A transient test-based technique for leak detection in outfall pipes

A technique is proposed for leak detection and evaluation in outfall pipes based on properties of transient pressure waves. Transients are caused by an increase of the piezometric head at the initial section of the outfall pipe. Since high overpressures are not necessary for the success of the technique and simple equipment is required, tests may be repeated periodically to check the state of the pipe. In order to verify the possibility of locating a possible leak on the basis of the results of transient tests, the effects of a leak on wave propagation from the numerical point of view are discussed first. A first-order formula for preliminary evaluation of the discharge behavior of the leak is also given. Results of some laboratory tests carried out on a long pipe are shown in order to confirm the reliability and validity of the proposed technique. Inverse transient calculations are proved to be able to provide precise information about the characteristics of the leak.