Ours are on a timer to blow off a small amount of air at a few low spots in the system every five minutes, even though having a refrigeratant type demudifier.

Ours are on a timer to blow off a small amount of air at a few low spots in the system every five minutes, even though having a refrigeratant type demudifier. One of the devices stopped working between services and the bottom reciever tank half filled with water. Edit: they're call bleed valves