Backflow testers field-test backflow prevention assemblies.
The ASSE 5110 practical exam — the hands-on half of the Backflow Prevention Assembly Tester standard — covers four assembly types: the reduced pressure zone (RPZ) backflow preventer, the double check valve assembly (DCVA), the pressure vacuum breaker (PVB) and the spill-resistant vacuum breaker (SVB).
The air gap is backflow protection that isn't one of the four.
This page takes each in turn, and is explicit about what its research does and doesn't hold.
RPZ: the reduced pressure zone backflow preventer
The RPZ — reduced pressure zone, also written as the reduced pressure principle backflow preventer — is the first of the four assembly types the ASSE 5110 practical exam puts candidates on.
Reaching that practical runs through ASSE's entry requirements: at least five years of documented related field experience, a 40-hour training course, a written exam, then the hands-on practical.
The route, step by step, is in our guide to how to become a backflow tester.
Which field-test procedure governs an RPZ test is a jurisdiction question.
ASSE tests its tester candidates to several published procedures — the USC 10th Edition, ASSE, EPA, Illinois, Missouri, one-hose and TREEO procedures — and some jurisdictions require a specific one.
What our research does not hold is the RPZ's own story: no fact in the vault describes how the assembly is built, how its test differs from the others', or how it fails.
That is procedure material, and it lives where testers learn it — the USC foundation's Tenth Edition Manual and its Tester Training Course, which combine lectures with hands-on wet-lab exercises, and the course you sit on the way to the practical.
This page describes the assemblies — it doesn't map them to jobs
Double check valve assembly (DCVA)
The double check valve assembly (DCVA) is the second of the four ASSE 5110 exam types.
What our research holds about it is the name and the exam place: the vault describes no DCVA-specific construction, test logic or failure behavior, so this page will not invent any.
That detail is procedure material — it lives in the field-test procedure your jurisdiction names and in the hands-on wet-lab half of a tester course.
One exam fact does the work here: ASSE's practical examines candidates on all four assembly types, so the DCVA is not a device a tester candidate can skip.
You meet it hands-on, under whatever procedure the school and your jurisdiction run.
PVB and SVB: the vacuum breakers
The pressure vacuum breaker (PVB) and the spill-resistant vacuum breaker (SVB) are the remaining two exam types.
The expansions are trade device terminology — the vault expands neither acronym and holds no fact on how the two behave differently, where either is used, or how either fails.
The difference that matters for a candidate is the same one the DCVA section made: the ASSE 5110 practical examines candidates on all four types hands-on, so the PVB and SVB are part of what you must be able to test, not background reading.
Learn them where testers learn the rest — the manual, the course and the procedure your jurisdiction requires.
Air gaps: the protection outside the exam set
The air gap is backflow protection — but not one of the four assembly types in the ASSE 5110 practical exam.
That is the fact this page can anchor.
Everything past it — what an air gap is, where one is used, how it is checked or how it fails — is outside our research, and this page won't guess at it.
What the vault does hold nearby is the division of labor in ASSE's series: survey work across a facility's cross-connections is its own standard — the 5120 Cross-Connection Control Surveyor — separate from the tester's assembly-level credential.
If a program asks you for air-gap verification, that program is the authority on what it wants confirmed; ask it.
Common failures and repairs
Common failures are the part of this topic the research cannot reach: no fact in the vault describes how any of the four assemblies fails, which parts wear out, or what a failing one does on the test kit.
That is not a gap to paper over — it is procedure and repair material, owned by the field-test procedures, the Tenth Edition Manual and the repairer side of ASSE's series.
The repairer side is real and distinct: ASSE's backflow series lists the 5130 Backflow Prevention Assembly Repairer alongside the 5110 tester, with the 5120 Cross-Connection Control Surveyor and the 5150 Program Administrator around them.
Whether repair work rides on the tester credential where you work, or on a separate repair credential, isn't something our research settles — ask the program that registers you before you advertise repairs.
What a test result sets in motion is decided by the program that requires the test — locally, your water purveyor or code authority; ask them rather than assume.
And the role-wide view of the work, the credential and the pay is in our backflow tester career guide.
Career information, not legal advice. Rules on assemblies, testing and repairs are local and change — confirm with the water purveyor, plumbing authority or licensing board that governs your work before you act on any of it.