I have a 3 zone irrigation system, zone 1 & 3 work fine, zone 2 does not. The tops of the heads get wet but do not pop up, contacted a repair person who said "you can fix that yourself" dig up each head, turn on water, if water comes up, put back togather and go on to the next one, when you find one or more that don't get water, don't try to fix them just take to hardware store and get replacements. Simple right well spent most of yesterday and today doing just that, didn't say what to do if all heads get water but none pop up. I dismanted each, cleaned out sand and debris, flushed each space, covered pipe with screen to make sure nothing went in, still doesn't work. Was a lot of sand in the filters and heads themselves, our rrigation system is run by a well and Florida has much less rain than usual so thought perhaps the pressure was down, but as I said the other zones work fine. What do I do next. Thanks