Abstract: The invention relates to a leak control system (1) in two-stringed pipe installations and a method of executing a leak control system comprising one stop valve (2) with an associated flow meter (3) arranged in the supply pipe (4) of the pipe installation, and one stop valve (5) with an associated flow meter (6) arranged in the return pipe (7) of the pipe installation, said stop valves (2,5) as well as associated flow meters (3, 6) being connected to a control box (8), said box (8) comprising one valve monitor (9) connected to each stop valve (2, 5) to control/record the possible state of the individual stop valve (2, 5): open or closed, as well as an executer which, in combination with the control logics of the control box and the operating conditions of the pipe installation, controls/monitors the valve monitors (9) during a given sequence of actions, said leak control system (1) being capable of performing a number of measurements and data collections to evaluate the functionality of the stop valves (2, 5)