Understanding What 'Water Resistance' Really Means

*Originally published August 2014

We get a lot of questions about water resistance, especially in summer. Among the questions asked of us: “Can I swim or shower with my watch? What makes it water resistant and can it become non-water resistant? Do I have to do anything special to keep it water resistant?” So on and so forth. Interestingly enough, these are all good questions. So, today, we try to answer some of them.
To begin with, no watch is waterproof. Watches can be rated water resistant to a certain depth that is typically pre-determined via extensive tests in laboratory conditions. Factors that make a watch water resistant include special gaskets, screw-in case backs, screw-down crowns, and more.

Gaskets: In everyday life, gaskets or O-rings can age, and that aging can affect the water resistance of a watch. Sometimes these gaskets — usually made of rubber or silicon, depending on the watch — can erode over time and begin to break down. They should be checked annually. Additionally, when you have your watch serviced, or the battery changed, the work should be done by an authorized servicer of that brand. Otherwise, the re-sealing of the case or the replacement of the gaskets could be improper – rending the watch non-water-resistant. We suggest you use only authorized retail service centers to have your watch serviced.
Crowns: The crown (which many refer to as the watch stem) is the single most important factor in water resistance. Because the stem of the crown moves through a hole in the case side and reaches into the movement, water leakage could do serious damage to the watch caliber. To ensure water resistance, most top watch brands create “screw-down” crowns. These are crowns that are threaded and screw closed tightly to compress the seals and prevent water from going in. The crown should never be unscrewed or operated while in the water. We do not recommend swimming with a watch that does not have a screw-down crown.
Casebacks: There are a variety of different types of casebacks on timepieces that range from snap-on to screw-in varieties. Snap-on case backs typically offer water resistance to just about 30 meters, and any deformity in the gasket can affect the resistance of the watch to water. Casebacks that are put into place with individual screws offer a better seal and generally can go to depths of 100 meters. However, screw-in casebacks – where the caseback and case are threaded and screwed together – offer the best assurance. Generally, watches water resistant to more than 100 meters (330 feet) will have screw-in casebacks.

In addition to the above information, it is important to know that showering with a water resistant watch is not necessarily a good idea. The reason is that showers are generally done in hot water and the temperature of the water can affect the gasket shape and seal. Additionally, if one is moving from pool to hot tub and back again, the sudden changes in temperature could have an affect. For this reason, as well, we recommend having your watch tested for water resistance once a year.
So, the quick guide: If a watch doesn’t say water resistant, or is water resistant to 30 meters, we recommend you don’t wear it in the water. Watches that are water resistant from 30-50 meters can come into contact with water via rain or hand washing. Watches resistant from 50-100 meters can be used in pools, but jumping or diving off of a diving board with a watch on is sometimes not a good idea, as the rapid change in pressure can be jarring for the timepiece. For serious swimming, snorkeling and showering it is best to have a watch that can go to depths of 100-200 meters, or more. Stay tuned. Later this week, we will bring you the low-down on dive watches.