Im new to irrigation as if last Aug. Ive learned quite a bit along the way, but want some advice. Im not sure when the irrigation was set up here in our new place but im betting 10 plus yrs ago. I have one zone that has 4 heads with the last two not popping up unless I pull them up and run it for a few minutes. Even then they are barely shooting out 4 ft. The first two heads spray out 4 times as hard. I replaced the 3rd riser with a new one thinking it was maybe clogged, but it didnt change much. I then looked at the first two heads and realized they were both different heads compared to all the other rainbird 5000's. Do you think the last two just arent getting enough pressure compared to the first two? It looks like these heads have been in there some time. Im just not sure if they were upgrading heads as to why they don't match the rest? I know the 5000's are out dated. But I don't have the time to replace all 17 heads with new ones now.
I see you haven't gotten many replies so I'll give it a try to diagnose. You have four heads on a zone and the far two are not popping up fully or spraying much. It's a safe bet that the far two are not getting enough water. Leads me to some initial suspects: there is a leak or leaks somewhere in the underground piping. There is a leak at one or more of your heads. The nozzles on one or more heads are oversized for the water supply. The far heads are internally plugged with a lot of debris (unlikely but who knows). There is a kink or other obstruction in the underground piping.
You can try capping the heads and see of you get water flow at the meter or well when you try to run the zone. If so, you have a leak. If not, check each nozzle at each rotor head. They have a little number on them. You may need a magnifying glass to read it (I usually do
). Add up the GPM of each nozzle and compare that to what your supply can handle at the desired dynamic pressure. If it's too much or marginal, you need to change to smaller nozzles.
Unscrew and remove the top cap off each rotor and see if the body is filled with muck (again, unlikely, but worth a look).
If none of the above turns out to be the issue, you might have a kink or other obstruction in the underground piping. If all of the above tests check out ok, cap the near heads and see if the far heads pop up and spray. If they don't, there is something going on underground.