Sierra Linda Mutual Water 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
- 200 people
- Connections
- 89
- Water source
- Groundwater
- Based in
- North Fork, CA
- County
- Madera
- Owner
- Private
- Hardness
- Varies by source
The ZIP code it serves
The short answer
2 results are above EPA’s legal limit, and 1 more is above the health goal. The worst: Uranium, above the legal limit. 56 health-based violations since 2016.
What handles itWhat was found
Lead and copper: EPA SDWIS monitoring periods ending 2016 to 2025.
Uranium, arsenic, fluoride, nitrate, chromium (total) and total trihalomethanes (TTHM): California’s own results, samples taken from March 8, 2020 to March 8, 2026, with EPA’s 2012 to 2019 file for earlier years.
Above the legal limit2
Uranium
Comes from the source
277ppb
Highest yearly average, 2020 to 2026
2026 average: 128 ppb
Averaged by year, the highest was 277 ppb, in 2024, about 9.2 times EPA’s legal limit of 30 ppb. Its highest single sample was 998 ppb. In 2026, the latest year on file, its three samples averaged 128 ppb, above the limit. EPA recorded violations for uranium at this utility in 2023, 2024, 2025 and 2026. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 231 ppb, in 2019, and EPA recorded violations in 2014, 2015, 2016, 2017, 2018 and 2019.
What handles it
- NSF/ANSI 58 look for “Uranium”
Arsenic
Comes from the source
22ppb
Highest yearly average, 2020 to 2026
2026 average: 16.3 ppb
Averaged by year, the highest was 22 ppb, in 2022, about twice EPA’s legal limit of 10 ppb. Its highest single sample was 38 ppb. In 2026, the latest year on file, its three samples averaged 16.3 ppb, above the limit. EPA recorded violations for arsenic at this utility in 2020, 2021, 2022, 2023, 2024, 2025 and 2026. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 16.5 ppb, in 2013, and EPA recorded violations in 2012, 2013, 2014, 2015, 2016, 2017, 2018 and 2019.
What handles it
- NSF/ANSI 58 look for “Arsenic (Pentavalent)<=50 ppb Reduction”
- NSF/ANSI 53 look for “Arsenic (Pentavalent)<=50 ppb Reduction”
Above the health goal1
Lead
Comes from pipes, often your own
3.1ppb
90th percentile, 2023 to 2025
In the latest period, 9 in 10 homes sampled were at or below 3.1 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
- NSF/ANSI 53 look for “Lead Reduction”
- NSF/ANSI 58 look for “Lead Reduction”
Below EPA’s limits2
Fluoride
Forms or is added in treatment
0.36ppm
Highest yearly average, 2020 to 2023
Averaged by year, the highest was 0.36 ppm, in 2023, below EPA’s legal limit of 4.0 ppm. Its highest single sample was 0.48 ppm. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.41 ppm, in 2017.
What handles it
- NSF/ANSI 58 look for “Fluoride Reduction”
- NSF/ANSI 53 look for “Fluoride”
Nitrate
Comes from the source
0.83ppm
Highest sample; found in 3 of 18
2025 average: 0.13 ppm
The highest sample, in 2020, was 0.83 ppm, below EPA’s legal limit of 10 ppm. In 2025, the latest year on file, its four samples averaged 0.13 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 0.84 ppm, in 2013.
