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Backflow testing in Fairfax, inside the City or on the county side: your device tested, repaired if it fails, under the program your street is in.
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Licensed and insuredVirginia Class A contractor #2705192276
24/7 emergency serviceOften same-day, and we will tell you honestly when we can get there.
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The price is settled before the workYou see the number in writing before anything is taken apart
What it costs
How many devices you have and what kind they are decide the number, so there isn’t one figure that fits every house. You get one flat price per device when you book, before anyone comes out.
Yearly backflow test
One flat price per device, given when you book
Repair or rebuild after a failed test
Priced in writing before any work
New backflow preventer, installed
Priced in writing before any work
A device that fails is priced in writing before any work. Most can be rebuilt with new springs, seats or rubber parts; a body cracked by a freeze gets replaced. Either way it’s tested again afterward, which Virginia requires.
The national numbers, and what moves a price up or down, are in our backflow testing cost guide.
What’s different in Fairfax
A Fairfax address can land under either of two backflow programs, and ZIP 22030 runs right across the line between them. If the City of Fairfax sends your real estate tax bill, the City’s rules below apply; if the County does, as in Fair Oaks, Fair Lakes, Mantua, Kings Park West and Merrifield, the County’s do.
The City’s own test form has two lines worth knowing. One asks when the device was last rebuilt, with a reminder to rebuild every five years. The other covers fire sprinkler lines: call the Fire Marshal’s Office before the system goes out of service and again after, or the alarm goes off and the responsible party can face a penalty. The City also still allows an atmospheric vacuum breaker on sprinklers, the plain kind with no test cocks for a gauge. Before you book, ask Code Administration whether a device like yours needs the yearly test, and where the finished report should go.
On the county side the date on your notice comes off a map. Fairfax County gives every property a test month by its tax map grid, and the test and its report have to land in the 30 days before the due date, not earlier. Around Fairfax that puts a lot of tests in winter: most of Mantua comes due in January, Kings Park West in February and Fair Oaks between December and February, while Fair Lakes falls in July or August.
A winter month is awkward for sprinklers blown out in October. The gauge needs water on the device, so the supply gets opened for the readings and the device is drained again right after; book a mild afternoon. In Mantua, where nearly eight homes in ten went up before 1980, the sprinklers were often an earlier owner’s idea and may sit unused. The County won’t take a report marking a device not in use, so getting off the list means disconnecting the system and having a County inspector verify it.
Neighborhood by neighborhood
Census figures for the owner-occupied homes in each place, and what usually brings the test notice to houses like these.
| Place | Median home built | Most homes are | Heated with | What usually needs the test |
|---|---|---|---|---|
| Fair Oaks | 1995 | condo and apartment buildings, about 5 in 10 | gas, about 6 in 10 | The building’s fire line, tested by the association. |
| City of Fairfax | 1966 | single-family houses, about 5 in 10 | gas, about 7 in 10 | A sprinkler system or pool added later, where there is one. |
| Fairfax Station | 1982 | single-family houses, about 9 in 10 | gas, about 5 in 10 | Sprinklers added by an owner, pools and hot tubs. |
| Kings Park West | 1976 | single-family houses, about 7 in 10 | gas, about 5 in 10 | A sprinkler system or pool added later, where there is one. |
| Merrifield | 1990 | condo and apartment buildings, about 6 in 10 | gas, about 6 in 10 | The building’s fire line, tested by the association. |
| Fair Lakes | 1998 | townhouses, about 3 in 10 | gas, about 7 in 10 | Sprinklers added by an owner, pools and hot tubs. |
| Long Branch | 1968 | single-family houses, about 9 in 10 | gas, about 7 in 10 | A sprinkler system or pool added later, where there is one. |
| Mantua | 1968 | single-family houses, about 7 in 10 | gas, about 7 in 10 | A sprinkler system or pool added later, where there is one. |
By the numbers
From the Census Bureau’s 2020 to 2024 survey, owner-occupied homes unless it says otherwise.
Most of the Fairfax Station Census place, in the table, has Fairfax mail, so it counts here.
When it’s time
On the county side, a device that fails has ten business days from that test to be repaired and pass again, and the County takes no report with a failed device on it. Settle the repair that day, not after the next notice.
A letter from the water utility with a date on it means there’s a testable device on your line, usually on the lawn sprinklers, and its test is due.
On an RPZ, a little water when the pressure jumps can be normal. A steady stream from the opening underneath means a check valve isn’t sealing, and it won’t pass.
Before the first hard freeze
A device that sits full of water all winter is the most common reason it fails the spring test. Around here, get this done by the end of October.
