When the fire protection system is initially pressurized, water flows into the system until the water supply and system pressure become equalized, and the torsion Spring closes the Waterway Clapper in the Alarm Check Valve. Once the pressures stabilize, the Alarm Check Valve is in service and the centrally located groove in the Seat Ring is sealed. Consequently, with the Alarm Check Valve set for service, there is no flow through the alarm port to the alarm devices (i.e., water motor alarm and/or pressure alarm switch).
When there is a steady flow of water into the sprinkler system due to a sprinkler operation, the Waterway Clapper opens. Water is then permitted to flow into the centrally located groove in the Seat Ring and out through the alarm port towards the Restriction Assembly. When the flow through the Inlet Restriction of the Restriction Assembly exceeds the flow through the Outlet Restriction, the Retard Chamber (where provided for systems with variable pressure)
Subsequently, the Water Motor Alarm and/or the pressure alarm switch will be actuated. The alarms will continue
to be actuated as long as the Waterway Clapper remains open. Water in the alarm lines will automatically drain out through the 1/8 inch (3,2 mm) Drain Orifice in the Restriction Assembly when the Waterway Clapper closes (due to a stop in the flow of water into the sprinkler system).