Quick answer
About 269,000 people in New Mexico (13.1% of residents) got their water from private wells in 2010, according to USGS estimates. New Mexico Environment Department runs the state’s private well guidance. NMED offers free screening of private domestic well water at Ground Water Quality Bureau water fairs (arsenic, nitrate, fluoride, iron, sulfate, pH, conductivity) and free testing at Liquid Waste Program district offices; these are screenings, not certified-lab tests.
- People on private wells
- 269,423
- Share of residents
- 13.1%
- Rank among states
- 37th
- Well users modeled above 10 µg/L arsenic
- 20.6%
Where to get your well tested in New Mexico
- New Mexico Environment Department: Private Wells, the state’s guidance for private well owners.
- Certified laboratories in New Mexico. Use a lab certified for drinking water, so results are reliable.
Free or low-cost testing
NMED offers free screening of private domestic well water at Ground Water Quality Bureau water fairs (arsenic, nitrate, fluoride, iron, sulfate, pH, conductivity) and free testing at Liquid Waste Program district offices; these are screenings, not certified-lab tests. (source)
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 20.6% of New Mexico’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 New Mexico 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 |
|---|---|---|---|
| Santa Fe County | 29,431 | 20.4% | 11.7% |
| Valencia County | 27,971 | 36.5% | 58.2% |
| Bernalillo County | 27,609 | 4.2% | 38.3% |
| Doña Ana County | 20,862 | 10.0% | 17.0% |
| Sandoval County | 16,356 | 12.4% | 38.2% |
| Rio Arriba County | 15,869 | 39.4% | 9.9% |
| Taos County | 15,204 | 46.2% | 7.8% |
| San Juan County | 11,224 | 8.6% | 8.2% |
| Lea County | 10,369 | 16.0% | 16.4% |
| McKinley County | 9,885 | 13.8% | 6.7% |
| Chaves County | 8,137 | 12.4% | 6.0% |
| Luna County | 7,959 | 31.7% | 15.0% |
Show all 33 counties
| Torrance County | 7,604 | 46.4% | 12.9% |
| Grant County | 7,558 | 25.6% | 12.3% |
| Otero County | 7,444 | 11.7% | 5.3% |
| San Miguel County | 5,939 | 20.2% | 3.9% |
| Curry County | 5,555 | 11.5% | 21.0% |
| Roosevelt County | 4,083 | 20.6% | 29.7% |
| Lincoln County | 4,010 | 19.6% | 2.6% |
| Cibola County | 3,906 | 14.4% | 10.0% |
| Socorro County | 3,866 | 21.6% | 20.3% |
| Eddy County | 3,526 | 6.5% | 6.5% |
| Sierra County | 2,799 | 23.4% | 10.5% |
| Catron County | 2,390 | 64.2% | 12.0% |
| Mora County | 1,849 | 37.9% | 3.0% |
| Union County | 1,788 | 39.3% | 5.0% |
| Hidalgo County | 1,523 | 31.1% | 9.1% |
| Colfax County | 1,447 | 10.5% | 3.0% |
| Quay County | 1,444 | 16.0% | 6.9% |
| Guadalupe County | 876 | 18.7% | 6.0% |
| De Baca County | 516 | 25.5% | 16.0% |
| Harding County | 328 | 47.2% | – |
| Los Alamos County | 96 | 0.5% | – |
Counties with the highest modeled arsenic share: Valencia County (58.2%), Bernalillo County (38.3%), Sandoval County (38.2%), Roosevelt County (29.7%), Curry County (21.0%).
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 New Mexico offer free well water testing?
NMED offers free screening of private domestic well water at Ground Water Quality Bureau water fairs (arsenic, nitrate, fluoride, iron, sulfate, pH, conductivity) and free testing at Liquid Waste Program district offices; these are screenings, not certified-lab tests.
Who oversees private wells in New Mexico?
New Mexico Environment Department (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 New Mexico?
USGS estimates about 269,000 people, or 13.1% of the population in 2010. That ranks 37th of the states covered by the estimate.
What should I test my well for in New Mexico?
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 New Mexico, so add it to the first test.
Sources
- New Mexico Environment Department: Private Wells
- New Mexico certified laboratories
- New Mexico free or low-cost testing
- 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)