Question
Hey Jim, I have 2 valves running the back yard and 3 running the front.  There are 2 seperate control modules for both fornt and back.  The front sprinkler system came with the house and the other was installed by a profesional landscaper.  All of the sudden there is almost no water pressure getting to the sprinklers in the front or back.  Water seems like its getting to the right zone but only enough to form a little puddle around the sprinkler head, not enough to even consider making it rise.  Whats got me confused is that both the front and back have the same problem?  when you open the manual bleed there is no change. Just a small amount of water.  Taking the advise of our local nursery I changed the diaphragm in one of the valves but it didn't change anything.  Could the problem be the wiring?  If so, would it affect every zone?  I am both frustrated and confused and hope you might shed some light on the matter with a suggestion?  Thank you in advance for your attempted assistance.

Answer
Hey Brad, I hope this helps. To cut to the chase, it sounds like somehow you have a restriction in the main pipe that feeds you're valves. First I would check your main shut off valve for the sprinkler system. If it's an old gate valve, sometimes the gate will break inside the body of the valve, and restrict the water. Also some systems have what is called a master valve. What this is, is an automatic valve (just like the ones you have worked on) except it is installed right past your main shut off valve and before the other valves. To tell if there is one installed, look in the back of your controller, and see if there is a wire hooked to a contact marked MV for master valve. If there is no wire hooked up to the MV contact, then you probably don't have one. You could also look, or dig around the area where the main sprinkler pipe enters the ground past your main shut off valve, and see if you see anything there. As far as not having any pressure because of a wiring problem. The way a solenoid works, is when the electricity hits it, it pulls a plunger up inside the body of the solenoid, and the valve is activated. It either turns it on or it doesn't, it would not affect the pressure. Sounds like they are all going on, just no  pressure. Normally, as the diaphrams go bad, they will effect the pressure in the valves. But to tell if it is the diaphram, all you have to do is unscrew the bleed screw, and bleed the valve manually. By doing this the valve should have full pressure, no matter if the diaphram is good or not. Now if it doesn't have any pressure when it is working from the clock, but when you bleed it, it has plenty of pressure, then it would be the diaphram. Sounds to me like when you bled the valve manually it still didn't have any pressure. This tells me it is not the diaphram. Have you had any plumbing work done lately? I would check #1 the main turn off valve at your water meter, #2 the main turn off valve for the whole house and #3 the main turn off valve for the sprinkler system. Has the city or county done any work on the main water lines in the street lately? Has your pressure changed in the house at all? When the system is running a valve, listen at your main shut off valve for the sprinkling system and listen for any kind of restriction or odd noise in this area. To me it doesn't sound like any of your valves are bad. It is probably some kind of restriction in the mainline, or if you do have a master valve the diaphram has gone bad in it.I really hope this helps you out, if I can be of any more help, just let me know. Thanks and have a great day.