This commercial grade Quick Lock with flush valve is used for automatic flushing of the .700 OD drip tubing at the beginning and the end of the irrigation cycle. At the start up of the system, when reaching 0.6 GPM, the flush valve closes, and when pressure drops below 1 PSI the valve opens. To use this Quick Lock fitting, push the poly tubing over the barb and twist the sleeve over the drip tubing to secure it. The tight seal for the Quick Lock fittings is ensured by the barb, which provides a quality water-tight connection.