Tankless Water Heater in Vienna, VA

How hard is Vienna water, and what does it do to a tankless unit?

The Town of Vienna runs its own water system as a wholesale customer of Fairfax Water, with water from the Potomac River and the Occoquan Reservoir via Fairfax Water and the Washington Aqueduct. The Town describes it as moderately hard to hard, historically 5 to 10 grains per gallon (80 to 170 mg/L). At the top of that range scale builds quickly in a heat exchanger. Plan on service valves, a flush about once a year, and possibly a scale-control cartridge or softener. About a third of Town water connections are outside town limits, and other Vienna-addressed homes are on Fairfax Water directly; your bill tells you which.

What permits apply in Vienna?

Fairfax County Land Development Services issues plumbing, gas and household appliance permits through PLUS. A like-for-like gas heater swap uses a Household Appliance permit; adding gas pipe for a tankless burner calls for a Residential Plumbing permit. For properties inside town limits, the project also needs separate approval from the Town of Vienna, uploaded to the PLUS record. Addresses outside the town go through the County alone.

Will my older house need new gas pipe?

Often. With a median build year of 1971, many Vienna homes have gas pipe sized for a tank and furnace, and a water heater venting into a chimney. A tankless unit needs more gas at full fire and its own sealed vent to the outside. The good news is on the water side: the Town's service line inventory found no lead or galvanized service lines, with nearly all copper. Interior piping can still be original, so the plumber will look at the connections near the heater.

Local note

Vienna is Washington Gas territory. If you smell gas, leave the house first, then call 911 and Washington Gas at 844-WASHGAS (844-927-4427), option 1, from outside. Town water uses chloramine most of the year, with a short switch to free chlorine during hydrant flushing; that changes the taste briefly and does not affect the heater. Because Town approval and the County permit both have to clear, give the job a little extra lead time if the old tank is still working, and schedule the swap before the coldest weeks of the year.