Ahm semi-re-plumbing the lines to the HW heater, and I noticed what appears to be some sort of vent/pressure relief ditty coming off the *CW inlet to the HWH*. From the CW pipe to this gadget is copper, from the gadget to the wall is 1/2 black pipe. The 1/2 pipe goes thru an outside wall, altho I have yet to find anything outside!
I'd be hardpressed to imagine that this thing still works, whatever it was. I'm sure it's 25++ years old. It's not an anti-water hammering device, afaict. Is it safe to just get rid of this thing? City water pressure is barely 60 psi, I have gauges plumbed into a couple of lines, very little variation. It would make my life a lot easier if I could ignore/get rid of this thing.