Everything you need to know about waterproof watches

Waterproof watches: everything you need to know about waterproof watches

Technical guide

Have you often wondered about the terms watertight, waterproof or water-resistant on the back of watches? Do you own a watch marked "water-resistant 30 m" and wonder if you can really dive to a depth of 30 metres? Would you like to know how to protect and maintain your water-resistant watch?


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Bars, atmospheres, metres... How is the water-resistance of a watch measured? What makes a watch water-resistant more or less? How can manufacturers of water-resistant watches like Pierre Lannier test and guarantee the water-resistance of their watches?


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"Watertight" in its general sense refers to the characteristic that does not allow liquids or gases to pass through. In watchmaking in particular, the water-resistance of a watch refers to its resistance to pressure: that of water, and therefore its resistance to water penetration. The French term "étanche" and the English term "water-resistant" are both used interchangeably and correspond to criteria defined by international standards: the ISO-2281 standard for so-called "water-resistant" watches and the ISO-6425 standard for so-called "diving" watches.

These terms are always accompanied by a measurement indicated in bars, metres or atmospheres (atm), for example water-resistant 50 metres, water-resistant 5 ATM, water-resistance 5 bar, etc. Other terms that appear on the cases of certain brands, such as "waterproof" or "water-resist", are not covered by any standard and are therefore unreliable. A diver's watch must be water-resistant to 100 metres or more and is subject to a different standard with more stringent criteria than a water-resistant watch intended for everyday use. The water-resistance of a Pierre Lannier watch is measured in metres; you can thus read on the back of your Pierre Lannier watch: 30m water-resistant, 50m water-resistant or 100m water-resistant.

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Ensuring the water-resistance of a watch is a delicate task! Indeed, it is inevitable that the case has openings to allow the passage of the winder and pushers if necessary. Water-resistance is ensured by suitable seals which ensure the solidarity of the different parts of your water-resistant watch.

However, all the elements that make it up guarantee the water-resistance of a watch. A stainless steel case is essential, ideally with a screwed back, as well as a resistant glass, sufficiently thick and fixed to the case by a water-resistant material.

In addition, some models of water-resistant watches, especially diving watches, have a screw-down crown that ensures greater resistance to water pressure. Obviously, all these components must be in perfect condition to offer the greatest water-resistance.

This is why your Pierre Lannier watchmaker pays particular attention to his water-resistant watch models. Individually tested, they are all checked in order to offer you the greatest satisfaction. Pierre Lannier guarantees a water-resistance of at least 3 ATM on each of its watches, which will allow you to use your watch without fear of damaging it while washing the dishes or taking a shower, for example.

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The ISO-2281 standard, introduced in 1990, specifies the criteria for determining water-resistance and the tests to which a watch is subjected in order to be able to display the words "water-resistant watch" or "waterproof watch". These tests verify the resistance of the watch after assembly based on pressure, immersion time and temperature criteria. They consist, for example, of one hour's immersion in 10 cm of water at a temperature of 18°C to 25°C, short immersions in water at different temperatures, exposure to overpressure of water and then air, etc. To be able to display the indication "water-resistant watch" or "water-resistant watch", the watch must show no sign of water penetration or condensation inside the glass after each of these tests.

As mentioned above, water-resistance can be expressed in different ways: atm, bar or meters. When the water-resistance of a watch is specified in the form of a depth: "water-resistant 30m", "water-resistant 50m", "water-resistant 100m", this does not correspond to a depth at which you can take it underwater!

Indeed, to the static pressure exerted by the water at a certain depth is added the dynamic pressure created by your movement and that of your wrist under water. To sum up, a watch marked "water-resistant 30m" means that your watch can withstand the pressure exerted by water at a depth of 30 metres.

As you have understood, the water-resistance of a watch depends on many criteria that watch brands must apply to certify that it is "water-resistant". Pierre Lannier, which has always been committed to making quality watches and satisfying the greatest number of people, offers watches whose water-resistance allows you to swim and bathe with your watch, always at affordable prices.