Bergeon 6 ATM Waterproof Tester Bergeon 6 ATM Waterproof Tester is an apparatus for testing the water resistance of watch cases. This Bergeon 5555/98 Waterproof Tester tests up to 6 Atmospheres (1 ATM = 10 meters). The advantage of using a water type tester is that when pressure is released and the watch is plunged into the water, bubbles of air exiting the case will pinpoint where the case is leaking. Distilled water is placed in the cylinder, aprox. half full. Watch is suspended above the water and the air pressure is increased using the built in manual pump. If the watch case leaks, the increased air pressure will seep into the watch case. Press the air release valve and plunge the watch into the water. The air which leaked into the case under pressure will now exit the case, providing a visual indicator of the leak source. Make sure to remove the watch from the water before the pressure equalizes, to insure that no water enters the watch. It is extremely important that you Distilled Water, distilled water will prolong the life of this tester. It is also extremely important to regularly grease the O-ring gaskets of your tester using Silicon 7. An instruction booklet is included with the machine indicating both how to use the machine as well as proper maintenance.