Backflow Testing in Maryland
Backflow Testing across Maryland: the 511 ZIP codes and 351 cities we route calls in, and who licenses plumbers in the state.
Free to homeowners in Maryland — the contractor pays us for the introduction, you never do.
Who has to test
Our backflow testing coverage in Maryland runs to 511 ZIP codes in 351 cities. In a state that mixes large systems with small ones, a testing duty that is routine on one side of a county line can be unknown on the other, and the deadline a premises is held to is whichever its own water supplier sets.
Source: coverage area as published by our call partner; place and county names from the US Census Bureau.
We route backflow testing calls in 511 ZIP codes across 351 Maryland cities, in 22 counties.
What this site is
CrossConnect is a referral service, not a contractor. We connect property owners and managers with independent contractors. Backflow assembly testing is normally restricted to testers holding a specific certification and using calibrated equipment, and the report usually has to reach your water purveyor — ask to see the certification and ask who files the report. We carry out no testing, we certify nobody, we do not set prices, and we never charge callers anything. Nothing here selects a device for any installation or states that any assembly is passing.Checking a credential in Maryland
Maryland licenses are issued by the Maryland State Board of Plumbing, Department of Labor, which publishes a public search you can use before work begins.
18 of the 21 Maryland counties we cover, from the top of the alphabet
- Anne Arundel County 37 ZIP codes
Annapolis, Glen Burnie, Pasadena, Arnold, Churchton, Crofton, Crownsville, Curtis Bay, Davidsonville, Deale, Edgewater, Fort George G. Meade, Friendship, Galesville and 15 more - Baltimore County 44 ZIP codes
Towson, Lutherville Timonium, Pikesville, Baldwin, Butler, Catonsville, Cockeysville, Dundalk, Essex, Fork, Fort Howard, Freeland, Glen Arm, Glyndon and 24 more - Baltimore City County 38 ZIP codes
Baltimore, Brooklyn - Calvert County 1 ZIP code
North Beach - Caroline County 8 ZIP codes
Denton, Federalsburg, Goldsboro, Greensboro, Henderson, Hillsboro, Preston, Ridgely - Carroll County 11 ZIP codes
Westminster, Finksburg, Hampstead, Keymar, Manchester, Marriottsville, New Windsor, Sykesville, Taneytown, Union Bridge - Cecil County 16 ZIP codes
Elkton, Cecilton, Charlestown, Chesapeake City, Colora, Conowingo, Earleville, Elk Mills, Georgetown, North East, Perry Point, Perryville, Port Deposit, Rising Sun and 1 more - Charles County 21 ZIP codes
Waldorf, Bel Alton, Benedict, Bryans Road, Bryantown, Charlotte Hall, Cobb Island, Hughesville, Indian Head, Issue, La Plata, Marbury, Mount Victoria, Nanjemoy and 5 more - Dorchester County 16 ZIP codes
Cambridge, Church Creek, Crapo, Crocheron, East New Market, Fishing Creek, Hurlock, Linkwood, Madison, Rhodesdale, Secretary, Taylors Island, Toddville, Vienna and 2 more - Frederick County 28 ZIP codes
Frederick, Adamstown, Braddock Heights, Brunswick, Buckeystown, Burkittsville, Emmitsburg, Ijamsville, Jefferson, Knoxville, Libertytown, Middletown, Monrovia, Mount Airy and 9 more - Harford County 20 ZIP codes
Bel Air, Aberdeen, Aberdeen Proving Ground, Abingdon, Belcamp, Churchville, Darlington, Edgewood, Fallston, Forest Hill, Gunpowder, Havre De Grace, Jarrettsville, Joppa and 5 more - Howard County 20 ZIP codes
Columbia, Ellicott City, Annapolis Junction, Clarksville, Cooksville, Dayton, Elkridge, Fulton, Glenelg, Glenwood, Highland, Jessup, Savage, West Friendship and 2 more - Kent County 10 ZIP codes
Chestertown, Betterton, Galena, Kennedyville, Massey, Millington, Rock Hall, Still Pond, Worton - Montgomery County 76 ZIP codes
Silver Spring, Bethesda, Gaithersburg, Rockville, Germantown, Chevy Chase, Kensington, Olney, Potomac, Takoma Park, Ashton, Barnesville, Bealsville, Boyds and 15 more - Prince George's County 63 ZIP codes
Bowie, Hyattsville, Laurel, Capitol Heights, Upper Marlboro, College Park, Greenbelt, Beltsville, District Heights, Fort Washington, Lanham, Oxon Hill, Riverdale, Suitland and 11 more - Queen Anne's County 12 ZIP codes
Barclay, Centreville, Chester, Church Hill, Crumpton, Grasonville, Ingleside, Marydel, Queen Anne, Queenstown, Stevensville, Sudlersville - Somerset County 5 ZIP codes
Crisfield, Deal Island, Marion Station, Princess Anne, Westover - Talbot County 15 ZIP codes
Bozman, Claiborne, Cordova, Easton, McDaniel, Neavitt, Newcomb, Oxford, Royal Oak, Saint Michaels, Sherwood, Tilghman, Trappe, Wittman and 1 more
3 more Maryland counties are inside the coverage area and are not listed here. If your ZIP code is in Maryland, the call reaches a contractor.
