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Original analyses built from official data. Every number links to its source and method.

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Data study

Radon and PFAS: only 13 labs on official state lists are certified to test water for radon

We counted which tests the 2,294 labs on 45 official state lists are certified for. Radon in water has 13 certified labs, and only these states have one in-state: Pennsylvania, California, Arizona. 39% of detailed lists have no in-state PFAS lab.

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Which states require well water testing when you sell a home? Only 3 of the 45 we checked

We sorted what official agency pages, extension pages and state law say in 45 states and territories about testing a private well at a home sale. Only 3, Maryland, Oregon, Rhode Island, require a test by law (in Maryland the buyer can waive it in writing); Connecticut and Vermont require a disclosure, and for 21 the pages we read say nothing about a sale.

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Which US states and counties require a septic inspection before you sell? 116 rules in 22 states (2026 census)

We looked for every state, county and township rule that requires a septic inspection or well test when a property is sold, and counted only those we read on an official source. We confirmed 116 rules in 22 states, most of them local; 3 states bar or limit local sale rules, and for 26 states we found none.

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What a well water test costs at state labs: prices in 14 states

We lined up the homeowner prices recorded in our fact-checked state guidance for state labs (and Georgia's university lab) in 14 states. One coliform test costs $10 (Missouri, printed as a handling fee) to $40, median $25. Each price is shown as printed, with its date.

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Testing deserts: in 9 states, millions of well users have no certified lab in their county

We combined official state lab lists with USGS county data for 9 states. In 3 of them, most private-well users live in a county with no listed certified lab, which matters most for time-limited bacteria tests.

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The Well Owner Access Index: how easy is it to get your well tested in each state?

We scored 42 state lab lists on lab coverage, lab density, homeowner marks, free programs and home-sale laws. 12,823,022 private-well users (34%) live in a county with no in-state certified lab on their state's list.

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