Advance Flow Diagnostics (AFD patent pending)- AFD is a real time application in which product is monitored as it is withdrawn from the tank and includes a processor which is also recording the associated valid fuel transactions which are being recorded through the dispensers. Typically, the system is equipped with control devices which are capable of shutting down fuel systems and sounding an alarm when dispenser theft is occurring. The system is also capable of identifying emergent catastrophic leaks in lines and shutting down the associated pump. Unlike other forms of catastrophic leak detection (as specified by the EPA) the system is capable of identifying line leaks while the dispensing systems are in operation. Conventional catastrophic leak detection systems are only capable of detecting large leaks when all dispenser systems are idle. Since the EPA is slated to specify that active facilities will need to accomplish a catastrophic leak test once per hour, the AFD system will allow a facility to operate without shutdown or disruption to achieve the once hourly test.