Tankless Water Heater in Annandale, VA

Annandale's starting point

Annandale grew fast after World War II, and many ramblers and split-levels near Lake Barcroft and Ravensworth still have the original layout: a gas tank and furnace side by side, venting into a shared chimney, fed by gas pipe sized for those two appliances. A tankless heater changes all three. It needs its own sealed vent, more gas than a tank, and often a different location on a wall with access to the outside.

Water comes from Fairfax Water, drawn from the Potomac River and the Occoquan Reservoir. Its Potomac plant results show hardness of about 70 to 185 mg/L, averaging around 7.5 grains per gallon. Homes of this age may also have older galvanized or mixed piping inside, which a plumber will want to see before tying in new lines. Basements in these homes are often partly finished, so the plumber will also map where a condensate line can drain and where the new gas pipe can run without opening ceilings. A quick look at the electrical outlet near the heater matters too, because even gas tankless units need power for the fan and controls.

Comparing the options

Signs your setup needs a look

• The tank is old and the basement floor near it is damp
• Rust-colored hot water or a rumbling tank
• Hot water that runs out halfway through the second shower
• A shared chimney liner in poor condition

Seasonal notes

When the old tank is retired, a furnace left alone in an oversized chimney can vent poorly, so the plumber may recommend a liner check at the same time. Winter is the most demanding season for tankless sizing, so plan before the first cold snap where possible. Gas is Washington Gas: if you ever smell gas, leave the house, then call 911 and 844-WASHGAS (844-927-4427), option 1, from outside.