How Are Watches Water-Pressure Tested?

Many people have asked us, how are watches water pressure tested?

For water pressure testing our watches, we use the special machines that can waterproof test a watch without getting it wet. We use the Witschi ALC2000 tester. This machine uses compressed air and an extremely sensitive sensor to measure minute fluctuations in the watch’s size under high pressure, which will tell us whether a watch is water-tight.

We use this test any time we open a watch, for initial assembly or after-sales service. It is a quick and reliable way for us to know that your watch is waterproof when it leaves our Service Center.

The first step is to place the watch in the testing machine and lower the sensor onto the crystal of the watch: when the sensor light turns on, this indicates that the sensor is correctly aligned and ready. We then close the chamber and start the test. A compressor pumps compressed air into the chamber.

Next, The high pressure will begin to “squeeze” the watch, compressing it very slightly. Once the chamber reaches the set pressure and the watch stabilizes in its compressed state, the test begins.

If the watch is completely water-tight, the watch will remain compressed for the programmed test period. The watch will experience no re-expansion until the test is over. If the watch passes the test, a green light comes on to indicate that the watch is watertight.

If there is a leak anywhere, this will allow the high pressure air in the chamber to seep into the watch. As the pressure inside and outside the watches equalizes, the watch re-expands to its original shape and this expansion is detected by the sensor. This causes a red “fail” light to come on and tells us that the watch is not watertight.

On a ruggedly built watch, the steel or titanium and crystal will only be compressed very slightly, even under high pressure, so the sensors in these machines need to be extremely sensitive. They can detect expansion or contraction of the case down to tiny fractions of a millimeter, which is why the machines are so expensive. The big advantage is that they allow us to know with great reliability that your watch is truly water-tight before it leaves our Service Centre.

And that is how we water-pressure test all of our watches! Most Momentum watches feature a screw-down crown: after any adjustment, please always remember to screw the crown firmly into the case before you get your watch wet!