Well Water in Maryland
Contaminant risks, testing requirements, and treatment recommendations for private well owners in Maryland.
Maryland Geology and Groundwater
Maryland sits on Piedmont crystalline and Coastal Plain sediments. This geology directly determines what contaminants are likely in private well water. Moderate risk exists for radon, nitrate, PFAS.
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 | Moderate risk | Some bedrock types in this state produce radon. |
| PFAS | Moderate risk | Some known contamination sites exist. Check EWG's PFAS map for your area. |
| Iron/Manganese | Moderate risk | Found in some wells depending on local geology. |
How Maryland Compares: Municipal Water Data
CheckMyTap tracks water quality for 15 cities in Maryland. While these numbers reflect municipal water (not private wells), they indicate the baseline mineral content of Maryland's water sources. Private wells often draw from the same aquifers but with less treatment.
| Metric | Maryland Average | National Average |
|---|---|---|
| Hardness | 67 PPM (moderately hard) | 170 PPM |
| Hardness range | 30 - 110 PPM | 25 - 400+ PPM |
| Lead (avg municipal) | 2.4 ppb | 3.2 ppb |
| Nitrate (avg municipal) | 1.4 mg/L | 1.1 mg/L |
| Cities with PFAS detected | 9 of 15 | ~45% nationally |
| Cities exceeding PFAS MCL (4 ppt) | 6 |
Hardest water in Maryland: Hagerstown (110 PPM), Gaithersburg (110 PPM), Bel Air (90 PPM), Glen Burnie (80 PPM), Cumberland (80 PPM).
Softest water: Salisbury (30 PPM), Annapolis (45 PPM), Waldorf (48 PPM).
Testing Requirements in Maryland
Maryland 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 Maryland: Radon in water (granitic bedrock states have higher risk)
- Recommended for Maryland: 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 Maryland Wells
Based on Maryland'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 Maryland
Maryland requires well water testing at property transfer, but all well owners should test annually. Here are your options:
- Maryland Department of the Environment (MDE) maintains a list of certified labs at mde.maryland.gov. MDE regulates all private wells in the state.
- County health departments in many Maryland counties offer low-cost well testing or can refer you to certified labs. Contact your county for specific programs.
- University of Maryland Extension provides well water education and can help interpret results through their Water Quality program.
- Home test kits provide quick screening. Use our interpreter to understand what your numbers mean.
Maryland-Specific Well Water Concerns
Regional geology creates different risks across the state
Maryland spans two distinct geological zones that determine well water quality:
- Piedmont region (central MD, including Baltimore, Frederick, and Howard counties): Crystalline bedrock wells. Higher risk for radon, iron, and manganese. Wells are typically 100-400 feet deep. Hard water is common (120-180 PPM).
- Coastal Plain (Eastern Shore, southern MD, and most of Prince George's and Anne Arundel counties): Sedimentary aquifer wells. Lower hardness, but higher nitrate risk from agricultural runoff. Wells are typically shallower (50-200 feet). Salt intrusion is a concern near the Chesapeake Bay.
PFAS contamination near military installations
Maryland has four major military installations with confirmed PFAS contamination from AFFF firefighting foam:
- Aberdeen Proving Ground (Harford County): extensive groundwater contamination documented by DoD
- Fort Meade (Anne Arundel County): PFAS detected in nearby residential wells
- Fort Detrick (Frederick County): ongoing remediation and residential well testing
- Naval Research Laboratory, Chesapeake Bay (Calvert County): testing in progress
If your well is within 3 miles of any of these installations, PFAS testing is strongly recommended. Maryland has a health advisory of 140 ppt for PFHxS. The federal MCL for PFOA and PFOS is 4 ppt each. See PFAS filter recommendations.
Maryland well construction standards
Maryland requires wells to be constructed by licensed well drillers. The MDE regulates well construction through COMAR 26.04.04. Key requirements: minimum 50-foot setback from septic systems, steel or PVC casing through the overburden, and grouted annular space. If your well was drilled before 1985, it may not meet current standards and is at higher risk for surface contamination.
Best Treatment Systems for Maryland Wells
Based on Maryland's two geological zones and the most common contaminant patterns:
Piedmont wells (central MD)
The most common setup for Piedmont wells is: sediment filter + iron/manganese filter + water softener + UV disinfection. At 120-180 PPM hardness, a salt-based softener protects plumbing and appliances. If radon is detected above 300 pCi/L, an aeration system is recommended. Water softener guide.
Coastal Plain wells (Eastern Shore, southern MD)
For Coastal Plain wells: sediment filter + carbon filter + UV disinfection + point-of-use RO for drinking water. Nitrate is the priority concern near agricultural areas. Reverse osmosis is the most effective nitrate removal method. If salt intrusion is present near the Bay, RO also addresses elevated sodium and chloride. Reverse osmosis guide.
Near military bases
Wells near Aberdeen, Fort Meade, Fort Detrick, or NRL Chesapeake Bay should prioritize PFAS removal. A certified PFAS filter (NSF P473) or under-sink reverse osmosis system is recommended for all drinking and cooking water. Whole-house GAC filtration treats every tap including showers.
Frequently Asked Questions
Is well water in Maryland safe to drink?
Well water quality in Maryland varies significantly by location and geology. Maryland sits on Piedmont crystalline and Coastal Plain sediments. No single contaminant dominates statewide, but local conditions vary. 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 Maryland?
The EPA recommends testing annually for bacteria (total coliform, E. coli), nitrate, total dissolved solids, and pH. Radon testing is also recommended in Maryland. Test more frequently if you notice changes in taste, color, or odor, or after flooding, nearby construction, or well repairs.
Does Maryland require well water testing?
Maryland 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 Maryland?
Municipal water in Maryland averages 67 PPM across 15 cities tracked by CheckMyTap, ranging from 30 to 110 PPM. Private well water typically runs 20-50% harder than city water because groundwater has more contact time with mineral formations. Many Maryland well owners have manageable hardness levels, though local variation is significant. Check your city's data.