utility is above a health goal. That covers nitrate, arsenic and other regulated chemicals, plus lead and copper, not everything. No health-based violations on file since 2016.
What was found
Nitrate, fluoride, arsenic, chromium (total), total trihalomethanes (TTHM) and uranium: California’s own results, samples taken from Jan. 14, 2020 to March 17, 2025, with EPA’s 2012 to 2019 file for earlier years.
Below EPA’s limits2
Nitrate
Comes from the source
1.3ppm
Highest sample; found in 9 of 16
2025 average: 0.45 ppm
The highest sample, in 2024, was 1.3 ppm, below EPA’s legal limit of 10 ppm. In 2025, the latest year on file, its two samples averaged 0.45 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 0.77 ppm, in 2013.
What handles it
- NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
- NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”
Fluoride
Forms or is added in treatment
0.061ppm
Highest yearly average, 2020 to 2024
2024: not found
Averaged by year, the highest was 0.061 ppm, in 2020, below EPA’s legal limit of 4.0 ppm. Its highest single sample was 0.12 ppm. In 2024, 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 0.11 ppm, in 2017.
What handles it
- NSF/ANSI 58 look for “Fluoride Reduction”
- NSF/ANSI 53 look for “Fluoride”
5 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
- Arsenic
- Chromium (total)
- Lead
- Total trihalomethanes (TTHM)
- Uranium
Hardness
Hard to very hard depending on the source, 179 to 191 mg/L (10.5 to 11.1 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.
Violations since 2016
No health-based violations on file with EPA since 2016. There is 1 monitoring or reporting violation: a sample missed, late or not reported.
What this report can’t tell you
Everything else. Nitrate, fluoride, arsenic, chromium (total), total trihalomethanes (TTHM) and uranium results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. North Peak Mutual Water Company’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. 14, 2020 to March 17, 2025.
Testing your own tap
The 3 labs California certifies closest to the area North Peak Mutual Water Company 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 40 miles
Certified for bacteria
Analytical Environmental Lab, LLC
San Diego, CA · about 40 miles
Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, disinfection byproducts
Environmental Laboratory Network, Inc.
San Diego, CA · about 41 miles
Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, radioactivity
Sources
- EPA UCMR 5 occurrence data, file of Oct. 15, 2026
- EPA SDWA bulk download (SDWIS federal data), 2026 Q3
- California State Water Resources Control Board, Division of Drinking Water, results from Jan. 1, 2020 to July 17, 2026, read Oct. 8, 2026
- EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, file of Feb. 5, 2024
- Certified labs: California State Water Resources Control Board, ELAP accredited laboratories and their fields of accreditation, read Oct. 17, 2026; distances from the Census 2020 ZIP code tabulation area gazetteer
- Hardness: California State Water Resources Control Board, Division of Drinking Water, results from March 23, 2020 to March 27, 2023, read Oct. 10, 2026
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID CA3701747. Rebuilt from EPA data on Oct. 18, 2026.
What to do next
- Nothing here is above a health goalIn EPA’s and California’s records for this utility. They don’t cover everything, which is why the next step matters.Every contaminant TapBuff tracks
- Get the utility’s own reportNorth Peak Mutual Water Company must send you a water quality report every year. It covers contaminants this page does not show.How to read it
- Test your own tap for leadYour service line, solder and fixtures decide the lead at your faucet, not the utility’s average.Lead in your water: what to do
- Decide if you want a filter at allA filter for taste or chlorine is a preference, not a need. The standards say what each kind can do.NSF/ANSI standards, decoded