Quick answer
About 430,000 people in Massachusetts (6.6% of residents) got their water from private wells in 2010, according to USGS estimates. Massachusetts Department of Environmental Protection runs the state’s private well guidance. We didn’t find a free statewide well testing program in Massachusetts. Certified labs charge for each test, and some county health departments offer lower-cost bacteria and nitrate tests.
- People on private wells
- 430,373
- Share of residents
- 6.6%
- Rank among states
- 31st
- Well users modeled above 10 µg/L arsenic
- 9.7%
Where to get your well tested in Massachusetts
- Massachusetts Department of Environmental Protection: Private Wells, the state’s guidance for private well owners.
- Well water testing in Massachusetts: what to test for and how to collect a sample.
- Certified laboratories in Massachusetts. Use a lab certified for drinking water, so results are reliable.
Free or low-cost testing
We didn’t find a free statewide program in Massachusetts. Certified labs charge per test; county health departments sometimes offer lower-cost bacteria and nitrate tests.
Mail-in lab kits are another option when no local lab is convenient. See well water test kits for what home kits can and can’t tell you.
What to test for
- Every year: total coliform bacteria and nitrate.
- Before buying equipment: pH, hardness, iron, manganese and, if there’s a smell, hydrogen sulfide.
- Based on location: arsenic, uranium and radon, PFAS, and lead in older plumbing.
USGS modeling estimates that about 9.7% of Massachusetts’s private well users have water above the 10 µg/L arsenic limit. Arsenic has no taste or smell, so include it in your first test.
Private wells by county
Estimated people relying on private wells in each Massachusetts county in 2010, the share of residents that represents, and the modeled share of well users with arsenic above 10 µg/L. These are USGS model estimates (2010 population), not measurements of any well. Arsenic is hidden for counties with fewer than 500 well users.
| County | People on wells | Share | Arsenic >10 µg/L |
|---|---|---|---|
| Worcester County | 109,371 | 13.7% | 12.9% |
| Middlesex County | 52,297 | 3.5% | 16.9% |
| Plymouth County | 46,374 | 9.4% | 4.0% |
| Bristol County | 44,247 | 8.1% | 5.9% |
| Hampden County | 32,440 | 7.0% | 10.1% |
| Hampshire County | 25,057 | 15.9% | 8.8% |
| Barnstable County | 24,029 | 11.1% | 3.9% |
| Berkshire County | 23,865 | 18.2% | 3.5% |
| Franklin County | 21,612 | 30.3% | 5.4% |
| Essex County | 21,501 | 2.9% | 17.0% |
| Norfolk County | 19,395 | 2.9% | 9.0% |
| Dukes County | 4,906 | 29.7% | 5.0% |
Show all 14 counties
| Suffolk County | 3,084 | 0.4% | 11.5% |
| Nantucket County | 2,195 | 21.6% | 4.1% |
Counties with the highest modeled arsenic share: Essex County (17.0%), Middlesex County (16.9%), Worcester County (12.9%), Suffolk County (11.5%), Hampden County (10.1%).
After you get results
Enter your numbers in the test results tool to see what needs treating and in what order. The guide to reading a well water test explains units and limits.
Common questions
Does Massachusetts offer free well water testing?
We didn’t find a free statewide well testing program in Massachusetts. Certified labs charge for each test, and some county health departments offer lower-cost bacteria and nitrate tests.
Who oversees private wells in Massachusetts?
Massachusetts Department of Environmental Protection (Private Wells) publishes guidance for private well owners. Private wells aren’t covered by the federal Safe Drinking Water Act, so testing and treatment are up to the owner.
How many people use private wells in Massachusetts?
USGS estimates about 430,000 people, or 6.6% of the population in 2010. That ranks 31st of the states covered by the estimate.
What should I test my well for in Massachusetts?
Test every year for total coliform bacteria and nitrate, plus pH, hardness, iron and manganese before buying equipment. Arsenic is a known concern in parts of Massachusetts, so add it to the first test.
Sources
- Massachusetts Department of Environmental Protection: Private Wells
- Massachusetts Department of Environmental Protection: well water testing
- Massachusetts certified laboratories
- USGS data release: domestic well locations and populations served, 2000 and 2010 (Johnson, Belitz and Lombard, 2019)
- CDC Environmental Public Health Tracking: private well water data (from USGS)