How to Pressure test a watch
Before testing the watch there is a bit of preparation.
- Look for obvious reasons why the watch may not be waterproof like broken glass, faulty crown, cracked case or a loose back.
- Look for signs of previous water damage. If water has been in a watch before you really don’t want to be guaranteeing it waterproof.
- Change the battery
- Double check the seals are OK. It is even worthwhile removing the crown and stem and checking that seal.
Once you think that the watch will pass the test and will not need further work in the near future, proceed with the pressure test.
- The watch is placed in the air above the water and then put under pressure. I use 3 bar on most watches or 5-7 bar for watches that are going to be used for diving.
- Wait 15 mins
- If the watch is leaking then air will leak into the watch.
- Reduce the pressure slightly.
- Lower the watch into the water
- Reduce the pressure slowly while checking all joints where the watch may leak
- The watch (if it is leaking) will have a stream of bubbles where the leak is.
- If it is leaking REMOVE THE WATCH FROM THE WATER IMMEDIATELY. Slowly, very slowly, reduce the pressure.
This test can go wrong, sometimes spectacularly. Here are what to look out for.
The watch exploding: Yes this can happen. Usually when the watch has a slow leak which you do not spot so the pressure difference between inside the watch and outside is to much and the glass pops off Filling the watch up with water. This is why you never do the test in front of a customer
Air/Water Leaks in but not out: this generally happens on watches with a screw crown and it is hard to spot
Sometimes you just cant tell: Watches with many air voids in the casing can hide a leak (especially Casio G-Shock). There are just so many bubbles you just cant tell.
A Leak at low Pressure: If the back does not fit well or a seal is too small the pressure at 3 bar seals the watch and you think the watch is waterproof when it isn’t
Misting of the glass: Sometimes a watch can look like it has let water in and it hasn’t. there are 2 main types of misting.
1): The glass can “steam up” with humidity in the air. Hot humid air gets in the watch then when the weather cools down water is deposited on the glass (as its the coolest surface)
2): The oils (I think) evaporate and deposit themselves on the glass.
The humidity is important to remove as it is water and does rust parts it may come in contact with
Static Test Isn’t the real world: The watch is stationary in the pressure tester and this is not how the watch will be used. Moving, knocking, and touching pushers and crowns can not be tested. Changes in temperature also affect the water resistance. A sudden change from the heat of a sunny beach to a cold sea can make a normally waterproof watch leak. You can’t test any of these scenarios.
Waterproof Today Leaking Tomorrow: a seal can fail this fast. Change the time or date, press a button or knock the watch and it could fail. Water is a powerful enemy and sneaks in through the smallest gap.