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City of Stockton water quality report, rewritten

Serves
191,302
Connections
51,522
Water source
Surface water
Based in
Stockton, CA
County
San Joaquin
Owner
Local government
The 9 ZIP codes it serves

95205, 95206, 95207, 95209, 95210, 95212, 95215, 95219, 95231

PWSID CA39100122026 edition · EPA data

Read this first

  • PFOS (above the health goal) was found in three of 38 samples, highest 28 ppt. Above the 4.0 ppt legal limit in at least one sample. Compliance is judged on a running annual average, not one sample.
  • PFOA (above the health goal) was found in one of 38 samples, highest 6.7 ppt. Above the 4.0 ppt legal limit in at least one sample. Compliance is judged on a running annual average, not one sample.

3 health-based violations since 2016. Details are below.

What handles it

What was found

Highlighted: above the health goal, or EPA’s health benchmark where there is no goal. Circled: above the legal limit in at least one sample, or the action level. Every scale puts that line at its middle.

PFOS (above the health goal)

Comes from the source

28 (above the legal limit in at least one sample)ppt

Highest of 38 samples; found in three

Above the 4.0 ppt legal limit in at least one sample. Compliance is judged on a running annual average, not one sample.

What handles it

  • NSF/ANSI 53Look for: PFOS ReductionSame claim, other certifiers’ wording: Total PFAS Reduction; Perfluorooctane Sulfonate (PFOS)
  • NSF/ANSI 58Look for: Perfluorooctane Sulfonate (PFOS)

NSF’s PFAS claims are tested to below 20 ppt. EPA’s limit is 4.0 ppt, and EPA says no certification yet shows a filter reaching its levels.

EPA UCMR 5, samples taken from Feb. 28, 2023 to Dec. 2, 2025. Each blue tick is one sample where it was found.

PFOA (above the health goal)

Comes from the source

6.7 (above the legal limit in at least one sample)ppt

Highest of 38 samples; found in one

Above the 4.0 ppt legal limit in at least one sample. Compliance is judged on a running annual average, not one sample.

What handles it

  • NSF/ANSI 53Look for: PFOA ReductionSame claim, other certifiers’ wording: Total PFAS Reduction; Perfluorooctanoic Acid (PFOA)
  • NSF/ANSI 58Look for: Perfluorooctanoic Acid (PFOA)

NSF’s PFAS claims are tested to below 20 ppt. EPA’s limit is 4.0 ppt, and EPA says no certification yet shows a filter reaching its levels.

EPA UCMR 5, samples taken on Dec. 2, 2025. Each blue tick is one sample where it was found.

PFBS

Comes from the source

6.2ppt

Highest of 38 samples; found in one

Below EPA’s hazard index benchmark of 2,000 ppt. PFBS has no legal limit or health goal of its own.

What handles it

EPA UCMR 5, samples taken on Dec. 2, 2025. Each blue tick is one sample where it was found.

Tested and not found

Below EPA’s minimum reporting level in every sample taken from Feb. 28, 2023 to Dec. 2, 2025. Not found means not measured above that level, which is not the same as zero.

All 28 compounds tested and not found
  • 11Cl-PF3OUdS
  • 4:2 FTS
  • 6:2 FTS
  • 8:2 FTS
  • 9Cl-PF3ONS
  • ADONA
  • HFPO-DA (GenX)
  • Lead
  • Lithium
  • NEtFOSAA
  • NFDHA
  • NMeFOSAA
  • PFBA
  • PFDA
  • PFDoA
  • PFEESA
  • PFHpA
  • PFHpS
  • PFHxA
  • PFHxS
  • PFMBA
  • PFMPA
  • PFNA
  • PFPeA
  • PFPeS
  • PFTA
  • PFTrDA
  • PFUnA

Violations since 2016

Contaminant or ruleTypePeriodMeasuredStatus
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2023 to June 30, 20230.083 MG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2023 to March 31, 20230.081 MG/LResolved
Surface Water Treatment RuleRequired treatment for surface water or groundwater was not met.EPA: Treatment Technique (SWTR and GWR)March 1, 2016 to March 31, 2016—Resolved
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 2 monitoring or reporting violations not shown.

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: PFOS Reduction, PFOA Reduction

    For: PFOS, PFOA

  • NSF/ANSI 58

    Claims: Perfluorooctane Sulfonate (PFOS), Perfluorooctanoic Acid (PFOA)

    For: PFOS, PFOA

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.

Compare five-year costs

Filters with those claims on a certifier’s listing

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

What this report cannot tell you

  • Levels of everything else. Federal bulk data carries results for PFAS, lithium, lead and copper, and violations for the rest. Nitrate, arsenic, disinfection byproducts and other levels are in City of Stockton’s own annual report, which it must send you every year.
  • 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.
  • Anything after the latest data. SDWIS data is from 2026 Q2; UCMR 5 samples are from Feb. 28, 2023 to Dec. 2, 2025.

What to do next

  1. Read up on the 2 marked results

    What each one does to health, where it comes from, and the certification claim that addresses it.

    Start with PFOS

  2. Get the utility’s own report

    City of Stockton must send you a water quality report every year. It lists nitrate, arsenic and byproduct levels this page cannot.

    How to read it

  3. Test your own tap for lead

    Your service line, solder and fixtures decide the lead at your faucet, not the utility’s average.

    Lead in your water: what to do

  4. Compare certified filters

    What the filters certified for these results cost over five years, cartridges included.

    Compare five-year costs

Other California utilities

All California utilities

Sources