A mobile water analyzing system for determining an analyte in a water sample includes a basic unit and a test element configured to be inserted into the basic unit. The test element includes a sample line with an inlet opening configured to receive the water sample, a measuring section forming a measuring track and configured to allow the determination of an analyte, a pump opening, and a key reagent disposed inside the sample line. The basic unit includes a test element receptacle configured to hold the inserted test element, an analyzer with an analyzer measuring track formed by the measuring section, and a pump actuator cooperatively connected with the pump opening.