What Is an Approved Backflow Prevention Assembly List
What Is an Approved Backflow Prevention Assembly List
When a water utility or local health department tells you to install a backflow preventer, they are not simply asking you to find any device at a hardware store and bolt it onto the pipe. They are expecting a specific class of equipment — one that has been independently tested, certified to perform under real-world pressures, and formally listed as acceptable for use on a potable water system. That standard is enforced through what the industry calls an approved backflow prevention assembly list, and understanding how it works can save property owners and facility managers from costly compliance failures.
A close-up of a brass reduced pressure zone backflow preventer mounted on copper pipe in a commercial mechanical room, with test cocks visible and gauges attached
Why Approved Assembly Lists Exist
Backflow prevention is a public health function. When a cross-connection between a potable water line and a contaminated source allows water to flow in the wrong direction, the results can range from taste complaints to serious illness affecting entire neighborhoods. The backflow preventer sitting on your irrigation system or fire suppression line is the last mechanical barrier between your property's internal plumbing and the public drinking water supply.
Because the stakes are that high, water agencies and regulators do not simply trust that a device labeled "backflow preventer" will perform adequately. A device must prove it can reliably hold a check valve seal, drain a relief valve under backpressure, and remain testable by a certified tester under field conditions. Approved lists codify which makes and models have cleared those benchmarks.
Who Creates and Maintains These Lists
In the United States, there is no single national approved list that every utility follows. Instead, the landscape is layered:
The USC Foundation for Cross-Connection Control and Hydraulic Research, based at the University of Southern California, publishes one of the most widely referenced evaluation programs in the country. When a manufacturer wants a device recognized nationally, testing through the USC program is a common first step. The USC Manual of Cross-Connection Control sets many of the technical criteria utilities rely on when building their own lists.
The American Society of Sanitary Engineering (ASSE) and NSF International also run product testing and certification programs under their respective standards. An ASSE 1013 certification, for example, tells a utility that a reduced pressure zone assembly has been factory-tested to a defined performance standard.
State drinking water programs often maintain their own lists, drawing from USC, ASSE, or NSF evaluations but adding state-specific requirements. California, Texas, New York, and most other states publish these lists through their environmental or health agencies and update them periodically as new products are tested and older ones are retired.
Local water utilities may add a layer on top of state lists, either accepting the state list wholesale or narrowing it further based on local conditions, pipe materials in their distribution system, or past field performance of certain manufacturers.
The practical result is that the approved list governing your property depends on your location and your water provider. What is approved in one municipality may not be accepted in the next.
A water utility worker reviewing a printed backflow preventer approved device list on a clipboard while standing next to a valve vault in a commercial district
What Information Appears on an Approved List
A properly maintained approved assembly list is more than a brand name. Each entry typically includes:
- Manufacturer name and model number — often broken down by size range, since a 1-inch valve and a 4-inch valve from the same product line may be separately evaluated
- Device type — reduced pressure zone (RPZ), double check valve assembly (DCVA), pressure vacuum breaker (PVB), spill-resistant vacuum breaker (SVB), or other categories
- Approved size range — the diameter of connections for which the approval is valid
- Applicable hazard classification — whether the device is approved for high-hazard (health hazard) applications, low-hazard (non-health hazard) applications, or both
- Listing date and any expiration or renewal status
Some lists also note whether a device has been removed due to a failed field evaluation or a change in manufacturing that voided prior testing.
How to Verify Your Assembly Is Approved
The first step is identifying which governing body controls approval for your jurisdiction. If you are unsure, your local water utility's cross-connection control department can tell you which list they accept — and most utilities are required to provide that information to customers upon request.
Once you know the right list, match your existing device against it using the model number on the device's identification tag. Every backflow preventer installed in a commercial or irrigation application should carry a permanent tag showing the manufacturer, model, serial number, and size. If the tag is missing or illegible, a certified backflow tester can often identify the assembly by its physical characteristics, though replacement documentation from the installer is the more reliable solution.
If you are selecting a new device for a fresh installation, bring the list to your plumber or mechanical contractor before purchasing equipment. Installers occasionally stock devices that meet generic plumbing code but have not been evaluated under your utility's specific program. Discovering that mismatch after the pipe is soldered is an expensive correction.
What Happens If Your Device Is Not on the Approved List
A non-approved assembly will not pass a compliance inspection, even if the device functions mechanically. Your utility has the authority to require replacement with a listed assembly, and they can issue notice of violation, impose fines, or in serious cases, restrict water service until the issue is corrected.
Non-listed devices also create insurance exposure. If a contamination event is traced to a cross-connection protected only by a non-approved backflow preventer, the property owner's position in any resulting liability claim is significantly weaker than it would be had the correct equipment been in place.
A property manager and a licensed backflow tester reviewing a compliance report together outside a commercial building, comparing device information on a tablet against a posted inspection tag on a large backflow assembly
Keeping Up with List Updates
Approved assembly lists are living documents. Manufacturers retire product lines, testing standards are revised, and field failures sometimes prompt removal of previously approved models. If your backflow preventer was listed as approved five years ago, it is worth confirming it remains on the current version of your utility's list before your next required test.
Most state drinking water programs and large utilities post current approved lists on their websites and issue notifications when significant changes occur. Your certified backflow tester should also be familiar with any recent changes to the list used in your service area — that awareness is part of what a qualified professional brings to the job.
For property owners and facility managers, the simplest rule is this: before any backflow preventer is purchased, installed, or relied upon for compliance, verify it against the current approved list for your jurisdiction. The list exists to protect public health and to protect you — use it accordingly.
Sources
U.S. Environmental Protection Agency — Cross-Connection Control Manual (EPA 816-R-03-002). Office of Water, Washington, D.C. Available through the EPA's drinking water program publications.
American Water Works Association (AWWA) — Manual of Water Supply Practices M14: Recommended Practice for Backflow Prevention and Cross-Connection Control, 4th Edition. AWWA, Denver, CO.
USC Foundation for Cross-Connection Control and Hydraulic Research — Manual of Cross-Connection Control, 10th Edition. University of Southern California, Los Angeles, CA. Includes the evaluated backflow prevention assemblies list maintained by the USC FCCCHR testing program.