How is the water resistance of a watch measured?

When buying a watch, there is one criterion that must be taken into account: resistance to water pressure , more commonly called " waterproofness ". This is essential information to know if you can put your watch in contact with water and, above all, at what level of pressure. As you know, in watchmaking nothing is so simple, so there are a few subtleties to take into account. Rest assured, you should understand quickly, GUSTAVE & cie is here to make you a real expert in the field.

Understanding the water resistance of a watch

In watchmaking, the water resistance of a watch is measured in ATM (abbreviation of Normal Atmosphere). This is the most common unit of measurement, although some brands use meters (m) or feet (ft). ATM is a unit measuring the atmospheric pressure that a watch and its mechanism can withstand. More specifically, 1 ATM is equivalent to 1 bar and therefore 10 meters of pressure. It is also the value of the Earth's atmospheric pressure at sea level. So, as you might expect, a 1 ATM watch is absolutely not waterproof. Also, if your watch does not have any indication of its water resistance, it is simply not waterproof, so keep it away from all sources of water.

In the world of watchmaking, the bare minimum for a watch to be waterproof is 3 ATM (30 meters). But does that mean that if I dive to a depth of more than 30 meters, my watch will no longer work? Well no, imagine that you cannot dive at all with such a watch. Remember, ATM measures the pressure that your timepiece can withstand. However, a few drops of water can already, on their own, reach a higher pressure level than you imagine.

From 3 ATM to 20 ATM, there are several levels of water resistance corresponding to different uses of your watch. To find out if your timepiece is just water resistant or waterproof, let's look at the different levels of water resistance.

The different sealing levels

These famous water resistance levels tell you under what conditions your watch can be in contact with water and what activities are possible with your watch on your wrist. Here is a list of the different levels you may encounter when purchasing your watch.

Waterproof watch 3 ATM (30 meters)

As stated above, this is the smallest level, and therefore the most restrictive in terms of water. Indeed, a 3 ATM watch cannot withstand any immersion in water, it would be fatal. This degree of water resistance only withstands occasional splashes such as: hand washing or rain.

5 ATM (50 meters) waterproof watch

A watch indicating 5 ATM allows a little more exposure to water but you must remain vigilant for the sake of its mechanism. It will be suitable for rather calm immersions such as a bath, a shower or swimming without diving. However, we insist on the term "calm". Exposing your watch directly under a jet of water or making too many movements in the water could make it defective. The force that a jet or movement can generate is precisely what exerts pressure on your watch, so be careful! When purchasing in store, we advise our customers not to stay underwater for long with a 5 ATM watch. Limit swimming but know that if you forget to remove it before showering, it will not be a problem!

Waterproof watch 10 ATM (100 meters)

A watch with this level of waterproofing allows all kinds of exposure to water , well almost. Of course, it is resistant to swimming, competitive swimming, diving and even snorkeling. However, diving too deep, such as when scuba diving, is not recommended.

Waterproof watch 20 ATM (200 meters)

From this level you can enjoy your watch with complete peace of mind. Your timepiece can withstand all immersions, even the deepest. When we reach this level of water resistance, we generally speak of a "diver" watch. So don't panic, it is made for water and water sports such as surfing or jet-skiing.

Are there higher levels?

Indeed, if we ask the question, it is because there are watches that are even more waterproof than 20 ATM. For sports watches or watches designed specifically for professional diving, we can find a level of waterproofing of up to 200 ATM (yes, this corresponds to 2,000 meters).

Caring for a waterproof watch

Using your watch according to its level of waterproofness is necessary to keep it functional. However, there is one criterion that you must pay attention to in order to take even more care of it: condensation . This phenomenon results in fogging inside your glass or even small droplets. To avoid this, it is recommended to check that the crown used to wind the movement is properly screwed in before going into the water. This type of crown, specific to waterproof watches, prevents water from entering the mechanism. If ever a drop manages to find its way into your watch, it can create condensation, or even worse, seriously damage the movement.

Also, it is recommended not to subject your timepiece to thermal shock . Exposing your watch to the sun or high temperatures and then bathing with it in cold water may be one of the reasons causing condensation.

In any case, rest assured, condensation inside a watch is neither a rare nor serious phenomenon. To solve the problem, it is generally enough to leave your watch dry and in a rather warm place, letting the condensation evaporate. However, if this phenomenon is recurrent, it is advisable to go to your watchmaker.

After swimming in the sea, it is also recommended to rinse your watch under fresh water. This will remove any salt and sand deposits that may have remained on the glass or case, thus avoiding any risk of micro-scratches.

Finally, be aware that a watch is a fragile object and that its water resistance can be depleted over time. Every 3-4 years depending on the model, we recommend having your timepiece serviced by watchmaking professionals.

Conclusion

Finally, the most important thing is to keep in mind the future use of your watch to choose one that is more or less waterproof. The water resistance of a watch should no longer hold any secrets for you, so take the plunge and visit your watchmaker!