A well cap assembly is disclosed which is well suited for use with a wellhead. The well cap assembly has a port component and a cap element. The port component has a bore extending therethrough, an upper neck portion, and an upper threaded portion. The port component further has a lower threaded portion and a barb formed on the upper neck portion. The barb can receive an external flexible tube which is temporarily secured to the port component. The cap element has an internally threaded portion which engages with the upper threaded portion of the upper neck portion and seals the bore of the port component. The cap element also has a tether for securing it to the port component.