SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

Close the ball valve on the outlet side of the device. Then open the water supply completely. There will always be a temporary rush of water from under the canopy, until the supply pressure seals it.

Nothing you have posted is an indication of anything being faulty or broken. That water will escape from under the canopy when the supply valve is opened is an absolute. It WILL happen. If you only open the supply valve a fraction, the water will never stop flowing from under the canopy. That is also an absolute, and not an indication of anything being faulty.

Some water supplies are on the smaller side, and those always benefit from the outlet valve of the PVB being shut completely off, before opening the supply valve to the system, and even then there will be water escaping from under the canopy, on the way to the inner poppet sealing shut tight.