Waterflow detectors installed in sprinkler systems provide an electrical alarm when a flow of water from the system equals or exceeds that of a single sprinkler. They can be used with either open or closed signaling circuits. They may consist of a flexible vane which projects into the waterway or a pressure-sensing device. For the flexible vane type, water movement deflects the vane, and the motion is transmitted to an alarm-actuating switch after a predetermined time delay. The time delay is accomplished by the use of an instantly recycling retard. Unless otherwise noted in the listing, the flexible vane type is to be used with pipe having an inside diameter which corresponds to Schedule 40 pipe for sizes up to and including 6 in. (152 mm) or Schedule 30 pipe for sizes 8 and 10 in. (203 and 254 mm). Waterflow detectors should not be specified for those systems where the time duration of a pressure fluctuation is greater than the retard time. Instantly recycling retards will not transmit an electrical alarm until the time duration of the pressure fluctuation or waterflow past the vane of the flow detector has exceeded the predetermined time setting of 30-60 seconds. Unless otherwise noted in the listing, these detectors have 175 psi (1205 kPa) rated working pressure. ...