I recently moved into a new house. I was trying to test out the sprinkler system. I turned on the sprinkler valve in the utility room. I also turned on the valve on the backflow device (I think - never done this before). When they are both open the backflow device sprays water everywhere. In the video below I have it only slightly turned on so the spray is much less than full blast.
Am I opening the valves incorrectly? Is the backflow device broken? Or is it something else?
Video of issue: https://youtu.be/FHcr1fxBZqk