This paper concerns the monitoring of water ultra-filtration devices by vibration analysis. Damaged devices are characterized by the presence of air bubbles that can be heard by a trained service engineer. The present study investigates the feasibility of an automated detector that could complete the engineer's expertness. A description of the filtration devices is given and the main features of the transients to be detected and the ambient noise are brought to light. Based on these features, six detectors are proposed. They are tested and compared through Monte Carlo simulations over data built from real life signals.