NPS - Grant Grove
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
- 2,950 people
- Connections
- 100
- Water source
- Groundwater
- Based in
- Three Rivers, CA
- County
- Fresno
- Owner
- Federal government
- Hardness
- Soft
The ZIP code it serves
The short answer
1 result is above the health goal. The worst: Uranium, above the health goal. No health-based violations on file since 2016.
What handles itWhat was found
Copper: EPA’s file records a utility’s copper only when it exceeds the action level. The last here was 1.9 ppm, for the period ending June 30, 2019. None since is on file, so it is not counted as a current finding.
Uranium, haloacetic acids (HAA5), total trihalomethanes (TTHM), nitrate, arsenic, chromium (total) and fluoride: California’s own results, samples taken from July 1, 2020 to Jan. 7, 2026, with EPA’s 2012 to 2019 file for earlier years.
Above the health goal1
Uranium
Comes from the source
4.7ppb
Highest yearly average, 2022
Averaged by year, the highest was 4.7 ppb, in 2022: below EPA’s legal limit of 30 ppb, but above its health goal of zero. That is the only year on file.
What handles it
- NSF/ANSI 58 look for “Uranium”
Below EPA’s limits3
Haloacetic acids (HAA5)
Forms or is added in treatment
14ppb
Highest yearly average, 2022 to 2025
2025, one sample: 13 ppb
Averaged by year, the highest was 14 ppb, in 2022, below EPA’s legal limit of 60 ppb. In 2025, the latest year on file, its one sample was 13 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 25 ppb, in 2019.
What handles it
No certification claim covers this compound yet.
Total trihalomethanes (TTHM)
Forms or is added in treatment
15ppb
Highest yearly average, 2022 to 2025
Averaged by year, the highest was 15 ppb, in 2025, below EPA’s legal limit of 80 ppb. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 12 ppb, in 2019.
What handles it
- NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
- NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”
Nitrate
Comes from the source
0.7ppm
Highest sample; found in 2 of 14
2026: not found
The highest sample, in 2021, was 0.7 ppm, below EPA’s legal limit of 10 ppm. In 2026, the latest year on file, it wasn’t found in any of its two samples. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 0.5 ppm, in 2018.
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
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 58
Claim: Uranium
For: Uranium
At the tap, or for the whole house?
These come with the water itself, so a whole-house system certified for the same claims treats every tap and shower. A filter at the tap treats drinking water for much less. How whole-house systems compare.
Filters with those claims on a certifier’s listing
None of the filters TapBuff has checked so far carry these claims. Search the certifier listings for the claim above.
Compare five-year costsHardness
Soft, typically 11 mg/L (0.7 grains per gallon), across 2 sampling points, 2022 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
No health-based violations on file with EPA since 2016. There are 3 monitoring or reporting violations: a sample missed, late or not reported.
What this report can’t tell you
Everything else. Uranium, haloacetic acids (HAA5), total trihalomethanes (TTHM), nitrate, arsenic, chromium (total) and fluoride results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. NPS - Grant Grove’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 1, 2020 to Jan. 7, 2026.
Testing your own tap
The 3 labs California certifies closest to the area NPS - Grant Grove serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
Inyo County Water Lab
Independence, CA · about 25 miles
Certified for bacteria
Fruit Growers Laboratory, Inc.
Visalia, CA · about 53 miles
Certified for bacteria
SGS North America, Inc.
Clovis, CA · about 56 miles
Certified for nitrate, lead and copper, metals, minerals and other inorganics, organic chemicals, disinfection byproducts, PFAS
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 Feb. 2, 2022 to Jan. 15, 2025, read Oct. 10, 2026
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID CA1010501. Rebuilt from EPA data on Oct. 18, 2026.
What to do next
- Read up on UraniumWhat each one does to health, where it comes from, and the certification claim that addresses it.About Uranium
- Get the utility’s own reportNPS - Grant Grove 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
- Compare certified filtersWhat the filters certified for these results cost over five years, cartridges included.Compare five-year costs