The law pertaining to Backflow Prevention:

• Current EPA,   state, and local ordinances require the testing and certification of backflow preventers at installation and annually thereafter (Semi-annually for an RPZ device).
• The 1997 Standard Plumbing Code requires annual testing, or more frequently as required by the manufacturer.

• Since these devices fall under the definition of a plumbing "appurtenance", only a licensed master plumber can  legally offer services to the public to replace or repair such a Backflow Prevention device.
• Testing services can be performed by any party holding a current tester's certificate, using equipment in current calibration (annual calibration required), and using only ASSE approved test methods.
• Once a device is found to be failing the standard test, only a licensed plumber can disassemble and repair the device legally. Persons performing repairs without holding state licensure are doing so in violation of the state plumbing code.
• Furthermore, since the testing procedure requires shutting off the water supply, this becomes a critical threat to life safety, since the automatic sprinkler systems have no water supply during that period of time. An
  inexperienced "tester" may walk away from a test, leaving the fire water off, and the building Owner and occupants would never know they were at risk, until a fire started. This is where state fire protection contractor licensure comes into play.

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