EPA says to test a private well every year for total coliform bacteria, nitrates, total dissolved solids, and pH, and to test for other contaminants if you suspect them. Your local health department can tell you what's common in local groundwater.
| If this applies | Ask about testing for |
|---|---|
| Plumbing or service lines that contain lead | pH, lead, copper |
| Radon in indoor air or a radon-rich region | Radon |
| Nearby intensive agriculture | Nitrate, nitrite, pesticides, coliform bacteria |
| Gas station, landfill, dry cleaner, or factory nearby | Volatile organic compounds, TDS, pH, sulfate, chloride, metals |
| Stained fixtures or laundry | Iron, copper, manganese |
| Salty taste, or a heavily salted road nearby | Chloride, TDS, sodium |
The full checklist has EPA's whole table, plus PFAS and naturally occurring contaminants like arsenic (ask your state or local health department whether they're common where you're buying).
| Contaminant | EPA limit (public water) |
|---|---|
| Nitrate (as N) | 10 mg/L |
| Arsenic | 0.010 mg/L (10 ppb) |
| Lead | Action level 0.015 mg/L; 0.010 mg/L for public systems from Nov 1, 2027 |
| PFOA / PFOS | 4.0 ng/L each (2024 rule; changes proposed May 18, 2026) |
Private wells aren't required to meet these, and your state may use different numbers.
EPA says to use labs certified for drinking water testing; it links to every state's lab certification program. EPA notes your local health department may test private wells for free.
Get the Well Buyer's Checklist (PDF), $9
Instant download. 14-day no-questions refund. Printable checklist (PDF), Edition 1.0, US.
In New York? After the results come back, Read Your Well Test: New York Edition explains NY limits line by line.