Why is water resistance important in watches?

Whether you're showering, washing your hands, bathing or swimming, you don't have to be a diver for the watch you're wearing on your wrist to come into contact with water. Because it's extremely impractical to constantly take your watch off in everyday life to avoid getting splashed with water, many watch wearers choose a model that is water-resistant to a certain degree. Waterproof wristwatches have the advantage that their movement is protected against the pressure at a certain water depth and no water can penetrate the case. The information on water resistance tells you up to what depth this is the case for each model. This article looks at the technical background and standards for the water resistance of watches and gives tips on buying waterproof timepieces.

The most important things in brief

• Meaning of 10 ATM: A watch that is water resistant to 10 ATM can withstand a water pressure of 10 bar, as experienced under test conditions at a depth of 100 meters.

• Suitability: Such a watch can be worn while washing hands, showering, bathing, swimming and snorkeling, but not while diving.

• Care and maintenance: To keep a watch water-resistant for as long as possible, it should be cleaned after intensive contact with water. It is also advisable to check the seals regularly.

What does "waterproof up to 10 ATM" mean?

Watch manufacturers usually use the units meter, bar or ATM to indicate the water resistance of a product. A value in meters tells you directly up to what depth a watch can withstand water pressure. Bar refers to the prevailing hydrostatic pressure under water. If a watch is 10 meters below the water surface, an excess pressure of 1 bar can be expected.

The abbreviation ATM stands for atmosphere and also refers to the pressure resistance of the watch, namely at a still water surface. 1 ATM corresponds to the pressure that prevails at a depth of 10 meters, so 10 ATM would stand for 100 meters. 1 ATM is not quite the same as 1 bar, since 1 atmosphere is strictly speaking converted to 1.01325 bar, but for the sake of simplicity the values ​​are usually used in an adjusted manner. So we can remember: 10 meters of water column = 1 bar = 1 ATM. This means:

• 20 meters = 2 bar = 2 ATM

• 30 meters = 3 bar = 3 ATM

• 50 meters = 5 bar = 5 ATM

• 100 meters = 10 bar = 10 ATM

Technical Basics of Waterproofing

If we delve a little deeper into the background of water resistance in relation to watches, we quickly come across the physical concept of pressure under water. When the water surface is at rest, there are no pressure peaks - such as those that occur when diving into water after jumping from a 5-meter tower - and there are no major temperature fluctuations, the water pressure acting on the watch increases by 1 bar or 1 ATM every 10 meters. In order to produce a waterproof watch, various precautions must be taken and elements integrated into the design to ensure that no water penetrates the case despite the pressure. Built-in seals, a firmly screwed case back and screwed crowns with sealing rings are common.

Categories and standards of water resistance

How waterproof a watch is is tested using a standardized test procedure. Special testing equipment subjects the timepieces to a test pressure (air pressure) in the laboratory. The test results are interpreted according to the applicable DIN standards:

• From 2 bar or 2 ATM: The watch is splash-proof ("water resistant") and can be worn while washing hands or in light rain, for example

• From 5 bar or 5 ATM: The watch can be taken into the shower without any worries

• From 10 bar or 10 ATM: The timepiece can be worn in the swimming pool and for snorkeling

• From 20 bar or 20 ATM: The watch is suitable for free diving or scuba diving at shallow depths

Many diving watches offer much more: although they "only" have to be waterproof up to 20 atmospheres according to the DIN 8306 standard to be able to bear the name diving watch, in many cases they can withstand 30 ATM and more. Then adventures at greater diving depths are no problem.

Practical applications and activities

In summary, this means that a waterproof watch with an ATM rating of 10 can withstand everyday stresses associated with water. Neither showering, bathing, washing hands or swimming will damage the watch. If you are specifically looking for watches that are suitable for water sports at shallow depths, such as snorkeling, 10 ATM is theoretically sufficient, but free divers and scuba divers should opt for a model that offers its movement sufficient protection up to at least 20 ATM. As already mentioned, manufacturers can call their watches diving watches if they are not only water-resistant but also "submersible", which according to the standard is the case from 20 ATM.

