The key to adequate flushing is to provide an open-line flushing velocity of at least 1 foot per second at the end of the drip line. For a 5/8-inch-diameter lateral, a flow rate of 1 gallon per minute at the end of the lateral is required to achieve that velocity. A flow rate of 2 gallons per minute is needed for a 7/8-inch-diameter drip line. You may have to determine by trial-and-error the number of laterals that you can be flush at the same time and still maintain the desired flushing flow rate.
Flushing practices for row crop drip systems often are different from those for permanent crop drip systems are often different due to differences in drip system design. For additional flushing information, see Row Crops or Tree and Vine Crops.