They are valves used for tests and maintenances in the Sprinkler systems.Thanks to the Orifis of different sizes, it is provided to create an equal flow to the flow passing through one sprinkle, and in case of a sprinkler water flow, the alarm devices in the lines are carried out for control purposes.The smallest sprinkles in the system and the test drainage valve should be equal.There is a observation glass on it to observe the flow.