MrFixit,
Believe it or not, that is exactly what I did after I posted. I thought it had to be a leak because of the low pressure.
I first wiggled each riser, then dug down a bit to see, figuring that in the past whenever I had a break, it was close to a riser. This time no breaks were found. I then capped off each riser with 3/4" female caps. I then turned the zone back on.
All of a sudden, in a place I did not think there were any pipes, I had a bubbling up of water, like Niagara Falls...!
I found the break. Actually, about a foot of pipe was snapped off, and I have NO IDEA where it went. You could tell it had been this way for a long time. I just repaired it, and will turn it back on and test tomorrow.
I learned some good stuff from you good people this time. A pressure gauge is a great tool to diagnose. Wet Boots was correct...it's a good tool to own. I did not understand how it would help at first, but then it all fell into place and I understood.
Again, thank you all for your good help. I enjoy learning about sprinkler systems, first, because I now own one, and second, there are many senior citizens in my neighborhood down here who can't seem to get anyone to help them with sprinkler problems. The more I learn the more I can help them.
thanks, Frank D.
"He is no fool who gives up what he cannot keep to gain what he cannot lose"