Tankless Water Heater in Fairfax, VA

Fairfax in brief

The City of Fairfax is an independent city and the county seat, ringed by unincorporated Fairfax County neighborhoods that share its ZIP codes. The median home in the area was built in 1967. Fairfax Water is the water utility, and Washington Gas supplies gas. Many tankless units here were added during kitchen or basement renovations, sometimes on the original gas pipe, which is why some struggle on cold mornings. Sewer inside the City is run by the City's Public Works department, which matters only if a condensate line or relief drain is being rerouted to a floor drain.

What to do now if a tankless unit is acting up

1. Read the error code on the display and photograph the model label.
2. Check the outlet and breaker feeding the unit.
3. Run one hot tap at full flow; a very low flow may not trigger the burner.
4. Inspect the cold inlet screen for scale or grit if the manual shows how.
5. Smell gas? Leave the house, then call 911 and Washington Gas at 844-WASHGAS (844-927-4427), option 1, from outside.

Symptoms and causes

Cost factors

• Diagnosis. The plumber reads the unit's error history, checks gas pressure under full fire and inspects the vent before deciding what to fix.
• Repair or replace. A flush or sensor is modest; a heat exchanger on an older unit may not be worth it.
• Permits. Inside the City, plumbing permit applications go to Code Administration at 10455 Armstrong Street, Room 208 (703-385-7830). In unincorporated areas, Fairfax County uses a Household Appliance permit for gas water heater replacements, even like-for-like, with a Chimney Vent Certification for fuel-burning appliances, and a Residential Plumbing permit for new gas piping.
• Gas pipe. Many 1960s homes need larger pipe for a whole-house burner.
• Venting. Moving off a shared chimney to a sealed sidewall vent.
• Scale control. Fairfax Water's Potomac plant results average about 7.5 grains per gallon of hardness, so service valves and a yearly flush are worth building in.