I'm relatively new to the world of backflows having just completed my tester certification course last year. I have a 1/2" Watts 009QT RP assembly that is spraying water from the little nipple in the middle of the top cap above the relief valve piston. I opened it up, found a broken piston O-ring (the red one that goes on the plastic piston itself). I replaced that O-ring but it still sprayed water. I then bought a relief valve rebuild kit and installed it but the same thing is happening. Is the little nipple on the top of the cap supposed to be open (air vent, etc)? If so what seals it so it doesn't spray water? There's also a slight dent in the cap below one of the 4 slots at the bottom of the cap (I have no idea how that happened). Could that be causing the leak? I tested this device 4 months ago and it tested ok. Help!