Odd valve on cold supply

sorry i dont have pictures here, but i saw a device i was not familiar with yesterday. a small pear shaped valve thingie on the cold supply (nowhere near the meter) it was instaled off a “T” below a gate valve?? (OOPS, this should be in plumbing!!)



Sounds like a pressure regulator.

not a pressure regulator, although shaped like one.

this thing was in the middle of the line and had no means of adjustment. with the valve right there the only thing that i thought could be some kind of flush out???