I noticed a small leak of water when I turned on the sprinkler system this year. The leak seems to be coming from the top of the pressure vacuum breaker. Note this is not the exact picture of what I am dealing with, its the closest I could find online:
There are two screws at the top of this thing, should I be turning off the water and unscrewing these two screws...what could possibly be broken causing this leak? I really respect plumbers because boy do I hate leaks...