Your utility is not your tap

EPA's SDWIS data covers what a water system delivers at the point it leaves the utility's control, tested at the treatment plant and at points in the distribution system. It cannot see the plumbing inside any one building - lead solder in an older home, a corroding service line, or a neglected filter, all of which happen after the utility's own testing point.

Testing frequency is not equal

Larger systems test far more often than small ones, simply because EPA requires more frequent monitoring at higher population tiers. A "no violations" record on a system serving 3,000 people reflects fewer tests than the same record on a system serving 300,000 - real, but weaker, evidence.

If you want a direct answer

A certified home water test is the only way to know what's actually coming out of your own tap. EPA's Safe Drinking Water Hotline (1-800-426-4791) can point to state-certified labs.

Where to go next

Real systems this plays out on: PORTLAND WATER BUREAU, OR, CITY OF HOUSTON, TX, SFPUC CITY DISTRIBUTION DIVISION, CA.

How to Read a "No Violations" Record · What Filter Actually Addresses Each Kind of Violation