Title: AV-1 alarm valve.pdf
The possibility of an intermittent alarm condition is a consequence of the fact that the flow out of the system through the test valve or a single sprinkler is very small relative to the flow that can be passed through the valve. This dif- ference increases with valve size. If the system were free of trapped air, flow in would equal flow out and the Waterway Clapper would always stabilize at some open position (as needed to accommo- date the required flow). With trapped air in the system, however, the Water- way Clapper first opens wider since the system initially demands greater flow until the air pockets are compressed (back to nearly the supply pressure), and then it will tend to return closer