A storage tank leak detection and prevention system that detects a breach or leak in the interstitial space of a double-walled fuel storage tank (101) in a service station environment. The interstitial space is placed under a vacuum using a submersible turbine pump (15) that is also used to pump fuel to the fuel dispensers in the service station and therefore a separate vacuum generating source is not required. A sensing (46) unit and/or tank monitor (42) monitors the vacuum level in the interstitial space over time. If a significant vacuum level change occurs in the interstitial space after the interstitial space is placed under a vacuum level, a catastrophic leak detection alarm is generated. If a minor vacuum level change occurs in the interstitial space after the interstitial space is placed under a vacuum, a precision leak detection alarm is generated. Functional tests also ensure that the leak detection system is functioning properly.