I recently added a 8th zone for drip irrigation to my sprinkler system. The drip system has 3/4" pipe with a 30 psi pressure regulator and about 25 emitters taped into the 3/4" pipe. Some of the 3/4" pipe goes uphill. The problem that i noticed is when i turn on the drip zone, the back flow preventor seems to be hammering or vibrating. The flow to the emitters is very low but that is intended to do a longer slow soaking for the flowers and roses. I read someplace that the back-flow preventor could be getting messed up because there is not enough flow. Anyone have any idea what the issue is and how i can fix it?