R Ranch at the Lake
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
- 20 people
- Connections
- 16
- Water source
- Groundwater
- Based in
- Napa, CA
- County
- Napa
- Owner
- Private
- Hardness
- Very hard
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. 1 health-based violation since 2016.
What was found
Total trihalomethanes (TTHM), haloacetic acids (HAA5), nitrate, arsenic, chromium (total) and fluoride: California’s own results, samples taken from July 7, 2020 to Nov. 4, 2025, with EPA’s 2012 to 2019 file for earlier years.
Below EPA’s limits3
Total trihalomethanes (TTHM)
Forms or is added in treatment
39ppb
Highest yearly average, 2020 to 2025
2025: not found
Averaged by year, the highest was 39 ppb, in 2022, below EPA’s legal limit of 80 ppb. In 2025, the latest year on file, it wasn’t found in its one sample.
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
17ppb
Highest yearly average, 2020 to 2025
2025: not found
Averaged by year, the highest was 17 ppb, in 2022, below EPA’s legal limit of 60 ppb. In 2025, the latest year on file, it wasn’t found in its one sample.
What handles it
No certification claim covers this compound yet.
Nitrate
Comes from the source
0.55ppm
Highest sample; found in 8 of 15
2025 average: 0.13 ppm
The highest sample, in 2022, was 0.55 ppm, below EPA’s legal limit of 10 ppm. In 2025, the latest year on file, its three samples averaged 0.13 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 0.52 ppm, in 2014.
What handles it
- NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
- NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”
4 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
- Arsenic
- Chromium (total)
- Fluoride
- Lead
Hardness
Very hard, typically 389 mg/L (22.7 grains per gallon), across 3 sampling points, 2019 to 2025.
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
| Contaminant or rule | Type | Period | Measured | Status |
|---|---|---|---|---|
| Lead and Copper Rule Revisions | The required inventory of lead service lines was not completed or submitted on time.EPA: LSL Inventory | Oct. 17, 2024 | — | Unaddressed |
| Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 5 monitoring or reporting violations not shown. | ||||
What this report can’t tell you
Everything else. Total trihalomethanes (TTHM), haloacetic acids (HAA5), nitrate, arsenic, chromium (total) and fluoride results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. R Ranch at the Lake’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 July 7, 2020 to Nov. 4, 2025.
Testing your own tap
The 3 labs California certifies closest to the area R Ranch at the Lake serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
Caltest Analytical Laboratory
Napa, CA · about 15 miles
Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, organic chemicals, disinfection byproducts
Napa-Solano-Yolo-Marin Public Health Laboratory
Fairfield, CA · about 17 miles
Certified for bacteria
Brelje and Race Laboratories, Inc.
Santa Rosa, CA · about 25 miles
Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, organic chemicals, disinfection byproducts
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 July 24, 2019 to Nov. 4, 2025, read Oct. 10, 2026
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID CA2800593. 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 reportR Ranch at the Lake 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