R.S. 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
- 35 people
- Connections
- 22
- Water source
- Groundwater
- Based in
- Wofford Heights, CA
- County
- Kern
- Owner
- Private
- Hardness
- Very hard
The ZIP code it serves
The short answer
3 results are above EPA’s legal limit, and 1 more is above the health goal. The worst: Arsenic, above the legal limit. 73 health-based violations since 2016.
What handles itWhat was found
Lead and copper: EPA SDWIS monitoring periods ending 2012 to 2024.
Arsenic, uranium, nitrate, total trihalomethanes (TTHM), fluoride, chromium (total) and haloacetic acids (HAA5): California’s own results, samples taken from Feb. 4, 2020 to May 20, 2026, with EPA’s 2012 to 2019 file for earlier years.
Above the legal limit3
Arsenic
Comes from the source
31.5ppb
Highest yearly average, 2020 to 2026
Averaged by year, the highest was 31.5 ppb, in 2026, about 3.2 times EPA’s legal limit of 10 ppb. Its highest single sample was 53 ppb. That was also the latest year on file. EPA recorded violations for arsenic at this utility in 2020, 2021 and 2023. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 11.4 ppb, in 2012, 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”
Uranium
Comes from the source
45.4ppb
Highest yearly average, 2020 to 2026
2026 average: 29.1 ppb
Averaged by year, the highest was 45.4 ppb, in 2020, above EPA’s legal limit of 30 ppb. Its highest single sample was 47.7 ppb. In 2026, the latest year on file, its two samples averaged 29.1 ppb. EPA recorded violations for uranium at this utility in 2020, 2021, 2022, 2023, 2024 and 2025. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 48.4 ppb, in 2018, and EPA recorded violations in 2016, 2017, 2018 and 2019.
What handles it
- NSF/ANSI 58 look for “Uranium”
Nitrate
Comes from the source
14ppm
Highest sample; found in 27 of 27
2026 average: 9.9 ppm
From 2020 to 2026, 16 samples were above EPA’s legal limit of 10 ppm, the highest 14 ppm in 2020. 16 have no follow-up sample on file within 30 days. In 2026, the latest year on file, its two samples averaged 9.9 ppm. EPA recorded violations for nitrate at this utility in 2020, 2021, 2022, 2023, 2024 and 2025. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 13 ppm, in 2018, and EPA recorded violations in 2013, 2014, 2017, 2018 and 2019.
What handles it
- NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
- NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”
Above the health goal1
Lead
Comes from pipes, often your own
0.6ppb
90th percentile, 2024
In the latest period, 9 in 10 homes sampled were at or below 0.6 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
Total trihalomethanes (TTHM)
Forms or is added in treatment
16ppb
Highest yearly average, 2020 to 2024
Averaged by year, the highest was 16 ppb, in 2024, 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 5.8 ppb, in 2019.
What handles it
- NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
- NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”
Fluoride
Forms or is added in treatment
0.22ppm
Highest yearly average, 2021 to 2024
Averaged by year, the highest was 0.22 ppm, in 2024, below EPA’s legal limit of 4.0 ppm. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.26 ppm, in 2012.
What handles it
- NSF/ANSI 58 look for “Fluoride Reduction”
- NSF/ANSI 53 look for “Fluoride”
2 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
- Chromium (total)
- Haloacetic acids (HAA5)
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, Nitrate/Nitrite (30 ppm challenge), Lead Reduction
For: Arsenic, Nitrate, Lead
Other certifiers’ wording: Arsenic (III) (50 ppb influent level)
- NSF/ANSI 58
Claims: Arsenic (Pentavalent)<=50 ppb Reduction, Uranium, Nitrate/Nitrite Reduction, Lead Reduction
For: Arsenic, Uranium, Nitrate, Lead
Other certifiers’ wording: Arsenic (Pentavalent)<=300 ppb Reduction; Arsenic (V) (300 ppb influent level); Nitrate
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, Nitrate, 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, Nitrate, 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
Culligan 10-Cup Pitcher with ZeroWater Technology (ZEROP10)
Pitcher
- IAPMO listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 401checked Oct. 9, 2026
Certified for: Nitrate, Lead
Hardness
Very hard, 375 mg/L (21.9 grains per gallon), at its one sampling point, 2021 to 2024.
