How is the water resistance of a watch measured?

When buying a watch, there is a criterion that must be taken into account: the water pressure resistance, more commonly known as "sealing".  This is essential data to know if you can put your watch in contact with water and above all, at what level of pressure. So you know, in watchmaking nothing is so simple, so there are a few subtleties to take into account. Rest assured, you should quickly understand, 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). It is the most common unit of measurement although some brands use meters (m) or feet (ft). ATM is a unit measuring the pressure of the atmosphere that a watch and its mechanism can withstand. More concretely, 1 ATM is equivalent to 1 bar and therefore 10 meters depression. It is also the value of the atmospheric pressure of the Earth at sea level. So you can imagine, a 1 ATM watch is not absolutely not waterproof. Also, if your watch does not show 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 to talk about a waterproof watch is 3 ATM (30 meters). But then does that mean that if I dive more than 30 meters deep, my watch will no longer work? Well no, imagine that you can't dive at all with such a watch. Remember, ATMs measure the pressure what your timepiece can withstand. However, a few drops of water can already, on their own, reach a level of pressure higher than what you imagine.  

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

The different sealing levels

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

3 ATM water resistant watch (30 meters)

As stated above, this is the smallest level, and therefore the most restrictive at water level. Indeed, a 3 ATM watch does not resist no immersion in the water, it would be fatal to him. This degree of tightness is only resistant to splash occasional such as: hand washing or rain.

5 ATM water resistant watch (50 meters)

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

10 ATM water resistant watch (100 meters)

A watch of this level of water resistance allows all kinds of water exposure, well almost. Of course, it resists swimming, sports swimming, diving and even the practice of diving with a mask and snorkel. However, excessively deep immersions such as when practicing scuba diving are not recommended.

20 ATM water resistant watch (200 meters)

From this level you can enjoy your watch in complete peace of mind. Your timepiece can withstand all immersions, even deeper. When this level of water resistance is reached, we generally speak of a watch. "diver". So don't panic she 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 that there are watches even more waterproof than 20 ATM. For sports watches or specially designed for the practice of professional diving, one can encounter a level of tightness of up to 200 ATM (yes it corresponds to 2 meters).

Caring for a waterproof watch

Using your watch in relation to its level of water resistance is necessary to keep it functional. However, there is a criterion to which attention must be paid to take even more care of it: the 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 well screwed 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 Thermal shock to your timepiece. Exposing your watch to the sun or strong heat and then bathing it in cold water may be one of the reasons causing condensation. 

In any case, be reassured, condensation inside a watch is neither rare nor serious. To solve the problem, it is usually sufficient to leave your watch dry and in a rather warm place, allowing the mist to 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 put your watch under freshwater. This eliminates 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 wear out over time. Every 3-4 years depending on the model we recommend doing revise your timepiece with watchmaking professionals. 

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