Many times properties have PVB / Backflow for the irrigation system and sometimes for other things. They might look like the ones in the photos below. They may have a copper colored top instead of a black one like these. Often times we see them located in homes front or the side yards Many times turning the PVB off will stop water from leaking turning what would have been an emergency or after hours call into a scheduled service call. Never force knobs and make sure it is only for the irrigation.
The one in the photo to the right is in the "on"position. Notice that there is black tape on some of the pipes but the PVB itself is not insulated. Many times there is water in the PVB and weather can cause the water to freeze and break the PVB. When PVBs break or leak On Time Landscaping can usually replace them.
Many times but not every time; when handles do not go in the same direction as the pipe they are on they can be in the off position.