Private well guide

Well Water in Maryland: Testing, Rules, Labs and Licensed Contractors

569,579 households in Maryland get their water from a private well. Here is what the state requires, where to get it tested, and who is licensed to work on it.

Find a certified labLicensed contractorsPick my county
143Licensed contractorschecked against state records
20Certified labsfrom the state certified list
23Counties covered
569,579Households on wells26% of households (est.)

About 570,000 Maryland households, nearly one in four, drink from a private well, a bigger share than any state around it and one of the highest in the East. Maryland is also one of the few states that actually tests the water: no new well is signed off until a certified lab passes it for bacteria, nitrate and turbidity, and the counties that sit on arsenic and radium add those too.

Who is in charge of a Maryland well

Two state bodies and 24 county health departments share the job. The Department of the Environment writes the well construction rules in COMAR 26.04.04 and certifies the laboratories; the State Board of Well Drillers licenses the master and journeyman drillers, pump installers and water conditioner installers as individuals and publishes a monthly roster; and the county health department, as MDE’s approving authority, issues the well construction permit, inspects the grouting, keeps the well completion report and issues the certificate of potability without which the house cannot be occupied. There is no state well database: your well record is at the county.

What is required, and what is left to you

A permit, a licensed driller, construction to the state standard, and a passing potability test from a certified lab before occupancy. After that it is yours: Maryland does not require retesting, and only a handful of counties look at the well again when a property changes hands. Extension’s advice is bacteria and nitrate every year and a broader chemistry check every few years, plus the tests that fit your geology: arsenic and radium in the Coastal Plain, radon in the Piedmont.

At a glance

Water test for a new wellRequired

Yes. A well construction permit from the county health department is required before drilling, the well must be built by a Maryland licensed well driller to COMAR 26.04.04 (grouted casing, 50 ft from a septic tank, 100 ft from a drainfield, minimum yields by use), and before the house can be occupied the county issues a certificate of potability based on a sample from an MDE-certified lab that passes for total coliform bacteria, nitrate and turbidity. Several counties add tests (Anne Arundel, Calvert and other Coastal Plain counties add arsenic and radium; Piedmont counties often add pH and radon screening). The driller files the well completion report with the county.

Water test when a home is soldNot required statewide

No statewide requirement. Maryland's residential disclosure asks about the water supply and known problems, and a few counties require a bacteria test or a yield test when a property on a well changes hands (check the county health department). FHA, VA and USDA loans normally require a bacteria, nitrate and lead sample from a certified lab before closing.

What the state recommends

University of Maryland Extension and MDE recommend testing a private well every year for coliform bacteria and nitrate, and every three to five years for pH, hardness, iron, manganese, lead, copper and total dissolved solids. Add arsenic and radium in the Coastal Plain (the Aquia and Patuxent aquifers under Anne Arundel, Calvert, Prince George's and the Eastern Shore), radon and uranium in the Piedmont, PFAS near Patuxent River, Fort Meade and other airfields, chloride and sodium on the lower Eastern Shore, and test again after flooding, well work or a change in taste, color or smell.

Free or low-cost testingAvailable

No free program. The county health departments do not run labs but will tell you which certified labs serve the county, and several commercial labs on the MDE list (Water Testing Labs of MD, Home Land Labs, Fredericktowne Labs, Certified Water Testing, Chesapeake Environmental) are built around homeowner samples and run the potability panel for $60 to $150. University of Maryland Extension's Wells and Septic Systems program runs periodic free screening clinics.

What the water is like

The fall line through Baltimore and Washington divides Maryland’s groundwater. West of it the Piedmont drills into fractured granite, gneiss and schist for modest yields at 100 to 400 feet; the water is soft and acidic enough to corrode copper plumbing, and the rock gives off radon and, in places, uranium. East and south of the fall line the Coastal Plain’s stacked sand aquifers give plentiful water at 50 to 300 feet on the Eastern Shore, but the shallow Columbia aquifer under the poultry counties carries nitrate, the Aquia aquifer under Anne Arundel, Calvert and the upper Shore carries naturally occurring arsenic, and the Patuxent and Patapsco under Southern Maryland carry radium, which is why those counties test for them at potability and why many wells there go 300 to 800 feet. In Washington County’s Hagerstown Valley the water is hard limestone water through karst that lets bacteria in after rain, and in Garrett and Allegany wells go into sandstone and shale with iron and sulfur. Bacteria is the test Maryland wells fail most often, everywhere.

MDE-certified labs

MDE certifies drinking water laboratories for public water systems and for the potability test, so unusually the certified list is full of labs that live on homeowner samples: Water Testing Labs of MD, Home Land Labs, Fredericktowne Labs, Certified Water Testing, Fountain Valley and Chesapeake Environmental among them, most with drop-off points across their region and mail-in bottles. Utility and treatment plant labs have been left off. Every lab below comes from the MDE certified list revised August 2026, with the tests each is certified to run.

20 certified labs

See all 20 certified labs in Maryland

Licensed well drillers, pump installers and water conditioner installers

Maryland licenses the individual, not the company. Every profile below is built from the State Board of Well Drillers roster of active licensees dated September 2026, grouped under the business each licensee works for, with the master and journeyman well drillers, pump installers and water conditioner installers named and their license numbers shown; apprentices and rig operators are counted but not named. Companies that hold only geotechnical or apprentice licenses are left off. Licenses run through June 1, 2027.

143 licensed contractors

See all 143 licensed contractors in Maryland

By county

Well use runs from 7% of homes in Montgomery County and 13% in Allegany to more than 60% in Cecil, Caroline and Calvert and nearly 70% in Garrett and Queen Anne’s. Each county page carries its well population, the nearest certified labs and the licensed contractors based there.

Maryland well water questions

Do I need a permit to drill a well in Maryland?

Yes. The county health department issues the well construction permit, the driller must hold a State Board license, and the county inspects the well and issues a certificate of potability after a certified lab passes the water for bacteria, nitrate and turbidity (plus arsenic, radium or other tests in some counties).

Is a water test required when I sell my house?

Not by the state. A few counties require a bacteria or yield test at transfer, and government-backed mortgages require a bacteria, nitrate and lead test before closing, so most sales include one.

How do I find the record for my well?

Call the environmental health office of the county health department where the well is; it holds the well completion report and permit file. Maryland has no statewide online well database.

Which lab should I use?

Any lab on the MDE certified list below. For the yearly bacteria and nitrate check, the homeowner-focused labs with local drop-off points are the easiest; for arsenic, radium, radon, VOCs or PFAS, pick a lab certified for that group.

My county tested for arsenic when the well was drilled. Do I need to keep testing?

Yes, every few years. Arsenic and radium levels in Coastal Plain wells change slowly but they do change, and a treatment unit installed to pass the potability test needs its own yearly check to prove it is still working.