5 zones, 1 inch PVC pipes, spray heads that rise and extend under pressure. City water, not particularly hard as far as I am aware.

Yes, you can see from my original post that I suspect a solenoid and/or valve issue. I appreciate your time in reading and responding to my query, but it hasn't really helped me yet. I described the two valve cans in the yard. They are identical and about three feet apart. I assume they route the water pressure from one zone to the next. I can hear rushing water (but jittery--like maybe there is an obstruction in there) from one can and nothing from the other can.

Inside the cans I can see the PVC pipe. On top of that is what I assume is the valve assembly--there is a circular disc, out of which a smaller circular column rises--this little column has a cap that can be turned to release a little stream of water. Next to this is a larger, thicker plastic part that I can turn. It has two wires going to it. I haven't turned it hard yet because I haven't turned off the water yet. But can I assume that this is the solenoid? Should I try to take it out and root around in there to find some debris?

Or do I need to dig up the whole valve box?

I realize it will be hard to answer this, but please give me any tips you can and I will accept it.

Thanks.