air tap

air vent

In a water distribution system, a vent for releasing trapped air; usually located at the highest point in the system.
References in periodicals archive ?
He was forced to run a cleaning rod from the muzzle through the air tap and into the transfer port, then hammer the rod until two lead plugs fell out the back of the gun.
In particular, males slowly followed a dragline, tapped and/or plucked it with their palps, and performed leg I raises and extensions with air taps.