Low pressure irrigation on "one zone. NO pipe, or line breaks. all other zones have good pressure. Could it be the "Nelson Valve", or part therein??
Thanks

I know it appears to be low pressure but it is more likely low volume. This could be pressure in the line due to a rock or even a root of a tree gowing to close to the line. Can you post a sketch of your system showing the mainfold and all branches. Mark good branches and the bad one.