Acoustic leak monitors in mechanical contact with components of special interest have clear advantages over many alternatives, in particular for continuous monitoring over time or during specific operations. Non-invasiveness and repeatability are among the most important benefits of this technology. In connection with a delivery of self-contained, battery operated subsea leak monitors, the technology was demonstrated in a laboratory environment. A 20″ subsea valve was fitted with acoustic leak monitors, pressure sensors and a mass flow meter. Artificial damages were made to the valve in three incremental steps. One port was pressurized with nitrogen, and the resulting leakage flow was detected and quantified. Detection thresholds as low as 1 SCM/h were observed in the demonstration. Higher thresholds are however predicted for most field situations.