Free · No accounts · Every number cited
Private well water: certified labs and official test data
Testing a private well is usually up to the owner. This site gathers the official lab lists and public well-test results so you can choose a lab and know what to test for.
457US certified labs (1 official state lists)Updated 2026-10-17
69Canadian accredited labs (2 official lists)Updated 2026-10-18
564US counties with arsenic/nitrate well results (13 states)Updated 2026-10-18
74Quebec municipalities with private-well resultsUpdated 2026-10-17
Arsenic and nitrate in sampled wells, by county
All counties →% of sampled wells above the limit
0–1%1–5%5–10%10–25%25–50%50%+
Not measuredNo published dataStart here
US labs by stateLabs certified by each state for drinking-water testing, from the official state lists.Canada labsAccredited and provincially listed labs, including labs that take samples from private wells.US county arsenic & nitrateShare of sampled wells above the EPA limits, by county, from USGS/EPA Water Quality Portal data.Quebec wellsArsenic, nitrate and other results from Quebec private-well groundwater studies, by municipality.Test helperAnswer a few questions and get a list of tests that fit your well and area.Test costsPublished prices for common well-water tests, each with its source and date.If a result is highWhat to do about bacteria, nitrate, arsenic, lead, manganese or uranium, with official sources.Salesperson checklistSomeone offering a “free” water test? What EPA and state health departments say to check.Yearly reminderGet one email a year reminding you to test your well. Unsubscribe any time.
What to test and why
| Test | Why it matters | US limit (EPA) | Canada limit (Health Canada) |
|---|---|---|---|
| Bacteria (total coliform, E. coli) | A sign of sewage or surface water getting in. Test every year and after floods or repairs. | Zero (MCLG) | None detectable per 100 mL |
| Nitrate | From fertilizer, manure and septic systems. Dangerous for babies under 6 months. | 10 mg/L as nitrogen | 10 mg/L as nitrate-nitrogen (45 as nitrate) |
| Arsenic | Occurs naturally in rock. Has no taste or smell, and long-term exposure raises cancer risk. | 0.010 mg/L (10 µg/L) | 0.010 mg/L (as low as reasonably achievable) |
If a result is above a limit: bacteria · nitrate · arsenic · all guides
Source: official state and provincial lab lists, USGS/EPA Water Quality Portal (public domain), Données Québec PACES (CC-BY 4.0), US EPA and Health Canada limits. View all data sources
Sources, checked 2026-10-18: US EPA – National Primary Drinking Water Regulations · Health Canada – Guidelines for Canadian Drinking Water Quality, summary table