Alde Gas Leak Detectors Alde gas leak detectors, aka Alde bubble leak testers, should be installed on any LPG system. Press the red cap 1–8 minutes and watch the glycol fluid inside the glass chamber. If there is a leak in the system, the fluctuating gas pressure will create bubbles in the fluid. Alde gas leak detectors should be installed inline, as near to the regulator as possible and before any appliances. They come with ø8 and ø10 mm connectors.