BJ Enterprises Sentry Leak-Guard Tank Alarm combines a wall-mounted, battery-operated Sentry tank alarm with a Leak Guard tank gauge to provide audible and visual warning of an interstitial leak. The Leak Guard is a large, visual sight gauge that will indicate with a highly-visible orange indicator if a leak occurs in the interstitial space of a double-wall tank, with a 4-window glass display that is easily read from any direction, while the 2-piece Sentry unit indicates a leak by sounding a 103-decibel siren, with a control panel that can be mounted almost anywhere for easier accessibility. When activated to an alarm condition, the Sentry will sound its built-in siren for up to 4 days on a fresh 9-volt battery, and the Leak Guard unit comes with a nickel-plated brass chain that is field-adjustable to 72 in depth.