A filter for use with overhead sprinkler irrigation systems is disclosed. The filter includes a hollow cylindrical body, a removable screen, and a manually-actuated plunger adjacent the screen. The plunger is positioned for reciprocal movement through a debris outlet between an open, debris-discharging position, and a closed filtering position. The plunger defaults to the closed filtering position by pressurized water flowing through the body. The water is simultaneously filtered through the screen and passes out a clean water outlet while debris accumulates within the body. The plunger may be manually retracted to the open, debris-discharging position at any time, whereby accumulated debris is flushed out of the body through the debris outlet by residual water flowing therethrough.