Madison Service Dist
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
- 876 people
- Connections
- 149
- Water source
- Groundwater
- Based in
- Madison, CA
- County
- Yolo
- Owner
- Local government
- Hardness
- Varies by source
The ZIP code it serves
The short answer
1 result is above the health goal. The worst: Uranium, above the health goal. 1 health-based violation since 2016.
What handles itWhat was found
Uranium, nitrate, chromium (total), fluoride, total trihalomethanes (TTHM), arsenic and haloacetic acids (HAA5): California’s own results, samples taken from Aug. 28, 2020 to June 30, 2026, with EPA’s 2012 to 2019 file for earlier years.
Above the health goal1
Uranium
Comes from the source
1.7ppb
Highest yearly average, 2022 to 2023
2023: not found
Averaged by year, the highest was 1.7 ppb, in 2022: below EPA’s legal limit of 30 ppb, but above its health goal of zero. In 2023, the latest year on file, it wasn’t found in its one sample. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 2.1 ppb, in 2013.
What handles it
- NSF/ANSI 58 look for “Uranium”
Below EPA’s limits4
Nitrate
Comes from the source
10ppm
Highest sample; found in 17 of 19
2026 average: 5.7 ppm
The highest sample, in 2025, was 10 ppm, below EPA’s legal limit of 10 ppm. In 2026, the latest year on file, its five samples averaged 5.7 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 7.4 ppm, in 2019.
What handles it
- NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
- NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”
Chromium (total)
Comes from the source
11ppb
Highest yearly average, 2022 to 2026
2026 average: 6.0 ppb
Averaged by year, the highest was 11 ppb, in 2022, below EPA’s legal limit of 100 ppb. Its highest single sample was 12 ppb. In 2026, the latest year on file, its two samples averaged 6.0 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 20 ppb, in 2013.
What handles it
- NSF/ANSI 58 look for “Chromium (Hexavalent) Reduction”
- NSF/ANSI 53 look for “Chromium Reduction”
Fluoride
Forms or is added in treatment
0.18ppm
Highest yearly average, 2022 to 2026
2026 average: 0.055 ppm
Averaged by year, the highest was 0.18 ppm, in 2022, below EPA’s legal limit of 4.0 ppm. In 2026, the latest year on file, its two samples averaged 0.055 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.06 ppm, in 2018.
What handles it
- NSF/ANSI 58 look for “Fluoride Reduction”
- NSF/ANSI 53 look for “Fluoride”
Total trihalomethanes (TTHM)
Forms or is added in treatment
0.57ppb
Highest yearly average, 2022 to 2026
Averaged by year, the highest was 0.57 ppb, in 2026, below EPA’s legal limit of 80 ppb. Its highest single sample was 1.7 ppb. That was also the latest year on file.
What handles it
- NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
- NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”
3 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
- Arsenic
- Haloacetic acids (HAA5)
- 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
Hard to very hard depending on the source, 150 to 320 mg/L (8.8 to 18.7 grains per gallon), across 2 sampling points, 2023 to 2026.
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. 138 monitoring or reporting violations not shown. | ||||
What this report can’t tell you
Everything else. Uranium, nitrate, chromium (total), fluoride, total trihalomethanes (TTHM), arsenic and haloacetic acids (HAA5) results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Madison Service Dist’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 Aug. 28, 2020 to June 30, 2026.
Testing your own tap
The 3 labs California certifies closest to the area Madison Service Dist serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
Eurofins Sacramento Service Center
West Sacramento, CA · about 23 miles
Certified for bacteria, nitrate, minerals and other inorganics
Eurofins Sacramento
West Sacramento, CA · about 23 miles
Certified for minerals and other inorganics, organic chemicals, PFAS
Bend Genetics LLC
Sacramento, CA · about 32 miles
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 Sept. 15, 2023 to March 30, 2026, read Oct. 10, 2026
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID CA5700571. 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 reportMadison Service Dist 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