What California publishes about lead testing in its schools’ drinking water, what those numbers cover, and how we checked it. One row of a 51-jurisdiction survey, verified jurisdiction by jurisdiction rather than compiled from a single list.
CaliforniaComprehensive but closed
Published action level, as verified in 2026: 15 ppb
The results below are counted against that level, which the source records as set in statute.
Action levels are not comparable between jurisdictions: across the 51 we surveyed they run from 1 ppb to 20 ppb, so a share of results above “the action level” measures the threshold as much as it measures the water. We never rank states on it. Where a jurisdiction explains how its own level was set, the verified research note at the foot of this page records the explanation verbatim.
The source publishes one row per sample taken at a fixture, so every figure below counts fixture samples. A sample is counted above the action level here when its measured value is at or above 15 ppb.
41,628 non-detects + 2,350 measured = 43,978 samples collected
1.2% (517 of 43,978 samples collected) — fixtures at or above 15 ppb, the state's action level
22.0% (517 of 2,350 measured samples) — fixtures at or above 15 ppb, the state's action level
Both figures count the same 517 results at or above 15 ppb. They differ only in what that count is divided by, and dropping the rows with no measured value can only raise the rate — for a state reporting mostly non-detects it raises it by more than an order of magnitude. So we publish both denominators, and neither figure is ever shown alone.
4.1% (331 of 8,042 schools with published results) — schools at or above 15 ppb, the state's action level
The two rates above count fixture samples; this one counts schools with at least one sample at or above the level. The gap between them is itself informative, and the two units must never be mixed inside one comparison.
Sampling period: 2017-01-25 to 2020-10-02.
Testing is required by AB 746, effective 2018-01-01, which required community water systems to test every public K-12 school site built before 2010-01-01 and which closed on 2019-07-01.
Every row behind the figures above, exactly as the source published it — the verbatim result string alongside the normalised value, the non-detect flag, the state’s own action level on every row, and the sample date with no window applied.
California results (CSV) · 43,978 rows · CC BY 4.0
This page names no schools. Named readings live on the lookup, where the state’s remediation note is rendered beside every one of them.
The baseline is the National Association of State Boards of Education’s 2021 survey. Every 2026 value below was re-checked for this survey; a value that did not move is a finding too.
Nothing in this row moved between the 2021 baseline and our 2026 verification.
Our field note for California, published verbatim rather than summarised. Where it quotes a figure from a source, that is the source’s own number reproduced as we recorded it, not a rate we computed — everything we compute states its denominator and its unit.
Confirms NASBE on paper but the mandate has EXPIRED. AB 746 (effective 2018-01-01) required community water systems to test all public K-12 school sites built before 2010-01-01, by 2019-07-01. The program ENDED 2019-07-01 and its database is CLOSED to new submissions, though some districts self-tested after 2020. Results for 7,500+ schools remain published via a searchable map and, importantly, as a machine-readable dataset on the California Open Data portal (T1). Same pattern as Oregon but far larger: comprehensive coverage of a snapshot that is now seven years old. Do NOT present California as currently monitoring.
TapWaterData Editorial. "School drinking water lead testing: California." TapWaterData national school drinking-water lead testing database. Last updated 2026-08-09. Licensed under CC BY 4.0. https://www.tapwaterdata.com/school-lead-testing/california
@misc{tapwaterdata_school_lead_2026,
author = {TapWaterData Editorial},
title = {School drinking water lead testing: California},
year = {2026},
howpublished = {\url{https://www.tapwaterdata.com/school-lead-testing/california}},
note = {Last updated 2026-08-09. Licensed under CC BY 4.0}
}Published under a Creative Commons Attribution 4.0 (CC BY 4.0) licence — free to republish, chart or build on with attribution. Last updated .
All 51 jurisdictions — the national scorecard, the tier map, and the methodology behind every rating on this page.
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