Updated October 28, 2026
No, not for the report your water supplier wants. In Northern Virginia the yearly backflow test has to be done by a tester who holds a state backflow card, using a calibrated gauge, and the result goes on the supplier’s own form. A test is $250, normally $300, on our backflow testing page.
Think of your car’s yearly inspection. You might know cars inside and out, but a sticker you print at home won’t get you past a traffic stop. Only the sticker from a licensed station counts. The backflow test works the same way: the person matters as much as the result. Here’s who’s allowed, why it takes a gauge, and what you can still do yourself.
Can I test my own backflow preventer? The short answer
You can look at it, and you should. You can’t do the yearly test that counts, unless you happen to hold the state card for this exact trade yourself.
A backflow preventer is the one-way valve on your lawn sprinkler line, or sometimes on a boiler or the main water line, that keeps used water from running back into the pipes everyone shares. If you’ve never heard of it, start with what backflow is in plumbing.
Virginia’s waterworks rules say a testable device gets tested when it’s installed, right after a repair or a move, and every year after that. Your water supplier sends the yearly notice. What it wants back is a test report from a tester it recognizes, not a homeowner’s note that says it looks fine.
Who is allowed to test a backflow preventer in Virginia
Virginia treats backflow testing as its own licensed trade. The Board for Contractors at DPOR, the state office that licenses trades, lists Backflow Prevention Device Worker alongside plumbing and electrical work. Getting that card takes a class and a state exam, and DPOR says plainly that the card is mandatory, not optional.
Here’s how that plays out where you live:
- Loudoun Water made the state card a hard line on January 1, 2023. Its tester policy says a report from a tester without DPOR certification is void, and the device has to be tested again by someone who has it.
- Fairfax County adds a second layer. Its cross-connection program tells owners to hire a third party from the county’s Authorized Vendor List, and the vendor runs the test, does the paperwork and files it.
- The other suppliers, like Prince William Water and the town programs, run their own programs under the same Virginia rules. If your notice names a form or a list, that’s the one that counts. Send us a photo of it if you’re not sure.
So even a handy owner with a gauge in the garage isn’t the right person on paper. That’s the inspection sticker part: the right person has to sign it.
$250 Yearly Backflow Test
The yearly test your water utility or county asks for, on a home's backflow preventer up to 1 inch. About backflow testing
Why a backflow test takes a gauge, not a look
The parts that fail are inside. A backflow preventer is one or two spring-loaded check valves, and on an RPZ a relief valve between them. From outside, a perfectly good device and one with a worn seal look the same.
The test reads them. The tester hooks a gauge with three hoses to the test cocks, closes and opens the valves in a set order, and reads how much pressure each check holds. Each reading has a pass mark. That’s the only way to know the one-way door still shuts.
The gauge itself has to be right, too. Fairfax County’s blank test report asks for the tester’s state card number and its expiration date, plus the gauge’s maker, model, serial number and the date it was last calibrated. A hardware store pressure gauge on a hose bib doesn’t fill in any of those blanks.
Want to see every step? Read what happens during a backflow test, or how the time breaks down in how long a backflow test takes.
What your water supplier accepts as a backflow test
Each supplier wants the same basic thing: a passing result, from a tester it recognizes, on its form, on time.
- Fairfax County takes only passing reports. The test month is set by your tax map grid, the report is due within 10 business days of the test, and a failed device gets repaired or replaced and tested again within 10 business days. Its program page says the vendor submits the paperwork.
- Loudoun Water has the tester fill in its test form or online webform, and the webform emails a copy to you and to Loudoun Water. Its backflow page gives a failed device 30 days to be fixed and retested.
- Everyone else follows the same Virginia rule, and the notice you got says where the report goes.
For the full picture of the yearly rule, see why backflow testing is required every year. Your county or town page has the local details: Fairfax County, Loudoun County, Prince William County, Springfield, Leesburg and Woodbridge.
What happens if you do the backflow test yourself anyway
Say you borrow a gauge, run the steps from a video and write down good numbers. Here’s what you get:
- A report that doesn’t count. Loudoun Water calls a test from someone without the state card void. You still owe a real test.
