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Backflow testing in Chantilly, where 20151 answers to Fairfax County’s program and 20152, the South Riding side, to Loudoun Water’s.
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Our plumbing team in front of three of our vans.
Licensed and insuredVirginia Class A contractor #2705192276
24/7 emergency serviceOften same-day, and we will tell you honestly when we can get there.
Our own plumbers, our own trucksNobody here is a subcontractor with a magnet on the door
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 Chantilly
A Chantilly address doesn’t tell you whose backflow rules you’re under. 20151, with Greenbriar, Brookfield and the streets toward Westfields, is Fairfax County, on Fairfax Water and the County’s Cross Connection Program. 20152, South Riding and East Gate, is Loudoun County and Loudoun Water’s program. Same kind of device on the same kind of sprinkler system, two sets of paperwork and deadlines.
The difference that bites comes after a fail. In 20151, a failed device has to be repaired or replaced and retested within 10 business days of the failed test, and the County only takes a report showing every device at the address passing. In 20152 the failing sheet goes to Loudoun Water too, and its clock starts with Loudoun Water’s notice, not the test. Either way, a repair and retest before the tester packs up is the shortest road to a passing report.
Replacing one differs too. Fairfax County wants a plumbing permit for every backflow preventer installed, even like for like, and the permit’s final inspection waits on the new device’s test report. Loudoun Water wants the replacement put in by a master plumber. Winter splits as well: Fairfax County lets a device come off for the winter as long as it’s back before your testing month; on the Loudoun side, taking it off means another test in spring. Draining it in place is the easy winter either way.
Greenbriar is the older corner of 20151: close to six homes in ten there went up before 1980, where the typical owner’s house in the Chantilly Census place dates from 1987. Fairfax County says many lawn sprinkler systems in the county were added after the house was finished, without proper permits, and when the device on one is the wrong kind, it’s most often a dual check, which can’t be tested. If a tester ever tells you yours isn’t testable, that’s usually why, and the County’s answer is a testable device in its place.
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 |
|---|---|---|---|---|
| South Riding | 2006 | single-family houses, about 5 in 10 | gas, about 8 in 10 | Mostly the association’s sprinklers, plus any yard system an owner added. |
| Chantilly | 1987 | single-family houses, about 6 in 10 | gas, about 5 in 10 | Sprinklers added by an owner, pools and hot tubs. |
By the numbers
From the Census Bureau’s 2020 to 2024 survey, owner-occupied homes unless it says otherwise.
When it’s time
In 20151, Fairfax County gives every property with a testable device its own testing month, picked by the County’s tax map grid, and wants the report in before that month ends. The months are spread across the whole year, so ask which one is yours rather than going by a friend’s across the county.
In a newer subdivision the builder often put in the lawn sprinklers, and the backflow device with them. Nobody tells the next owner it needs a test every year until the first notice shows up.
Anything piped to the water supply that could push water back into it gets a device: lawn sprinklers, a pool fill line, a hot tub. More yard usually means more of them.
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
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.
Loudoun Water wants testable backflow devices tested every year by a certified tester. A device that fails has 30 days from Loudoun Water’s notice to be repaired and retested, and one taken off for the winter is retested when it goes back on. 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.
In 20151 it has to be the tester. Fairfax County makes its authorized vendors submit the report themselves and won’t let them pass that job to the owner; if one tries, the County asks you to call its Cross Connection Program. In 20152, the tester gets the results to you and to Loudoun Water, and Loudoun Water’s online form sends both copies at once.
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.
Tyson was wonderful; professional, very knowledgeable, thorough and fast. He was great at telling me about what was needed, and I very much appreciated that. For the next plumbing problem we have, I will have SwiftPro on speed dial.
Where we work
Next door to Chantilly: Centreville, Aldie, Reston, Fairfax and Sterling.
Questions
Go by the ZIP. 20151 is the Fairfax County side, on the County’s Cross Connection Program. 20152, the South Riding side, is in Loudoun County on Loudoun Water’s. Your water bill settles any doubt: Fairfax Water on one side, Loudoun Water on the other. Tell us which one sent the notice when you book.
The device still owes a yearly test until it’s officially out of service, and the two sides do that differently. In 20151, a Fairfax County Cross Connections inspector verifies the removal, with the system taken out or permanently disconnected; a report marking a device not in use isn’t accepted. In 20152, Loudoun Water wants the system cut and permanently capped by a plumber or a certified irrigation contractor.
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 Chantilly 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.