A device for accumulating, isolating, indicating and venting accumulated gas in a fluid system pipe includes a main pipe fitting affixed to a system pipe in which a hole has been drilled. A standpipe attached to the pipe fitting houses a magnetic float. A magnetic-float level indicator exterior to the pipe indicates the magnetic float's level. A valve attached to the standpipe above the magnetic float allows controlled ventilation of the gas in the standpipe and thus in the piping system. Gas from the system pipe accumulates in the standpipe, removed from the primary fluid flow path of the system pipe. In the standpipe, as the liquid/gas interface drops, the float drops to a pre-determined level, at which point the user vents the gas from the piping system, causing the magnetic float to rise indicating that gas is again at acceptable levels in the piping system.