An end-of-zone or line sensor placed at the end of a secondarily contained fuel piping(s) or network(s). The interstitial space of the piping network is coupled to a vacuum-generating source that draws a vacuum level in the interstitial space to monitor for leaks or breaches in the piping network. The end-of-zone sensors are coupled to the interstitial space at the far end of the piping network and vacuum-generating source. The end-of-zone sensors actuate when a sufficient vacuum level is detected. A control system monitors the status of the end-of-zone switches. If the vacuum-generating source is activated to draw a vacuum level, and the end-of-zone sensors react to indicate the vacuum level has reached the sensor, the control system knows that there is no blockage over the entire span of the piping network, and thus entire piping network can be properly monitored for leaks.