Tankless Water Heater in McLean, VA

McLean conditions for a tankless install

McLean is unincorporated Fairfax County, where the median home was built in 1976. Many houses have been expanded since, adding bathrooms far from the original utility room. That pattern raises two questions with tankless: whether one unit can meet the combined flow of several showers, and how long hot water takes to reach the far end of the house.

Fairfax Water serves McLean. Its finished water comes from its own Potomac and Occoquan plants, and some customers receive Washington Aqueduct water instead. Tests from the Potomac plant put hardness at roughly 70 to 185 mg/L, averaging around 7.5 grains per gallon, so service valves and an annual flush are standard. Gas is Washington Gas, although its territory page notes that Columbia Gas serves some parts of Fairfax County; the utility on your bill is the one that matters.

One unit, two units or a tank

Signs it is time

• The existing tank is aging and sits in a finished basement where a leak would be costly
• A soaking tub drains the tank before it is full
• An existing tankless unit struggles when more than one shower runs
• Scale is visible on fixtures or the unit's inlet screen
• Hot water takes a minute or more to reach a bathroom added over a garage or in a new wing

Timing notes

Fairfax County Land Development Services issues the permit through PLUS, and the County notes a permit is needed even for a direct replacement, so build a few days into the schedule. Winter is the hardest test for a tankless unit because the incoming water is coldest, so a unit sized in summer may disappoint in February. If the job also means new gas pipe from the meter, the plumber may schedule the gas work and the heater swap on one visit so the house is without hot water for only a day. If you ever smell gas, leave the house first, then call 911 and Washington Gas at 844-WASHGAS (844-927-4427), option 1.