Question
Jim: moved into older house that has Nelson system with about six zones. All has worked fine until this year I hooked the backflow preventer up and turned all on. I got good pressure through b.p. And controller is working fine- no funny codes or anything. During cycle some zones don't come on and others do but with little water pressure. Do you have any insight on what may be happening? Plumbing and landscaping are my weaknesses so I will not dig up my yard (exploring)  till I hear from you. Thanks.

Answer
Hey Jim, I would suspect that the diaphrams in the valves might be going bad. first thing to do would be to check the valves off the controller, and make sure the solenoids are being activated by the controller, (listen for a humming noise). If the solenoids are working okay, then you might need to replace the diaphrams in the valves. If the solenoids re not working off the controller, then it is either the solenoids themselves, or the wires running from the controller to the valves. Go to www.irrigationtutorials.com, and this website will show you how to repair a valve, either by replacing the solenoid, or the diaphram or both. Good luck and have a great day.