Tankless Water Heater in Chantilly, VA

Which gas utility will my tankless heater run on?

Most likely Washington Gas, which serves most of Fairfax County. Fairfax County notes that portions of Chantilly may be served by Columbia Gas of Virginia, and Chantilly sits right at the Loudoun line, so check the name on your gas bill before choosing equipment or calling about a leak. The utility matters for one practical reason beyond billing: the plumber needs to know the meter type and supply pressure to size the new gas pipe. If you ever smell gas, leave the house first, then call 911 and Washington Gas at 844-WASHGAS (844-927-4427), option 1, from outside, or the utility listed on your bill.

Do I need a permit, and who issues it?

Yes. Chantilly is unincorporated, so Fairfax County Land Development Services handles it. The County requires a permit for water heater replacement and for new, repaired or relocated plumbing or gas fixtures, with a narrow exemption for like-for-like fixture replacement in the same spot. Applications go through PLUS, with help at 703-222-0801. A tankless conversion that adds gas pipe or moves the heater is clearly on the permit side.

How much scale should I expect?

Fairfax Water supplies Chantilly from its Potomac and Occoquan plants, and some customers receive Washington Aqueduct water. The Potomac plant's results show hardness between about 70 and 185 mg/L, averaging around 128 mg/L or 7.5 grains per gallon. That will slowly coat a heat exchanger. Ask for isolation valves with service ports, which let the plumber circulate a descaling solution through the unit, so a flush takes an hour rather than a pipe-cutting job, and plan on doing it about once a year. Households with heavy use may add a scale-control cartridge.

A Chantilly note

In Franklin Farm and Greenbriar, many water heaters sit in basements with a sidewall nearby, which keeps vent runs short. Townhouse clusters near Route 50 can be tighter, with the heater in an interior closet. A plumber will check both the vent path and where condensate can drain before recommending a model, and will also confirm that the outlet near the heater is on a circuit that can stay powered through winter so freeze protection keeps working.