Backflow testing is a yearly check that the valve assembly protecting the public water supply still seals. In Los Angeles, LADWP Rule 16-D requires approved assemblies to be tested at least annually by a tester credentialed by the Los Angeles County Department of Public Health. A test usually costs $75 to $150 per assembly, plus repairs. This page belongs to our guide to permits, codes and inspections, and we can arrange a local plumber to come to you with a written quote.
What does backflow testing mean for your property?
Backflow is water flowing backward in a pipe, which can pull contaminated water into the drinking supply. A backflow prevention assembly stops that, and a test confirms the check valves and relief valve inside it still work. It is a pass or fail check, done with a gauge, not a general plumbing inspection.
Many homes have no required assembly on the domestic line. They are common on irrigation systems with their own connection, fire sprinkler lines on some properties, and commercial buildings. LADWP's Rule 16-D lists the conditions that require protection, and a plumber or LADWP can tell you whether your service is one of them.
If your property has an assembly, LADWP's rule says its test records are kept for at least three years and that the department may send a periodic test and maintenance report to be completed right away. For the background, see the entry on backflow.
Who can test a backflow assembly in Los Angeles?
LADWP Rule 16-D says testing must be done by a Backflow Prevention Assembly Tester credentialed by the Los Angeles County Department of Public Health. Holding a plumbing license alone is not the same thing, so ask any tester for their county credential. Homeowners cannot test their own assembly.
That answers the common search about certification online. The testing credential is a county requirement, and a course taken at home does not replace it. If a business says it can test any assembly, ask which agency licenses its testers. Results go to LADWP on the form it provides, and the tester normally handles that.
If an assembly fails, the rule says repairs must be made and the assembly approved by a county-credentialed tester before it is considered compliant. A plumber can do the repair, and the tester retests.
How often is backflow testing required?
Annually, and sooner when LADWP asks. LADWP Rule 16-D says approved assemblies must be inspected and tested annually or more often if the department decides, and that a new or repaired assembly is tested before it counts as in compliance. A missed test can lead to a notice and, in the end, loss of service.
The rule lets LADWP deny or discontinue water service, after reasonable notice, to any premises where a required assembly is not installed, tested and maintained. In practice a notice comes first, but do not count on extra time. If you receive a notice, book a test early, because testers fill up near deadlines.
Next-day testing is sometimes available, depending on the tester and the season. Ask when you book. A same or next day visit is promised by nobody, and certain assemblies may need parts.
How much do backflow testing services cost?
Los Angeles businesses publish prices for a residential or irrigation assembly that usually run about $75 to $150 per test, with a wider range of roughly $50 to $250 depending on the assembly type and access. Repairs and parts are billed separately. The plumber inspection cost guide covers testing prices in more depth.
Price rises with:
- Reduced pressure assemblies, which have more test points than simpler ones.
- Locked gates, buried or cramped assemblies, and hard parking.
- Several assemblies on one property, though many businesses discount a group.
- Travel to outlying areas.
- Same-day or after-hours calls.
A failed test is a repair cost on top. Rubber parts, springs and seats are common replacements, and a full replacement is more. The tester or a plumber quotes the repair before doing it, and a good one explains which part failed.
When does a backflow device need a permit?
Putting in or swapping a backflow assembly on water piping typically needs a plumbing permit from LADBS, the city's Department of Building and Safety, because LADBS requires permits for installation or modification of potable water piping. Testing an existing assembly does not. Ask the plumber, and for a replacement, LADWP wants to be notified before action.
Rule 16-D says that if replacement is needed, the consumer must notify LADWP before taking action so the department can determine the protection required. Do not swap an assembly for a different type on your own.
Can a homeowner pull a plumbing permit? LADBS lists plumbing among the permits an owner can apply for, with an Owner-Builder Declaration, and requires inspections at each stage. Contractors need the C-36 plumbing classification. The same rules cover gas and water work.
What should you ask a backflow testing company?
Ask who does the test and what county credential they hold, what the price includes, how reports reach LADWP, what happens if the assembly fails, and whether repairs are quoted first. Ask when the next available visit is, without expecting a promise. Get prices in writing.
Questions on cost and scope matter more than speed. A tester who quotes a low test price and a high repair price is not saving you anything, so ask for typical repair costs for your assembly. If your property needs a larger fix, a plumber with a California contractor license should do the work, and the CSLB site lets you look up any contractor's license.
A sewer camera inspection is a related but separate service with its own price, and it is not part of a backflow test. If you also want drains or the sewer scoped by camera, ask for both on one visit to see whether the visit fee is shared.
Common questions
How long does a backflow test take?
A single residential or irrigation assembly often takes under an hour, including the paperwork. Several assemblies, hard access or a failed test with repairs take longer. The tester shuts off water briefly during the test, so plan for a short interruption. Ask about timing when you book, and whether the water will be off.
What should I ask before I hire someone for backflow testing services?
Ask for their Los Angeles County tester credential, the price per assembly, who files the report with LADWP, what a repair would cost if the device fails and when they can visit. Get the quote in writing. If a plumber is needed for repairs, look the contractor's license number up on the CSLB website.
Does someone have to be on site during the backflow test?
Not always, but somebody has to open up access to the assembly, which may sit behind a locked gate or inside a meter box, and to the water shutoff. Water is briefly off during the test. If you cannot be there, tell the tester where the device is and who can open the gate.
Is there a backflow testing cheat sheet I can use myself?
Testers use a calibrated gauge and a set procedure, and a county credential. A homeowner cannot test an assembly for compliance, so a cheat sheet will not help you. What you can do is find the assembly, keep it clear and accessible, keep the report, and book a tester before the annual deadline.
Do I need a county plumbing permit portal for this?
Not for Los Angeles. Permit portals in other counties do not apply to a property inside Los Angeles city limits, where LADBS issues plumbing permits. A routine test does not need one. A new assembly or replacement piping may, so ask the plumber and check with LADBS before work starts.