I got a call this morning from my cleanup guy. He said that the backflow preventer was spewing water from the vent. The backflow unit is a Wilkins 975XL. When I got there sure enough water was pouring out of the vent. I turned the power off to the bays and turned off the water to the car wash. When I removed the #1 and #2 check valves, I found a small piece a plastic on the face of the #1 check valve. I remove the piece of plastic and turned the check valve diaphragm over. Reassembled the check and turned the water and power back on, no leaks all is good. It took all of about 10 minutes.