What that coverage looks like
The 22 counties in our Maryland footprint are served by many separate water suppliers, and each one decides which premises must test and how often. Anne Arundel County, with 81 covered ZIP codes, is the largest single block of them; Baltimore alone holds 37.
How a backflow testing job goes
A backflow test is a scheduled job that ends in a document. The assembly is isolated, the differential across it is measured, the result is written down, and the report goes to whoever requires it. A failed test means a repair or a rebuild and then a re-test; it does not mean the premises closes that day.
What the call asks about backflow testing
- What kind of premises it is and what is connected to the supply — irrigation, a boiler, a fire line, a commercial kitchen.
- Who is asking for the test: a water supplier, a health department, or a landlord.
- Whether there is an existing assembly with a serial number on it, and when it was last tested.
Every Maryland city we route in
96 cities, ordered by the share of buildings with twenty or more units. Containment assemblies are required building by building, and that is where the buildings are. Each page carries that city’s own numbers and the ZIP codes we route there.
- College Park 44%
- Ocean City 43%
- Chevy Chase 42%
- Bladensburg 41%
- Rockville 33%
- Bethesda 29%
- Towson 26%
- Silver Spring 25%
- Takoma Park 25%
- Hanover 21%
- Suitland 19%
- Oxon Hill 17%
- Hyattsville 15%
- Elkridge 15%
- Pikesville 15%
- Baltimore 14%
- Gambrills 14%
- Gaithersburg 14%
- Owings Mills 13%
- Derwood 12%
- Laurel 11%
- Kensington 11%
- Catonsville 11%
- District Heights 11%
- Columbia 11%
- Odenton 11%
- Temple Hills 10%
- Annapolis 10%
- Beltsville 9%
- White Plains 9%
- Riverdale 9%
- Lutherville Timonium 9%
- Ellicott City 8%
- Montgomery Village 8%
- Parkville 8%
- Jessup 8%
- Cockeysville 8%
- Upper Marlboro 8%
- Linthicum Heights 8%
- Williamsport 7%
- Salisbury 7%
- Rosedale 7%
- Gwynn Oak 7%
- Greenbelt 6%
- Fort George G. Meade 6%
- Frederick 6%
- Fort Washington 6%
- Walkersville 6%
- Capitol Heights 6%
- Nottingham 6%
- Perry Hall 6%
- Essex 5%
- Aberdeen 5%
- Cambridge 5%
- Mount Rainier 5%
- Randallstown 5%
- Middle River 5%
- Hagerstown 5%
- Halethorpe 5%
- Germantown 5%
- Reisterstown 5%
- Potomac 5%
- Severna Park 5%
- Westminster 4%
- Bel Air 4%
- La Plata 4%
- Bowie 4%
- Waldorf 4%
- Abingdon 4%
- Delmar 4%
- North East 4%
- Princess Anne 4%
- Lanham 4%
- Windsor Mill 4%
- Glen Burnie 4%
- Elkton 4%
- Chestertown 4%
- Havre De Grace 3%
- Crofton 3%
- Sparrows Point 3%
- Centreville 3%
- Hampstead 3%
- Dundalk 3%
- Pocomoke City 3%
- Brooklyn 3%
- Easton 3%
- Edgewood 3%
- Clarksburg 3%
- Rising Sun 3%
- Pasadena 3%
- Sykesville 3%
- Olney 2%
- Berlin 2%
- Clarksville 2%
- Thurmont 2%
- Forest Hill 2%
Before you call
A test is a scheduled job with a report at the end of it, not a repair. What the report has to show, and who it goes to, are on the pages above.