On most houses it’s outside by the foundation: a brass valve on two pipes standing out of the ground, with a cap on top. That’s a PVB. An RPZ or double check may sit in a basement or a box in the ground instead.
Turn off the valve that feeds the sprinklers, usually in the basement or utility room just past the main shutoff. Leave the rest of the house on.
Most systems here get blown out with compressed air so nothing sits in the lines or the device. If yours hasn’t been, that’s the step that matters.
Set the device’s two shutoff handles and its little test cocks about halfway, near 45 degrees, so no pocket of water stays trapped inside to freeze.
An insulated cover helps a PVB through the winter. On an RPZ, never block the relief valve opening underneath: it has to be able to dump water.
Some owners bring the device inside for the winter. Check the rules first: Loudoun Water wants a device that came off tested again when it goes back on, and Fairfax County wants it back on before your testing month.
Not sure it was drained, or saw water coming from the cap when the sprinklers ran? Call us. We’ll look at it, and if it cracked, you get the reason and a price before anything gets replaced.
Who sends the notice
Inside the City, Fairfax Water’s cross-connection program is run by the City’s Fire Department and Code Administration, and the City’s own test report form says every testable device has to pass a test every year. Source.
The City’s lawn irrigation guideline allows three devices on a sprinkler system: an atmospheric vacuum breaker, a pressure vacuum breaker or a reduced pressure assembly, and it requires the reduced pressure assembly where chemicals are fed into the system. Source.
Fairfax County’s Cross Connection Program wants testable backflow devices on lawn sprinklers, fire sprinklers, pools and hot tubs tested every year by a tester on the County’s Authorized Vendor List. The tester files the report and the County emails you when it’s in; nothing after 14 days, and the County asks you to check with them. Source.
Each property gets its own testing month from the County’s tax map grid, and the report is due before that month ends. A device that fails has to be repaired or replaced and retested within 10 business days of the failed test, and one taken off for the winter goes back on before the testing month. Source.
Our Virginia Class A contractor license, 2705192276, is on the side of the van.
Choosing a tester
Questions to ask anybody who offers to test it, us included.
The form, the fire line call and the County’s test month all hang on it. If they don’t ask, tell them, with the month on your notice.
Since January 1, 2023, Virginia only accepts tests from a DPOR-certified Backflow Prevention Device Worker, and some places keep a list of their own on top. Ask to see the certificate before the gauge goes on.
Some utilities take it from the tester and some want it from you. Ask which, and keep a copy either way, so you can show the date if a second notice turns up.
Ask for the reason and a written price before anything gets taken apart, and whether the retest is part of it. A failed device runs on a deadline, so a tester who can also fix it saves you a second trip.
Two of our crew going over a work order before the day's calls.
From our Google reviews
5.0 stars across 1,131 reviews. Read them on our reviews page.
My technician James gave an honest assessment of my situation, clearly laid out the scope of work, and provided different pricing options to resolve my concern. I will definitely call SwiftPro in the future for any plumbing needs!
Where we work
Next door to Fairfax: Annandale, Reston, Centreville, Chantilly and Manassas.
Questions
Look at who sends your real estate tax bill, the City of Fairfax or Fairfax County. The ZIP won’t settle it, since 22030 covers streets on both sides of the line.
Fairfax County sets the month by your property’s tax map grid, and the grids around Mantua, Kings Park West and Fair Oaks come due in midwinter. Testing in the fall to dodge the cold doesn’t meet the rule, which wants it in the 30 days before the due date. Our winterizing guide covers draining the device again afterward.
One flat price per device, given when you book, before anyone comes out. How many devices you have, and whether one needs a repair, is what moves it. Our cost guide has the national numbers.
About 30 minutes a device. The water is off for a few of those minutes while the gauge readings are taken.
Ready when you are
Call, or send the form at the top. Have the notice handy: how many devices it lists and the date on it are what we need.
SwiftPro Heating, Cooling & Plumbing
4230 Lafayette Center Dr N, Chantilly, VA 20151
44679 Endicott Dr, Suite 211, Ashburn, VA 20147
Virginia Class A contractor license #2705192276
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 1,131 reviews on Google, Angi, Yelp, the BBB and Facebook. SwiftPro maintains a dedicated HVAC team and a dedicated plumbing team.
From SwiftPro Heating, Cooling & Plumbing in Chantilly. Housing figures are the Census Bureau’s American Community Survey, 2020 to 2024, for each place named; permit, water and sewer facts link to each office’s own page and were checked in September and October 2026.