Nitrate is widespread in Sussex County wells.
1 widespread, 1 worth checking, 5 rare out of 7 health checks.
From 246 wells tested in Sussex County since 2000; your own well needs its own test. How to read this
Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+
Lab results: Water Quality Portal (USGS and EPA)
Who drinks from a well here
1 in 2 people 116,352 people
Nobody else tests these wells. Only you do.
People on wells: EPA researchers' 2020 estimate
How deep wells go here
Middle depth: some shelter from the surface, not complete.
Well depths: US Groundwater Well Database
Radon risk (a gas from rock)
Less likely, but the EPA still says test your air.
Radon zones: EPA map
Here's how Sussex County compares with Delaware and the counties around it.
Each result puts Sussex County next to the 6 counties that border it, on the chart's 0 to 50% scale.
This one is widespread in Sussex County wells.
Nitrate60 of 229 wells over
Too few tested to show: Cape May, NJ.
This one is worth checking in Sussex County.
Lead7 of 61 wells over
Too few tested to show: Cape May, NJ, Wicomico, MD, Worcester, MD.
These 5 are rare in Sussex County.
Arsenic2 of 60 wells over
Too few tested to show: Wicomico, MD.
Manganese6 of 180 wells over
Uranium0 of 22 wells over
Too few tested to show: Cape May, NJ, Kent, Wicomico, MD, Worcester, MD.
Radon in water0 of 18 wells over
Too few tested to show: Cape May, NJ, Wicomico, MD, Worcester, MD.
Fluoride0 of 138 wells over
Coliform bacteria turned up in 3 of 6 tested Sussex County wells, so test for it every year.
Coliform bacteria3 of 6 wells had it
E. coli0 of 4 wells had it
E. coli means human or animal waste is getting in, so if a test of your Sussex County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 34 of 241 tested wells, and it isn't a health risk.
Iron stains34 of 241 wells had it
Sussex County has 246 tested wells, and the busiest decade for testing was the 2010s.
Only 65 of the 246 wells have a test from 2020 or later, so a fresh test of your own well tells you more than any of these.
Most Sussex County wells in these records were tested for research or because someone suspected a problem, which can push the shares above what a typical home well would show (how we read the numbers).
One mail-in lab test covers the 4 things to check in Sussex County.
- Bacteria
- Nitrate
- Lead
- Arsenic
What Delaware offers well owners
- Free testingDPH offers free test kits for bacteria and ten chemical parameters, and DNREC and DHSS offer free sampling for PFAS and other contaminants to private well users. See the program
- Certified labsDelaware's list of certified labs
- Well recordsDelaware's well record search
Half the household wells here are shallower than 70 feet.
That comes from 12,124 household wells in Delaware's drilling records. Most wells of every kind here are 55 to 80 feet deep. Wells as deep as Sussex County's are usually better protected from fertilizer and bacteria at the surface, but they can pick up more of what's in the rock, like arsenic and uranium.
Look up your own well's depth in Delaware's well record search, or see how to find it.
Well depths: US Groundwater Well Database
Here's what we know about radon and PFAS in Sussex County.
Sussex County is in the EPA's lowest radon zone, so radon from well water is unlikely to be a problem. Radon guide
Between 2023 and 2025 the EPA had 20 town water systems in Sussex County test for PFAS. 9 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 36 ng/L of PFOA. Only 12 wells in Sussex County have public PFAS results, so the town systems are the best clue to what's in the groundwater nearby. PFAS guide
Radon zones: EPA Map of Radon Zones. PFAS: EPA tests of town water systems, 2023 to 2025
Questions people ask about well water in Sussex County
Is well water in Sussex County safe to drink?
60 of 229 wells tested in Sussex County had nitrate over the limit, about 1 in 4. Across Delaware it's about 2 in 10. So test your own well for nitrate before you count on it.
Can I get my well tested for free in Sussex County?
DPH offers free test kits for bacteria and ten chemical parameters, and DNREC and DHSS offer free sampling for PFAS and other contaminants to private well users. If not, use a lab Delaware has certified for drinking water. Ask for bacteria, nitrate, lead and arsenic, the tests that matter most in Sussex County.
How deep are wells in Sussex County?
Half the household wells here are shallower than 70 feet.
How does Sussex County compare with the counties around it?
For nitrate, the share of tested wells over the limit: Sussex County, at 26%, had a higher share than all 5 neighboring counties with data. Groundwater doesn't stop at county lines, so Wicomico, MD's 16% is worth knowing about if you live near it.
How often should I test my well in Sussex County?
In Sussex County, 3 of 6 tested wells had coliform bacteria, so the CDC's advice matters here: test for bacteria and nitrate every year, and right away after a flood, a repair, or any change in taste or smell.
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Where the Sussex County numbers come from
- People on wells: 116,352 in Sussex County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 1,970 well water samples from 246 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2026.
- Well depths: 12,124 Delaware drilling records for Sussex County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 6 counties that share a border with Sussex County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 20 town water systems in Sussex County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Sussex County is zone 3 on the EPA Map of Radon Zones.
- State programs and links: Department of Health and Social Services, Division of Public Health (with DNREC), checked November 1, 2026.