Question: how to test rpz backflow device?
Answer: Check and if necessary, open upstream isolating valve. ... 
Connect the high pressure hose to test tap (3) ... 
Slowly open test kit valve (B) and drop the gauge. ... 
Connect – ... 
Close test kit valve (C) and open test kit valve (A) ... 
Disconnect low pressure hose from test tap(2) and reconnect to test tap (3) 2.