2 cut-off valves?

I've got a problem with the the irrigation system for a house I bought recently. It is original to the house (1967) and galvanized steel.

There are four zones. The two in the front yard work fine but the two in the back aren't working. I removed the bleed screws from the valves in the back yard and apparently there is no water getting to them. There is a cut-off valve in the front yard....is it typical to have another for the backyard?

There are two backflow preventers sticking out of the ground, front and back. Does that indicate that there is a second cut-off valve? If so, is there a logical place for me to start looking for it?

thanks for any help

Being an old system like that, anything is possible. They make zone valve finders, but I don't think they'll find a shut-off valve that has no wires running to it.

If you don't have a blue print of your irrigation layout, about all you can do is poke in the grass with a long screwdriver in the areas you believe to be the most "upstream" from the rear zones.

I'd start poking around near the backflow preventer in the back.

Is there water at the Back Flow for the rear yard?

Do the valve control wires follow the main line from the Back Flow?

I opened the cap on top of the backflow preventer and can see water on the inlet side. I also put a hose in the outlet side to see if there was a block between the backflow preventer and the valves....there wasn't.

The controller wires are buried along the base of the house. The backflow preventer is up a small incline about 20 feet from the house/valves.

The shut-off for the front is attached to the backflow preventer, so that was the first place I looked in the back. I dug around the backflow preventer and followed the main line for about 5 feet and didn't see anything.

Can you post a picture of the backflow in the backyard? I guess I don't understand what you meant by you could see water on the inlet side.