Before you replace a failed water heater, check what the job involves. Gas line. Chimney. Electrical supply. Local water conditions. What the written price actually covers.
Decide whether this is a swap or a different job
When the hot water disappears, you need to know which heater can go in. First, ask the installer what failed. Ask why replacing the heater makes more sense than repairing it. Have them put the model, fuel, location, and any connections that will change in the quote. “Replace water heater” leaves too much unsettled.
For a gas tankless heater, ask which fixtures it can serve together. ENERGY STAR explains that tankless equipment is rated by hot-water flow. A storage tank's gallon capacity tells you how much it holds. A promise of continuous hot water does not mean the proposed heater can supply showers and laundry at once.
Have the installer check whether the existing gas line can supply the proposed equipment. Ask them to check whether electricity is available where needed. Settle where the exhaust gases will go. Get these checks done before you accept a conversion price.
Fairfax uses different permit routes when you need new gas piping with the appliance, as the county plumbing page explains. A tankless conversion that needs a new gas line changes more than your equipment order. Ask for that work to be spelt out in the quote. You need to know before the crew removes the old tank.
Source: U.S. Environmental Protection Agency, ENERGY STAR, Whole Home Tankless Gas Water Heaters, buying guidance; Fairfax County Land Development Services (LDS), Household Appliance (HAPL) — Residential. Both guidance pages undated; no guidance effective date stated. Gathered 2026-09-23.
A heat pump heater needs a suitable room
Fairfax's home-energy guidance suggests replacing a gas water heater with electric equipment as a way to electrify your home. It cautions that your electrical panel may need an upgrade or a subpanel to handle the added load. Have the installer check whether your electrical supply can support the proposed model. Do not assume every switch needs a new panel.
A heat pump water heater needs air. It also needs somewhere to send condensate. EPA guidance says to follow the manufacturer's airflow requirements. You also need a drain. If gravity cannot carry the water away, you can use a condensate pump. A closed closet needs a specific airflow plan. The pan beneath the heater is not where routine condensate should go.
Ask where the cooler exhaust air will go. Ask whether you will hear the equipment from an adjoining bedroom. EPA flags room layout, sound, and cool exhaust as things to consider. These details matter if your failed tank is in a finished basement or a small utility closet.
Ask for any circuit, airflow, or drain changes to be included in the quote. Before you order, have the installer show you how the proposed heater will fit. Check that it will still be accessible for servicing.
Source: Fairfax County Office of Environmental and Energy Coordination, Home Energy, Electrify Your Home; U.S. Environmental Protection Agency, ENERGY STAR, Heat Pump Water Heater Design Considerations. Both undated guidance; no effective date stated. Gathered 2026-09-23.
Settle the chimney work before the old tank leaves
For a fuel-burning replacement, get the vent certification described on the county page written into your quote. Settle who will examine the existing vent. Find out who will sign Fairfax's form. Agree who pays if the vent needs work.
The county form requires the signer to confirm that the vent or chimney is properly built. It must be the right size. It must be clear of blockages. It must have no defects or deterioration. It must work. The form also has a space to name a liner system if one was installed. It does not say every replacement needs relining. If your quote includes a liner, ask what condition or sizing problem it addresses.
Watch for a quote that simply says “reuse existing vent.” Someone still needs to check that the vent is suitable. Ask what they found. Get any extra price before you authorise more work. An allowance that does not say what it covers gives you little basis for comparing bids.
For a household-appliance permit issued through PLUS, you must have the completed form uploaded to the record. Keep a copy with your heater paperwork. Settle who will upload it. Buying the heater is one part of the job. Completing the county record is another.
Source: Fairfax County LDS, Vent/Chimney Certification, revised 2022-01-26; no separate effective date stated. Gathered 2026-09-23.
Use local water information without guessing at tank life
Fairfax Water describes its water as moderately hard to hard, typically 5–10 grains per gallon. Its guidance says hardness varies with location and rainfall. Dissolved minerals can leave deposits on appliances. That helps you discuss how to care for your replacement heater. It does not tell you how long your old heater should have lasted.
The utility's range is not a test result from your house or a private well. If someone recommends water treatment alongside the heater, ask what they measured. Ask what problem the treatment would address. Check what the heater manufacturer requires. The utility's range alone does not show that your home needs a softener.
Ask the installer to leave your model's maintenance instructions. Ask which tasks need professional servicing. If the old heater contains deposits, ask to see them. Have the contractor explain what they mean. Do not accept a promised lifespan based only on the words “Fairfax water.” We found no county-specific primary-source estimate of water-heater life or failure rates to support such a promise.
Source: Fairfax Water, How “hard” is our water?, undated utility guidance; no effective date stated. This source describes water hardness, not heater lifespan or a mandatory treatment program. Gathered 2026-09-23.
Compare the finished job, including the return visit
We found no county-specific installed-price range in the primary sources we reviewed. The permit charges covered on the county plumbing page do not tell you a contractor's equipment or labour price.
Ask for a written quote that names the heater. Get the surrounding work listed separately. That includes removing and hauling away the old equipment, changing connections, and any vent work. It also includes any electrical work needed and protection for nearby finishes. The pan requirement explained on the county page means your heater's location matters. Ask how the crew will handle it at your house.
Ask which items have a fixed price. Check which are allowances. Agree what must happen before the contractor charges for extra work. Have the contract spell out the manufacturer's equipment warranty separately from the contractor's labour cover. Settle who handles a leak or failure after the crew leaves. You need to agree these terms with the contractor. We are not saying Fairfax sets them.
For permitted work, put the inspection in your agreement too. Include any return visits. Fairfax makes the permit holder responsible for booking inspections. It sends results to the applicant and onsite contacts. Arrange to receive the result. Settle who fixes any problems the inspector finds. Agree who pays any resulting charges. Hot water at the tap does not tell you whether the inspector accepted the work.
Source: Fairfax County LDS, Building and Trade Inspections, undated guidance, no effective date stated; Virginia Board of Housing and Community Development, 13VAC5-63-210, residential pan requirement, code amendment effective 2024-01-18. Sources establish work requirements, not installed prices or warranty terms. Gathered 2026-09-23.