Oakmont Water System
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
- 61 people
- Connections
- 26
- Water source
- Surface water bought from another system
- Based in
- Stockton, CA
- County
- Santa Clara
- Owner
- Private
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
Lead and copper: copper at 605 mg/L (2004) is left out of this report: more than 20 times the action level, it looks like µg/L entered as mg/L.
Haloacetic acids (HAA5) and total trihalomethanes (TTHM): California’s own results, samples taken from Jan. 20, 2020 to July 21, 2025, with EPA’s 2012 to 2019 file for earlier years.
Below EPA’s limits2
Haloacetic acids (HAA5)
Forms or is added in treatment
31ppb
Highest yearly average, 2020 to 2025
2025, one sample: 24 ppb
Averaged by year, the highest was 31 ppb, in 2022, below EPA’s legal limit of 60 ppb. In 2025, the latest year on file, its one sample was 24 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 19 ppb, in 2018.
What handles it
No certification claim covers this compound yet.
Total trihalomethanes (TTHM)
Forms or is added in treatment
36ppb
Highest yearly average, 2020 to 2025
2025, one sample: 22 ppb
Averaged by year, the highest was 36 ppb, in 2022, below EPA’s legal limit of 80 ppb. In 2025, the latest year on file, its one sample was 22 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 69 ppb, in 2016.
What handles it
- NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
- NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”
One compound tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
- Lead
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. Haloacetic acids (HAA5) and total trihalomethanes (TTHM) results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Oakmont Water System’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. 20, 2020 to July 21, 2025.
Testing your own tap
The 3 labs California certifies closest to the area Oakmont Water System serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
Santa Cruz County - Health Services Agency - Environmental Health
Santa Cruz, CA · about 12 miles
Certified for bacteria
Torrent Laboratory, Inc
Milpitas, CA · about 18 miles
Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, organic chemicals, disinfection byproducts, PFAS
Bracewell Engineering, Inc.
Morgan Hill, CA · about 19 miles
Certified for bacteria, nitrate, minerals and other inorganics
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
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID CA4300526. 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 reportOakmont Water System 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