Chantilly is unincorporated western Fairfax County, so commercial buildings here deal with Fairfax Water, Fairfax County sewer and Fairfax County permits, and it's one of the areas where gas can come from either Washington Gas or Columbia Gas. Office campuses, flex space and restaurants generate most of the work. Call the number on this page to be connected with a local plumber in Chantilly.

Which gas company serves a Chantilly building?
It depends on the address. Washington Gas serves most of Fairfax County, but its own territory information and the County both note pockets served by Columbia Gas, and Chantilly, on the Loudoun line, is one of the places the County names. Check the gas bill. If anyone smells gas, get the building emptied first, then call 911 and the gas company from outside; for Washington Gas that's 844-WASHGAS (844-927-4427), option 1. If the bill is from Columbia Gas, use the emergency number printed on it.
What backflow rules apply to office and flex buildings?
Fairfax County's Cross Connections Group runs the program with Fairfax Water. Testable assemblies must be tested when installed, after any repair or relocation, and at least once a year by a DPOR-certified Backflow Prevention Device Worker on the County's Authorized Vendor List. Fire sprinkler systems and irrigation are both covered, so a typical office park or flex building near the Udvar-Hazy Center or along Route 50 has several assemblies to keep current. A failed test usually means rebuilding the assembly with new parts and retesting it the same visit if possible.
Who fixes what when water or sewer fails?
Fairfax Water owns the meter, while the line from the meter or street valve to the building's main shutoff belongs to the owner. On the sewer side, the County owns the mains and the owner owns the private lateral, which the County doesn't locate. If sewage backs up with no fixtures running, call the County at 703-323-1211 first; if the main is clear, it's a plumber's job. Fairfax Water's water runs moderately hard to hard, so commercial water heaters here benefit from regular flushing. The County requires a permit for water heater replacement and for new or relocated plumbing and gas fixtures, filed in PLUS.
Local note
The median home in Chantilly was built in 1987, and many commercial buildings are of similar vintage, so original water heaters, flush valves and backflow assemblies are reaching replacement age together. Planning those replacements between leases is easier than handling them as emergencies.
Commercial Plumbing questions in Chantilly
What should employees do if they notice a gas odor?
Do fire sprinkler and irrigation connections need backflow protection?
Who owns the water line between the meter and the building?
Can the work happen at night or on a weekend so we stay open?
More plumbing services in Chantilly
Commercial Plumbing nearby
Helpful guides
Sources
- Washington Gas: service territory
- Fairfax County: utility and cable providers
- Fairfax Water: water quality
- Fairfax County LDS: cross connections and backflow prevention
- Fairfax Water: your plumbing
- Fairfax County Wastewater Management
- Fairfax County LDS: when a permit is required
- Washington Gas: safety and the emergency leak line
- Chantilly housing by year built
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