The Safe Drinking Water Act (SDWA) gives the EPA authority to set and enforce water quality standards for public water systems. The definition of “public” matters here: systems that serve at least 25 people or have at least 15 service connections. Private wells that serve a single household are explicitly carved out of that definition.
Your municipal water utility gets inspected, tested, and must publish results every year. Your private well gets none of that. No federal inspector is coming. No federal agency requires you to test it.
What This Means in Practice
About 43 million Americans drink from private wells, according to USGS estimates. Every one of them is drinking unmonitored groundwater from a regulatory standpoint.
When your public utility has a contamination event, they’re legally required to notify you within 24 hours for acute health risks and within 30 days for longer-term risks. Your private well has no such notification system. If arsenic in your aquifer creeps above 10 ppb over five years, nothing alerts you. You’d only know if you tested.
That’s the practical consequence of the regulatory gap.
What the EPA Does Say (Voluntarily)
The EPA publishes guidance for private well owners recommending annual testing for bacteria (total coliform, E. coli) and nitrates. This is guidance, not law. No federal agency will fine you for skipping it. The EPA also recommends testing after flooding, after septic failures, after changes in water appearance or taste, and every 3-5 years for a broader panel of contaminants.
The EPA’s private well guidance is at epa.gov/privatewells. It’s useful, but none of it is enforceable against you as a private homeowner.
State Rules Are the Only Mandatory Rules
Most states regulate private well construction: casing depth, setback distances from septic systems, casing material specifications, cap and seal requirements. These construction standards are enforced at the time of installation, typically through a permitting process.
Once the well is built and the driller certifies it, most states have no ongoing mandatory testing requirement. That changes only in specific circumstances:
Real estate transactions are the most common trigger. Most mortgage lenders require a water test at closing for properties with private wells. Many states require at minimum a bacteria and nitrate test. Some states require broader panels. If you’re selling a home with a private well, your state’s real estate regulations will specify what testing documentation you need.
Some states have added requirements around specific contamination events. After major flooding, some state health departments issue advisories directing private well owners to test before resuming water use. These are typically emergency orders, not standing regulations.
The States Doing More
Connecticut and Maine have active programs providing free or subsidized water testing to private well owners. Maine’s Drinking Water Program offers heavily subsidized testing through the state health lab. These programs recognize that private well owners, particularly in rural and lower-income communities, bear a disproportionate water quality burden without the institutional support that public water system customers receive.
The Environmental Working Group has advocated for expanding these programs nationally, arguing that the SDWA’s private well exemption creates a public health gap that falls disproportionately on rural and agricultural communities where well water contamination risks are highest.
The Resale Angle Is Real
Even if you have no personal obligation to test under your state’s current rules, testing before selling a home with a private well is standard practice and often legally required. Most mortgage lenders have their own requirements independent of state law. FHA and VA loans, in particular, have specific water quality requirements for properties with private wells.
Documenting a history of clean test results, kept on file over years of ownership, is genuinely valuable at the point of sale. It demonstrates responsible maintenance and shortens the buyer’s due-diligence process.
What You Should Actually Do
The EPA’s voluntary guidance, annual testing for bacteria and nitrates, is a reasonable minimum. Treat it the way you treat a smoke alarm check or an annual HVAC service: not because someone will fine you if you skip it, but because you’re responsible for the health of everyone who drinks from your well.
The how often to test well water page covers the full annual testing schedule and the situations that require testing outside the regular cycle. The well water testing guide covers how to find a certified lab and what each test involves.
For a mail-in option that’s easy to do without finding a local lab, see the best mail-in water tests review.