- The overdue clock keeps running. The supplier still shows the device as untested, so the reminder letters keep coming.
- Possible water shutoff. Virginia’s rules let a water supplier discontinue service when a device isn’t tested and kept working. Loudoun Water and Fairfax County both say so too.
- A device you might have upset. Opening and closing test cocks and shutoffs out of order can leave a valve half open or stir grit into a seat.
None of that is worth it to dodge one visit. The longer version is in what happens if you skip a backflow test.
What you can do yourself between backflow tests
Plenty. None of it replaces the yearly test, and all of it helps:
- Know where it is. Most sit outside on the sprinkler line near the house, a few are in the basement where the sprinkler pipe leaves the wall.
- Keep it reachable. Trim the shrubs, move the mulch back, and don’t box it in. Fairfax County asks for clear working room around a device so a tester can get a gauge on it.
- Look at it now and then. A drip, a spray, a soggy spot or a crack after a cold night means call. The list of warning signs is in what a leaking backflow preventer means.
- Shut it down for winter. An outdoor device left full of water can crack on the first hard freeze. The steps are in how to winterize a sprinkler backflow preventer.
- Keep the notice. It has the due date and the account number the tester needs.
Leave the test cocks and the inside parts alone. That’s the tester’s side of the job.
Why SwiftPro makes the yearly backflow test easy
You don’t need a gauge or a state card. You need one phone call or one click:
- Pay $250 online, normally $300. Or call (703) 997-9757, or book a time online, whichever you like.
- We call you to pick the day. Tell us where the device is and keep your notice handy.
- We test it and tag it. A SwiftPro plumber hooks the gauge to the device, reads every check and writes the numbers down.
- We send the report where your water supplier wants it. Loudoun Water, Fairfax County, Prince William Water and the town programs each take it their own way, and yours goes in the way your notice asks.
- If it fails, you get a written quote before any repair. Nothing gets fixed until you say yes, and the device is tested again once it is.
All the details are on our backflow testing page.
Questions about testing your own backflow preventer
Can I test my own backflow preventer?
Not for the yearly report. Virginia makes backflow testing its own licensed trade, and water suppliers only accept a test from a tester with that state card, on their form.
Who can test a backflow preventer in Virginia?
A Backflow Prevention Device Worker carded by DPOR, the state office that licenses trades. Fairfax County also wants the tester’s company on its Authorized Vendor List.
Why does a backflow test need a special gauge?
The check valves are inside, so you can’t see whether they seal. A test gauge reads how much pressure each one holds, and Fairfax County’s report asks for the gauge’s serial number and the date it was last calibrated.
Can a homeowner send in their own backflow test results?
No. Loudoun Water voids a report from a tester without the state card, and Fairfax County has the vendor file the paperwork. The device would still need a real test.
Can any plumber test my backflow preventer?
Only one who also holds the state backflow card. A plumbing license by itself isn’t the same thing. Ask before you book.
What can I do myself to take care of my backflow preventer?
Know where it is, keep it clear, look for drips or cracks, shut it down before winter and keep your notice. Leave the test cocks and the inside parts to the tester.
How much does a backflow test cost?
Ours is $250 for a home device up to 1 inch, normally $300. You can pay online on our backflow testing page, and we call to pick the day.
Book the backflow test that counts
Call (703) 997-9757, book online or use the form at the top of this page. Or pay $250 online and we’ll call to pick the day. Everything is on our backflow testing page, the rest of our plumbing work is on our plumbing page, and current deals are on our offers page.
SwiftPro Heating, Cooling & Plumbing tests, repairs and replaces backflow preventers, water heaters, sump pumps and water and drain pipes, and services furnaces, heat pumps and air conditioners, across Northern Virginia from Chantilly and Ashburn, with a separate plumbing team and a dedicated HVAC team. Family owned, BBB Accredited with an A rating, 24/7 emergency service, Virginia Class A contractor license 2705192276, and rated 5.0 stars across 1,130 reviews on Google, Angi, Yelp, the BBB and Facebook. Read the reviews.
