sorry i think i put this in the wrong area
yes i thought it was the control valve for the drip line, tried new 2 new selonoids, tried cleaning diaphram, finally replaced valve altogether, still doing it , it seems to be the filter , took it apart cleaned the filter,flushed it out but it still squeals. when i tap it it stops for a couple of seconds.but it is constant when ever the zone is running.is there anything else i can do or do i have to replace this now, thanks for your help