Quick answer
About 141,000 people in Delaware (15.7% of residents) got their water from private wells in 2010, according to USGS estimates. Delaware Department of Natural Resources and Environmental Control (DNREC), with the Delaware Division of Public Health (DHSS) runs the state’s private well guidance. DNREC and DHSS offer free sampling and analysis of private drinking water wells for PFAS, nitrate, E. coli, total coliform and other standard parameters.
- People on private wells
- 141,333
- Share of residents
- 15.7%
- Rank among states
- 42nd
- Well users modeled above 10 µg/L arsenic
- 2.0%
Where to get your well tested in Delaware
- Delaware Department of Natural Resources and Environmental Control (DNREC), with the Delaware Division of Public Health (DHSS): Private Drinking Water Well Sampling Program, the state’s guidance for private well owners.
- Well water testing in Delaware: what to test for and how to collect a sample.
Free or low-cost testing
DNREC and DHSS offer free sampling and analysis of private drinking water wells for PFAS, nitrate, E. coli, total coliform and other standard parameters. (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.
Private wells by county
Estimated people relying on private wells in each Delaware 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 |
|---|---|---|---|
| Sussex County | 69,241 | 35.1% | 2.2% |
| Kent County | 43,062 | 26.5% | 1.7% |
| New Castle County | 29,030 | 5.4% | 2.0% |
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 Delaware offer free well water testing?
DNREC and DHSS offer free sampling and analysis of private drinking water wells for PFAS, nitrate, E. coli, total coliform and other standard parameters.
Who oversees private wells in Delaware?
Delaware Department of Natural Resources and Environmental Control (DNREC), with the Delaware Division of Public Health (DHSS) (Private Drinking Water Well Sampling Program) 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 Delaware?
USGS estimates about 141,000 people, or 15.7% of the population in 2010. That ranks 42nd of the states covered by the estimate.
What should I test my well for in Delaware?
Test every year for total coliform bacteria and nitrate, plus pH, hardness, iron and manganese before buying equipment. Ask the state program or a certified lab about local concerns such as arsenic, uranium or PFAS.
Sources
- Delaware Department of Natural Resources and Environmental Control (DNREC), with the Delaware Division of Public Health (DHSS): Private Drinking Water Well Sampling Program
- Delaware Department of Natural Resources and Environmental Control (DNREC), with the Delaware Division of Public Health (DHSS): well water testing
- Delaware 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)