Well Water in Delaware
Contaminant risks, testing requirements, and treatment recommendations for private well owners in Delaware.
Delaware Geology and Groundwater
Delaware sits on Coastal Plain unconsolidated sediments. This geology directly determines what contaminants are likely in private well water. Based on this geology, Delaware well owners face elevated risk for PFAS from industrial/military sites. Moderate risk exists for nitrate.
Contaminant Risk Profile
| Contaminant | Risk Level | Why |
|---|---|---|
| Arsenic | Low risk | Generally low in this region's geology. |
| Nitrate | Moderate risk | Some areas near farmland or septic systems may have elevated levels. |
| Radon | Low risk | Not a primary concern in most of this state. |
| PFAS | Elevated risk | Military bases, industrial sites, or manufacturing in this state have contaminated groundwater. |
| Iron/Manganese | Moderate risk | Found in some wells depending on local geology. |
How Delaware Compares: Municipal Water Data
CheckMyTap tracks water quality for 5 cities in Delaware. While these numbers reflect municipal water (not private wells), they indicate the baseline mineral content of Delaware's water sources. Private wells often draw from the same aquifers but with less treatment.
| Metric | Delaware Average | National Average |
|---|---|---|
| Hardness | 31 PPM (soft) | 170 PPM |
| Hardness range | 22 - 52 PPM | 25 - 400+ PPM |
| Lead (avg municipal) | 1.3 ppb | 3.2 ppb |
| Nitrate (avg municipal) | 2.8 mg/L | 1.1 mg/L |
| Cities with PFAS detected | 2 of 5 | ~45% nationally |
| Cities exceeding PFAS MCL (4 ppt) | 2 |
Hardest water in Delaware: Dover (52 PPM), Middletown (30 PPM), Smyrna (28 PPM), Newark (25 PPM), Wilmington (22 PPM).
Softest water: Wilmington (22 PPM), Newark (25 PPM), Smyrna (28 PPM).
Testing Requirements in Delaware
Delaware does not have a statewide mandatory testing requirement for existing private wells. Regardless of state requirements, the EPA recommends testing annually for:
- Every year: Total coliform bacteria, E. coli, nitrate, pH, and total dissolved solids
- At least once: Arsenic, lead, copper, fluoride, and any contaminant identified as a local risk
- Recommended for Delaware: PFAS panel, especially if near military bases or industrial sites
- After events: Retest after flooding, well repairs, nearby construction, or any change in taste/color/odor
Recommended Treatment for Delaware Wells
Based on Delaware's geology and common contaminant risks, these treatment systems address the most likely issues:
Kills bacteria and viruses without chemicals. Recommended for all well water systems
Where to Get Your Well Tested in Delaware
Delaware has a relatively small but active private well population. Testing resources:
- Delaware Health and Social Services (DHSS) operates the Office of Drinking Water, which regulates private wells and maintains a list of certified labs.
- University of Delaware Cooperative Extension offers well water testing workshops and educational programs for homeowners.
- Delaware Geological Survey maintains well records and can provide information about aquifer conditions in your area.
Delaware-Specific Well Water Concerns
Most Delaware wells draw from the Columbia and Cheswold aquifers in the Coastal Plain. The shallow water table (often 15-50 feet) makes wells vulnerable to surface contamination, especially from agricultural runoff. Sussex County in southern Delaware has the highest nitrate contamination risk due to intensive poultry farming.
PFAS contamination has been documented near Dover Air Force Base. If you live in central Kent County, PFAS testing is recommended. See PFAS filter recommendations.
Frequently Asked Questions
Is well water in Delaware safe to drink?
Well water quality in Delaware varies significantly by location and geology. Delaware sits on Coastal Plain unconsolidated sediments. Key concerns include PFAS from industrial/military sites. The only way to know your specific water quality is to test it. Use our free interpreter to understand your results.
How often should I test my well water in Delaware?
The EPA recommends testing annually for bacteria (total coliform, E. coli), nitrate, total dissolved solids, and pH. Test more frequently if you notice changes in taste, color, or odor, or after flooding, nearby construction, or well repairs.
Does Delaware require well water testing?
Delaware does not have a statewide mandatory testing requirement for existing private wells. However, the EPA strongly recommends annual testing regardless of state requirements. Your county health department may have additional local requirements.
What is the average water hardness in Delaware?
Municipal water in Delaware averages 31 PPM across 5 cities tracked by CheckMyTap, ranging from 22 to 52 PPM. Private well water typically runs 20-50% harder than city water because groundwater has more contact time with mineral formations. Many Delaware well owners have manageable hardness levels, though local variation is significant. Check your city's data.