Sizing to real demand
We size the unit to how much hot water your household can actually call for at once — not to a brochure figure. An undersized tankless unit is the most common way this goes wrong.
Water Heaters · Northern Virginia
Endless hot water — when the house is actually set up for it.
Quick answer
A tankless water heater heats water on demand instead of keeping a tank hot, which means endless hot water and lower standby energy loss. LeMaster Plumber installs, repairs and services tankless units for homeowners across Northern Virginia. They cost more upfront than a tank and sometimes need gas-line or venting upgrades, so the useful question is not whether tankless is better in the abstract — it is whether it fits your home, your demand and your budget.
Tankless gets sold on one idea: you never run out of hot water. That part is true. What decides whether it is the right call for your house is less exciting — how many fixtures might run at once, what your gas line can actually deliver, where the unit can vent, and how hard your water is. We would rather work through those with you than sell you a unit that disappoints.
We size the unit to how much hot water your household can actually call for at once — not to a brochure figure. An undersized tankless unit is the most common way this goes wrong.
New tankless installs and tank-to-tankless conversions, including the gas, venting, water and condensate connections the unit needs.
No hot water, lukewarm output, short cycling and error codes on existing tankless units — diagnosed properly rather than swapped part by part.
Northern Virginia’s water leaves scale inside a heat exchanger. Periodic flushing is what keeps a tankless unit delivering its rated output for its full life.
If a tank is the better fit for your house and how you use hot water, we will tell you that. We install both.
Being clear about the edges of a job is how you avoid a surprise halfway through it:
Fixture count, simultaneous demand, incoming water temperature, gas supply, venting route and condensate drainage all decide what can go in.
You get a specific unit, a specific scope — including any gas or venting work — and a price you approve before anything starts.
Gas sizing, combustion air, venting, isolation valves for future servicing, and condensate handling done properly, with permitting and inspection where required.
We fire it, verify temperature and flow at the fixtures, and show you how to read it and when it will need a flush.
Why LeMaster Plumber
You approve the price before we start — no surprises and no pressure. You’ll always know the cost before any work begins.
Every job is backed by proper training, the right permits, and a workmanship guarantee.
We show up on time, protect your space, and leave the job cleaner than we found it.
We quote every job upfront and you approve the price before any work begins. What we cannot do honestly is put a number on this page without seeing your situation — so here is what actually moves it:
Tankless units draw far more gas at peak than a tank. If the existing line cannot deliver it, upsizing that run is part of the job — and it is the single biggest swing factor.
A tank’s vent is rarely reusable for a tankless unit. The route, the length and whether it goes out a wall or up through the roof all matter.
Flow rate, condensing versus non-condensing, and gas versus electric are all different price points.
A condensing unit produces acidic condensate that needs a drain and usually neutralisation.
Replacing an existing tankless unit is far simpler than converting from a tank for the first time.
Water heater replacement is permitted work in Fairfax County; the permit and inspection are part of a proper job.
Hard water shortens the interval between descalings, and some homeowners choose to address that at the same time.
Water heater replacement in Fairfax County is permitted work, and a tankless conversion adds gas and venting to the scope — which is precisely the part inspection exists to catch. Our guide to water heater permits in Fairfax County covers what the process involves.
Sizing and gas capacity are not paperwork problems, they are safety and performance problems: a tankless unit starved of gas will not deliver its rated output, and improper venting of a combustion appliance is dangerous. Both are reasons this is not a do-it-yourself swap, and reasons to be sceptical of a quote that does not mention either.
On hard water: Fairfax Water is the drinking-water utility for much of the area we serve, and scale from mineral content is the main cause of lost output in a tankless heat exchanger over time. That is a maintenance-interval question rather than a code question, but it belongs in the decision.
Ready to get it sorted? Pick your own appointment time online.
Or call (703) 832-9090 — we answer 24/7.
We cover all of Fairfax County — Fairfax, Centreville, Chantilly, Vienna, Reston, Herndon, Burke, Springfield, McLean, Annandale and every community in between — plus Ashburn, Sterling and South Riding in Loudoun, and neighboring Arlington, Alexandria, Falls Church and Manassas.
It depends on your house. Tankless units deliver endless hot water and use less standby energy, which can lower bills over time, but they cost more upfront and sometimes need gas-line or venting upgrades. They are a strong fit for households that run out of hot water, or where floor space is tight. For a small household with a tank that meets demand, the payback case is much weaker.
A well-maintained tankless unit can last 20 years or more, against roughly 8 to 12 for a conventional tank. The words doing the work in that sentence are “well maintained” — hard water and skipped descaling shorten it considerably.
Yes, more than a tank does. Northern Virginia’s water leaves mineral scale inside the heat exchanger, and periodic flushing is what keeps output and efficiency where they should be. If a unit was installed without isolation valves, servicing it is harder than it needs to be — we fit them as standard.
Often, yes, on a first conversion from a tank. A tankless unit’s peak gas demand is much higher than a tank’s, and an undersized supply line means the unit cannot reach its rated flow. We check this before quoting, because finding out afterwards is how conversions go wrong.
Frequently — reclaiming that floor space is one of the better reasons to convert, and it is a common ask in the area’s townhomes and condos. What decides it is whether a compliant venting route and adequate gas supply can reach the space. We look before we promise.
In most cases we can diagnose and replace a failed water heater the same day you call. A tankless conversion may take longer if gas or venting upgrades are needed, and we would rather tell you that upfront than start and stop.
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