Laterals in permanent crops are in most cases flushed by hand, with several (but usually fewer than 10) lateral line ends opened at a time and allowed to flush clean. Opening only a few lateral lines at once will ensure adequate flow to thoroughly flush the lines. Flushing should initially be done every 2 to 3 weeks. If the lines do not flush clean within a minute or two, more-frequent flushing may be needed. If the lines appear clean when flushed at 2- to 3-week intervals, you may be able to flush less frequently.
Self-flushing lateral line end caps are also used in microirrigation systems for permanent crops. The end caps are normally open, but they close when the system reaches a certain pressure. This allows a short flushing at the beginning and end of the irrigation. Periodic manual flushing is still recommended in these systems since flushing end caps do not provide a thorough, high-velocity flush. In some instances, self-flushing end caps may not close completely and may leak.