Care and maintenance of waterproof watches

Both splash-proof watches and diving watches must be properly maintained and cared for to ensure they remain waterproof for as long as possible. After contact with water, the watches should be cleaned superficially and the seals checked to ensure they are working properly. Chemical cleaning agents, which include many household cleaners, should be avoided as these can attack the seal material and cause serious damage. If the inspection reveals that there is already obvious damage, the watch should be taken straight to a specialist for servicing. Professional servicing at regular intervals is generally recommended.

Despite the best care, a waterproof watch does not usually remain waterproof forever. The water resistance decreases over time with use, so that, for example, a watch that was waterproof up to 10 ATM when it was first bought may only be waterproof up to 5 ATM over the years. If you wear older watches, you should keep this in mind.

Buying advice: What should you look for when buying a waterproof watch?

If you want to buy a waterproof watch, you should first and foremost consider these criteria when buying:

• Water resistance level: What information does the manufacturer provide regarding water resistance (information in meters or bar or ATM)?

• Area of ​​application: For what purpose is the watch purchased (e.g. everyday companion, for swimming or diving)?

• Quality and case: How high quality should the watch be and which materials are preferred for the case?

• Bracelet: Depending on the application, the bracelet should be made of a material that does not soften or fade even when in intensive contact with water.

For beginners who are satisfied with splash protection, the Royal Oak from Audemars Piguet, which is water-resistant up to 5 ATM or 5 bar, is a good option. Advanced, price-conscious hobby snorkelers might choose the Seiko 5 Sports , for example, while water sports enthusiasts with a more generous budget opt ​​for the Rolex Yachtmaster, which is also water-resistant up to 10 ATM. Anyone looking for a reliable companion in greater water depths should take a look at the robust Seamaster Diver 300 or the Seamaster Planet Ocean 6000M from Omega.

Common misunderstandings and problems

To avoid any misunderstandings, we would like to briefly explain the exact meaning of the information on the water resistance of a wristwatch. Manufacturer information in meters can be particularly misleading for laypeople. A wristwatch that the manufacturer says is water resistant to 20 bar can, in theory, be worn in water up to a depth of 20 meters. But it all depends on the circumstances in practice!

Both ATM and bar refer to the water column and the prevailing pressure under water, with the test pressure being built up under laboratory conditions. The actual water pressure that a watch can withstand can, under certain circumstances, differ from the value given in meters. For example, if the watch is left in the sun and you then jump into cold water, you can assume that the water resistance will be reduced in terms of the meter value. The same applies to diving in rough waters and numerous other scenarios that occur again and again in practice.

Popular models and manufacturers

Finally, we would like to name a few brand watches that fit the description "waterproof up to 10 ATM" and are definitely worth a closer look:

• TAG Heuer Monaco x Gulf : Automatic watch with square case

• TAG Heuer Carrera Calibre 16 : Chronograph with date and day of the week display

• TAG Heuer Link: Elegant quartz watch with marbled dial

• Zenith Chronomaster Sport : Chronograph with small second, date and luminous indices

• Rolex Cosmograph Daytona : Chronometer with screw-down crown

• Rolex Milgauss : Magnetic field-resistant wristwatch with characteristic lightning hand

• Rolex Datejust 41 : Automatic watch with date and Roman numerals

• Rolex Sky-Dweller : Chronometer with luminous hands, date scale on the dial and small second

• Rolex Oyster Perpetual : Sporty steel watch with luminous indices and hands

• Omega Speedmaster 38 Co-Axial : Automatic chronograph with date display

Conclusion: The right watch for your needs

A watch that is worn every day should not be affected by moisture and splashes of water. Models with a water resistance of 5 ATM or more can even be left on the wrist while showering, and watches with a water resistance of up to 10 ATM can even survive a visit to the swimming pool unscathed. How waterproof a watch needs to be in a specific case to fully meet the wearer's expectations depends largely on the activities it is worn for. It is always important to remember that the water resistance of a watch can decrease over time. It is therefore essential to take good care of your favorite waterproof watch and have it inspected regularly by a specialist so that contact with water does not cause damage to the movement in the long term.