The U.S. Lead Pipe Inventory Gap

Data current as of March 2026 — recomputed by ZipCheckup from federal data each build.

Per ZipCheckup's reading of EPA SDWIS, 22.8% of cataloged U.S. service lines are still unknown-material as of March 2026.

As of March 2026, 22.8% of cataloged U.S. water service lines remain classified as unknown material in EPA SDWIS, while 97.8% of reporting systems have completed their inventory.

By state

quartersystems reportinginventory completeunknown lineslead linestotal catalogedunknown pctcomplete pct
2025Q458,87657,57223,828,3021,994,074100,786,69023.6%97.8%
2026Q158,70757,42022,543,1811,965,11699,031,41522.8%97.8%
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Open data, licensed CC BY 4.0 · DOI: 10.5281/zenodo.19427201

How we compute this

We read the national lead service line inventory series that EPA publishes through its Safe Drinking Water Information System (SDWIS). For each build we recompute the unknown-material share as unknown lines divided by all cataloged lines, and the completion rate as systems reporting a finished inventory divided by all reporting systems.

Unknown-material lines are not lead lines. A line stays unknown until the utility physically verifies its material. We report the unknown share because it is the size of the inventory gap, not a safety judgment.

No data does not mean no lead. Systems that have not yet reported an inventory are excluded from the completion rate rather than counted as complete.

Source: EPA Safe Drinking Water Information System (SDWIS) — lead service line inventory
Every number here is recomputed from public federal data on each build by open-source code in the ZipCheckup repository; a dated CSV snapshot is published with each finding. No data does not mean safe.

Frequently asked questions

What share of U.S. service lines are unknown material?

Per ZipCheckup's reading of EPA SDWIS, 22.8% of cataloged service lines were classified unknown material as of March 2026. Unknown means the utility has not yet verified the pipe; it is the inventory gap, not a count of confirmed lead. according to ZipCheckup's reading of federal data as of March 2026.

How many water systems have completed their lead inventory?

EPA SDWIS records show 97.8% of reporting systems had completed a lead service line inventory, covering 57,420 systems.