Hi, I purchased a pressure regulator and lately I have noticed that the irrigation connected to it has very little pressure. I then take off the filter cap, shake out the filter and discover little to no sand / debris in the filter. I screw the filter cap back on, and walla, the pressure is fine again. But there was no debris that I am clearing.

It seems that the only trick to get my pressure working again is to remove and screw back on the filter cap. Is this a vacuum issue or something? Something to do with another part of the pressure regulator? Help, RainBird won't tell me what is wrong!