What handles it
- NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
- NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”
2 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
- Chromium (total)
- Total trihalomethanes (TTHM)
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: Arsenic (Pentavalent)<=50 ppb Reduction, Lead Reduction
For: Arsenic, Lead
Other certifiers’ wording: Arsenic (III) (50 ppb influent level)
- NSF/ANSI 58
Claims: Uranium, Arsenic (Pentavalent)<=50 ppb Reduction, Lead Reduction
For: Uranium, Arsenic, Lead
Other certifiers’ wording: Arsenic (Pentavalent)<=300 ppb Reduction; Arsenic (V) (300 ppb influent level)
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
Countertop reverse osmosis
- IAPMO listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 4, 2026
Certified for: Arsenic, Lead
Aquasana SmartFlow Reverse Osmosis (AQ-SFRO2)
Under-sink reverse osmosis
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 9, 2026
Certified for: Arsenic, Lead
Brondell Capella RC250 Reverse Osmosis System
Under-sink reverse osmosis
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 9, 2026
Certified for: Arsenic, Lead
Brita Tahoe Pitcher with Elite Filter (OB60, OB06)
Pitcher
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 401checked Oct. 13, 2026
- IAPMO listing:NSF/ANSI 53checked Oct. 13, 2026
Certified for: Lead
Hardness
Moderately hard to hard depending on the source, 66 to 150 mg/L (3.9 to 8.8 grains per gallon), across 3 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
| Contaminant or rule | Type | Period | Measured | Status |
|---|---|---|---|---|
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2026 to June 30, 2026 | 0.014 MG/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2026 to June 30, 2026 | 198 PCI/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2026 to March 31, 2026 | 250 PCI/L | Archived |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2026 to March 31, 2026 | 0.019 MG/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2025 to Dec. 31, 2025 | 278 PCI/L | Archived |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2025 to Dec. 31, 2025 | 0.024 MG/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | July 1, 2025 to Sept. 30, 2025 | 308 PCI/L | Archived |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | July 1, 2025 to Sept. 30, 2025 | 0.025 MG/L | Archived |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2025 to June 30, 2025 | 0.024 MG/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2025 to June 30, 2025 | 350 PCI/L | Archived |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2025 to March 31, 2025 | 0.024 MG/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2025 to March 31, 2025 | 423 PCI/L | Archived |
| 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 |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2024 to Dec. 31, 2024 | 0.02 UG/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2024 to Dec. 31, 2024 | 70 PCI/L | Archived |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2024 to June 30, 2024 | 21.1 UG/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2024 to June 30, 2024 | 328 PCI/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2024 to March 31, 2024 | 235 PCI/L | Archived |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2024 to March 31, 2024 | 29 UG/L | Archived |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2023 to Dec. 31, 2023 | 0.03 MG/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2023 to Dec. 31, 2023 | 208 PCI/L | Archived |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | July 1, 2023 to Sept. 30, 2023 | 0.035 MG/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | July 1, 2023 to Sept. 30, 2023 | 185 PCI/L | Archived |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2023 to June 30, 2023 | 0.035 MG/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2023 to June 30, 2023 | 152 PCI/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2023 to March 31, 2023 | 103 PCI/L | Archived |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2023 to March 31, 2023 | 35.3 UG/L | Archived |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2022 to Dec. 31, 2022 | 0.034 MG/L | Archived |
| Arsenic | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | July 1, 2022 to Sept. 30, 2022 | 10.1 UG/L | Archived |
| Arsenic | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | April 1, 2022 to June 30, 2022 | 11 UG/L | Archived |
| Arsenic | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | April 1, 2022 to June 30, 2022 | 34 MG/L | Archived |
| Arsenic | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | Jan. 1, 2022 to March 31, 2022 | 28 UG/L | Archived |
| Arsenic | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | Jan. 1, 2022 to March 31, 2022 | 18 UG/L | Archived |
| Arsenic | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | Oct. 1, 2021 to Dec. 31, 2021 | 0.012 MG/L | Archived |
| Arsenic | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | Oct. 1, 2021 to Dec. 31, 2021 | 0.031 MG/L | Archived |
| Arsenic | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | July 1, 2021 to Sept. 30, 2021 | 0.029 MG/L | Archived |
| Arsenic | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | July 1, 2021 to Sept. 30, 2021 | 0.011 MG/L | Archived |
| Arsenic | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | April 1, 2021 to June 30, 2021 | 0.024 MG/L | Archived |
| Arsenic | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | April 1, 2021 to June 30, 2021 | 0.012 MG/L | Archived |
| Arsenic | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | Jan. 1, 2021 to March 31, 2021 | 0.03 MG/L | Archived |
| Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 1 monitoring or reporting violation not shown. | ||||
What this report can’t tell you
Everything else. Uranium, arsenic, fluoride, nitrate, chromium (total) and total trihalomethanes (TTHM) results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Sierra Linda Mutual Water 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 8, 2020 to March 8, 2026.
Testing your own tap
The 3 labs California certifies closest to the area Sierra Linda Mutual Water Co serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
SGS North America, Inc.
Clovis, CA · about 31 miles
Certified for nitrate, lead and copper, metals, minerals and other inorganics, organic chemicals, disinfection byproducts, PFAS
BSK Associates
Fresno, CA · about 38 miles
Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, organic chemicals, disinfection byproducts, PFAS, radioactivity
Dellavalle Laboratory, Inc.
Fresno, CA · about 40 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 Nov. 30, 2020 to Nov. 27, 2023, read Oct. 10, 2026
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID CA2000506. Rebuilt from EPA data on Oct. 18, 2026.
What to do next
- Read up on the 3 results above a lineWhat each one does to health, where it comes from, and the certification claim that addresses it.Start with Uranium
- Get the utility’s own reportSierra Linda Mutual Water Co 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