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 |
|---|---|---|---|---|
| Nitrate | 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, 2025 to Dec. 31, 2025 | 13 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 | 23 PCI/L | Archived |
| Nitrate | 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, 2025 to Sept. 30, 2025 | 12 MG/L | Archived |
| Nitrate | 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, 2025 to June 30, 2025 | 13 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 | 24 PCI/L | Archived |
| Nitrate | 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, 2025 to March 31, 2025 | 11 MG/L | Archived |
| Nitrate | 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, 2024 to Dec. 31, 2024 | 12 MG/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 | 24 PCI/L | Archived |
| Nitrate | 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, 2024 to Sept. 30, 2024 | 12 MG/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | July 1, 2024 to Sept. 30, 2024 | 25 PCI/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 | 23 PCI/L | Archived |
| Nitrate | 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, 2024 to March 31, 2024 | 14 MG/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 | 29 PCI/L | Archived |
| Nitrate | 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, 2023 to Dec. 31, 2023 | 13 MG/L | Archived |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2023 to Dec. 31, 2023 | 0.028 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 | 27 PCI/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 | 28 PCI/L | Archived |
| Nitrate | 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, 2023 to June 30, 2023 | 13 MG/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 | 26 PCI/L | Archived |
| Nitrate | 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, 2022 to Dec. 31, 2022 | 12 MG/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2022 to Dec. 31, 2022 | 26 PCI/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | July 1, 2022 to Sept. 30, 2022 | 24 PCI/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2022 to June 30, 2022 | 22 PCI/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2021 to Dec. 31, 2021 | 22 PCI/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | July 1, 2021 to Sept. 30, 2021 | 25 PCI/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2021 to June 30, 2021 | 28 PCI/L | Archived |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2021 to March 31, 2021 | 0.011 MG/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2021 to March 31, 2021 | 31 PCI/L | Archived |
| Nitrate | 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 | 14 MG/L | Archived |
| Nitrate | 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, 2020 to Dec. 31, 2020 | 13 MG/L | Archived |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2020 to Dec. 31, 2020 | 0.011 MG/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2020 to Dec. 31, 2020 | 31 PCI/L | Archived |
| Nitrate | 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, 2020 to Sept. 30, 2020 | 13 MG/L | Archived |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | July 1, 2020 to Sept. 30, 2020 | 0.011 MG/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | July 1, 2020 to Sept. 30, 2020 | 31 PCI/L | Archived |
| Nitrate | 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, 2020 to March 31, 2020 | 14 MG/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2020 to March 31, 2020 | 31 PCI/L | Archived |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2020 to March 31, 2020 | 0.011 MG/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2019 to Dec. 31, 2019 | 30 PCI/L | Archived |
| Arsenic | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2019 to Dec. 31, 2019 | 0.011 MG/L | Archived |
| Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. | ||||
What this report can’t tell you
Everything else. Arsenic, uranium, nitrate, total trihalomethanes (TTHM), fluoride, chromium (total) and haloacetic acids (HAA5) results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. R.S. 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 Feb. 4, 2020 to May 20, 2026.
Testing your own tap
The 3 labs California certifies closest to the area R.S. Mutual Water Company serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
Pace Analytical Services, LLC dba BC Laboratories, Inc.
Bakersfield, CA · about 37 miles
Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, organic chemicals, disinfection byproducts, radioactivity
Zalco Laboratories, Inc.
Bakersfield, CA · about 37 miles
Certified for bacteria, nitrate, metals, minerals and other inorganics, organic chemicals, disinfection byproducts
BSK Associates - Bakersfield Analytical Laboratory
Bakersfield, CA · about 42 miles
Certified for bacteria
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 Aug. 5, 2021 to Aug. 27, 2024, read Oct. 10, 2026
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID CA1500458. Rebuilt from EPA data on Oct. 18, 2026.
What to do next
- Read up on the 4 results above a lineWhat each one does to health, where it comes from, and the certification claim that addresses it.Start with Arsenic
- Get the utility’s own reportR.S. 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
- Compare certified filtersWhat the filters certified for these results cost over five years, cartridges included.Compare five-year costs