What can cause automatic sprinkler systems to lose water pressure in most but not all stations

Question

We have 7 stations, 1 works fine, but 234 and 5 don't have much water pressure at all. What are the possibilities?

Answer 1

Dirt or stones in the line can cause problems like you describe.

This is assuming you've fully opened the manually adjustable flow valve that most sprinklers have.  

You didn't mention if this was a new installation, or if it was an existing one, if it ever worked properly.    

Answer 2

sounds to me as if you have bad diaphragms in the valves.irritrol or richdale had a bad batch about the same time as you are stating. open the valve box and listen for restriction ,hissing. if you hear this then the diaphragms will need replaced on the trouble valves. to do this ,SHUT OFF THE WATER ,remove the screws on top of the valve . remove the rubber diaphragm ,noting that the spring needs to set in the same position upon rebuild. take the rubber diaphragm to your suplyhouse to ensure exact replacement ,and ask them about proper alignment ,as you Carnot just 'throw it in' it has to be aligned a certain way.

Answer 3

Each  zone is controlled by an electronic dc valve...either you have faulty connections in your box or your the line has become contaminated with dirt .my guess would be bad connections somewhere .good luck