A backflow prevention assembly test is a field check of a prevention assembly, done with the water supplier's method in mind. EPA describes the hardware and a guideline procedure. This page only explains the idea. It is not itself a test.
Why the assembly is there
Cross connections can link a drinking water system with another supply or source that could contaminate it. EPA describes backflow as flow into potable water pipes from a source other than the intended source, and backsiphonage as backflow caused by negative pressure. Assemblies such as reduced pressure principle devices, double check valve assemblies, and vacuum breakers are used to help stop that movement. See how often to test backflow for interval context.
What the test is for
The field check verifies how the assembly is working at the site. The 2003 EPA manual says to get permission to shut the water off, identify the device, confirm flow direction, and follow the local water supplier or state method when it differs from the manual's guideline. For an RP assembly, the manual describes three checks, including a minimum of 5 psi for the first check and 2 psi for the relief opening criterion in that manual. See RPZ testing procedure and field checklist.
Where the notes go
The results are recorded in a backflow test report as a record of the field check, not as a water supplier form. Backflow Record is meant to store those notes so you can keep the assembly details, readings, and observations together. See backflow report form for the record layout.
A report in Backflow Record is a record you fill in. It is not a substitute for a licensed tester or for the form your water supplier requires. It does not report an inspection result, and it does not mean a plumbing rule was met.