I have three nipples hooked to a pipe, which is gravity fed from a 5 gallon bucket - pretty typical setup. No water hose or active water supply other than the bucket.
I too have been looking at the 4090 pressure regulator, because all three nipples leak! Yes, just from the simple gravity feed. I noticed they leak more when the bucket is full, and less when it runs empty. These nipples did not leak AT ALL when they were attached to the bottom of quart jars, so I'm pretty sure this is pressure.
So now, like you all I am thinking about sinking more money into the system to get the regulator. After $200 on the coop - I'm ready to stop spending money! but I hate the wetness a lot.
So - been trying to read and see if this regulator will help stop drips.