Water heater flush in Fairfax.
Water heater flushes and tankless descaling in the City of Fairfax and on the county side. $99 for a tank flush right now.
- Tank or tankless, any brand
- Priced before we start
- Pay after the visit
Book a flush or a descale
City or county, Fairfax gets the same water, and it hardens in the fall.
Since January 3, 2014, when Fairfax Water bought the City of Fairfax water system, a house off Old Lee Highway and a townhouse in Fair Lakes have been drinking the same water. Fairfax Water’s 2025 lab figures ranged from 3.0 to 10.8 grains per gallon across its two plants, and the number doesn’t sit still: the Potomac plant went from 70 milligrams per liter in May to 185 in November. Late summer and fall water is the hard stuff.
What differs is the houses. The City and Mantua are mostly single-family homes, the median one built in the 1960s, where the water heater has been swapped out a couple of times and sits in the basement near a floor drain. Kings Park West runs to 1970s houses and townhouses. Fair Oaks and Merrifield are about half condo and apartment buildings, where the heater hides in a closet over a pan.
In the City about seven in ten owner homes heat with gas, and if the water heater is gas too, the flush includes the burner and the draft hood. A gas tank that pops loudly has a layer of sediment sitting right over its burner, and that’s the one we’d move up the list.
About two percent of Fairfax County homes run on private wells rather than public water, per the county. If yours is one of them there’s no utility report to lean on, and a water test gives you the hardness to plan around.
Where the water heaters are across Fairfax.
Census figures for the owner-occupied homes in each place, and what we’d look at first on a flush there.
| Place | Median home built | Most homes are | Heated with | What we’d look at first |
|---|---|---|---|---|
| Fair Oaks | 1995 | condo and apartment buildings, about 5 in 10 | gas, about 6 in 10 | Closet heaters over a pan: we flush to a bucket or the laundry drain. |
| City of Fairfax | 1966 | single-family houses, about 5 in 10 | gas, about 7 in 10 | Older houses on their second or third heater: we read the label first. |
| Kings Park West | 1976 | single-family houses, about 7 in 10 | gas, about 5 in 10 | Older houses on their second or third heater: we read the label first. |
| Merrifield | 1990 | condo and apartment buildings, about 6 in 10 | gas, about 6 in 10 | Closet heaters over a pan: we flush to a bucket or the laundry drain. |
| Fair Lakes | 1998 | townhouses, about 3 in 10 | gas, about 7 in 10 | A yearly flush, and a look at the anode rod. |
| Mantua | 1968 | single-family houses, about 7 in 10 | gas, about 7 in 10 | Older houses on their second or third heater: we read the label first. |
Fairfax houses, by the numbers
From the Census Bureau’s 2020 to 2024 survey, owner-occupied homes unless it says otherwise.
The City of Fairfax
- Median home built1966 Census
- Built before 1980about 7 in 10 Census
- Built since 2000about 2 in 10 Census
- Most homes aresingle-family houses, about 5 in 10 Census
- Heated withgas, about 7 in 10 Census
- Rentedabout 3 in 10 Census
- In the City of Fairfax, about 7 in 10 owner homes heat with gas. If the water heater is gas too, the flush includes a look at the burner and the vent.
- In the City of Fairfax, about 7 in 10 homes were built before 1980, so the water heater has been replaced at least once. The label says how old this one is, and we’ll tell you what that means.
The Fairfax County side
- Built before 1980about 3 in 10 Census
- Built since 2000about 4 in 10 Census
- Most homes arecondo and apartment buildings, about 4 in 10 Census
- Heated withgas, about 6 in 10 Census
- Rentedabout 5 in 10 Census
- On the Fairfax County side, in Fair Oaks, Fair Lakes, Mantua, Kings Park West and Merrifield, about 4 in 10 homes are in condo and apartment buildings. Those heaters usually sit in a closet over a drain pan, so we flush into a bucket or a laundry drain.
- On the Fairfax County side, in Fair Oaks, Fair Lakes, Mantua, Kings Park West and Merrifield, about 5 in 10 occupied homes are rented. Between tenants is the easy time to flush it, and to find out how old the tank is.
What a water heater flush costs in Fairfax.
Same prices as our water heater flush page, anywhere in Northern Virginia, and you pay after the visit.
- Tank water heater flush, with the plumbing check$99
- A tank flush on its own, normally$199
- Tankless descale, with the plumbing check$300
- A tankless descale, regularly$350
Both visits include a whole-home plumbing check: supply lines, shutoffs, a pressure reading, drains, toilets and traps.
One per household, owner-occupied homes, limited time. A leaking tank, or one that’s 15 years old, needs repair or replacement, not a flush.
Why people in Fairfax book a flush.
It lives in a condo closet
We flush it into a bucket or the laundry drain, not across the floor, and check the pan under it while we’re there.
It pops or rumbles
That’s water boiling under a layer of sediment on the bottom of the tank. A flush clears it out.
Nobody knows when it was last done
Which is most houses. The drain valve at the bottom of the tank has usually never been opened.
How to pick who flushes your water heater in Fairfax.
Questions worth asking anybody you call, us included.
My Fairfax house is from the 1960s. Is the water heater that old too?
Almost never. Tanks rarely make it past their mid-teens, so a 1960s house is on its third or fourth. The label gives the build date, and that tells us whether a flush is worth doing.
Do they check the anode rod and test the relief valve?
The anode is the part that corrodes so the tank doesn’t, and the relief valve is the tank’s safety valve. A flush that skips both is just draining water.
On a tankless, do they pump descaler through it?
A real descale isolates the heater at its service valves and pumps solution through the heat exchanger, then rinses it and cleans the inlet screen.
What our customers say.
I would gladly recommend them to anyone in the greater Fairfax/Alexandria area without reservation.
Had the water heater replaced and a quote for my HVAC. Both technicians were friendly and helpful. Prices were decent. Would use again.
James is a wealth of knowledge who provided a competitive estimate to replace our hot water heater. He is professional and courteous. Thank you for a great first call.
5.0 stars across 884 Google reviews. Read them on our reviews page.
Water heater flush questions from Fairfax.
Is the water in the City of Fairfax different from the county’s?
No. Fairfax Water took over the City’s system in January 2014, so both sides get the same supply: 3.0 to 10.8 grains per gallon in 2025. One yearly flush covers either side.
Why is my Fairfax water harder some months?
Because the river is. Fairfax Water’s Potomac plant measured 70 milligrams per liter in May 2025 and 185 by November. The heater sees the whole year of it, which is why we go by the high end.
How much does a water heater flush cost in Fairfax?
$99 right now for a tank, with a whole-home plumbing check. The flush on its own is normally $199. A tankless descale is $300 right now, regularly $350.
Water heater flushes in the towns next door.
- Water heater flush in Reston
- Water heater flush in Chantilly
- Water heater flush in Manassas
- Water heater flush in Alexandria
- Water heater flush in Woodbridge
More from SwiftPro in Fairfax
Book the flush, tank or tankless.
Call, or book online and pick a window. Tell us tank or tankless, and the tech brings the right gear.
SwiftPro Heating, Cooling & Plumbing is a licensed, BBB Accredited (A rating), independently owned heating, cooling and plumbing company in Chantilly, serving Fairfax and the rest of Northern Virginia. Virginia contractor license #2705192276. 5.0 stars across 884 Google reviews. SwiftPro maintains a dedicated HVAC team and a dedicated plumbing team.
SwiftPro Heating, Cooling & Plumbing, 4230 Lafayette Center Dr, Suite N, Chantilly, VA 20151, (703) 997-9757. Book online, read our reviews, or see every town we serve.