The invention relates to a method for detecting and/or quantifying water leaks in a water pipe, and to a device for realizing said method. The method of the invention comprises measuring the water flow rate in the pipe in at least two different locations, i.e., one downstream and one upstream relative to the suspected leak, the water flow rate being measured by injecting a tracing agent that modifies the water conductivity instantaneously at an upstream location and a downstream location relative to the suspected leak location, continuously measuring the water conductivity downstream from said locations and, from the conductivity values, calculating the water flow rates upstream and downstream relative to the suspected leak location in the pipe. The method of the invention can be used for quantifying a leak flow rate that can even be a very small one.