Haymarket homes are mostly newer, with a median build year of 1997, so tankless conversions are usually about gas sizing and venting. Gas in town is Columbia Gas of Virginia, and permits take two steps: Town zoning approval, then Prince William County. Call the number on this page to be connected with a local plumber in Haymarket.

Who supplies gas, and what if I smell it?
The Town of Haymarket lists Columbia Gas of Virginia as its gas utility, not Washington Gas. If you smell gas near a water heater, leave the house first, then call 911 and Columbia Gas of Virginia at 1-800-544-5606 from outside. The wider 20169 Haymarket area includes large unincorporated stretches of Prince William County, so if you live outside town limits, confirm the utility on your bill.
What permits does a tankless install need?
All building permits in the town, including mechanical and plumbing, are issued by Prince William County, but only after the applicant gets Zoning Approval from the Town (Town Hall, 703-753-2600). The County's guide for gas tankless heaters in existing homes calls for a gas permit for piping and venting, a plumbing permit if water piping is extended more than 10 feet or its material changes, and an electrical permit for a new circuit. A plumber who works in western Prince William regularly will know the sequence; outside town limits, the Town step is not needed.
What is the water like?
Prince William Water supplies Haymarket. Its West System draws on the Potomac River, treated at Fairfax Water's Corbalis plant, and Lake Manassas, treated by the City of Manassas; its Bull Run Mountain and Evergreen customers are on public groundwater wells. For the hardness at your address, check Prince William Water's annual water quality report. Either way, a tankless unit should have service valves so it can be descaled, and most makers ask for a flush about once a year.
Local note
Haymarket's historic core along Route 55 is small, with older buildings, while most homes sit in newer subdivisions toward I-66. In those newer homes the heater is usually in a basement or garage near an outside wall, which keeps the vent run short; the main question is whether the builder's gas pipe can feed a whole-house burner. Heaters installed when these subdivisions were new are now reaching replacement age, so planning a conversion before the old tank fails avoids a rushed choice. Garage units should stay powered through winter so freeze protection can run.
Tankless Water Heaters questions in Haymarket
What should I do if I smell gas near the water heater?
Is a permit required to put in a tankless water heater here?
Will a gas tankless heater keep working in a power outage?
How does a plumber size a tankless heater for my household?
More plumbing services in Haymarket
Tankless Water Heaters nearby
Helpful guides
Sources
- Town of Haymarket: utility contact information
- Town of Haymarket: building/zoning permit
- Town of Haymarket: building department transfer
- Prince William County: gas-fired residential tankless water heater permit guide
- Prince William Water water quality report
- Prince William Water: water quality reports
- Columbia Gas of Virginia
- Haymarket housing by year built (city-stats.com)
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