BJ Enterprises Sentry-Jarhead Tank Monitor combines a wall-mounted Sentry tank alarm with a Jarhead tank gauge to provide audible and visual warning of a low or high tank level. The 2-piece Sentry unit indicates a low or high tank by sounding a 103-decibel siren, with a control panel that can be mounted almost anywhere for easier accessibility, while the sight glass of the Jarhead tank gauge visually indicates contents in 1/4-tank increments with an orange indicator and a nitrophyl float. When activated to an alarm condition, the Sentry will sound its built-in siren for as long as it is connected to a power source, operating on AC power with a 12 volt transformer, and it is engineered for use on most single- and double-walled above-ground tanks. A low-cost unit that is simple to install and easily maintained on-site, the Sentry also features weather-resitant housings for all its buttons, a UL buna sensor, and a 1/2" x 6' pipe that is easily field adjustable to provide a tank depth from 2" to 10', and the large, 4-window display of the Jarhead is highly visible and easily read from any direction. Tank depth must be specified from 18" to 72" when ordered, and this unit can not be used to run accessories.