While “water resistance” is a fairly common feature of most watches, there is a lot more to it than just printing a number on a dial. Whether you’re a diving enthusiast, headed for a beach vacation, or just curious about water resistance, in this article we will provide you an overview of the topic of water resistance and how it applies to watches.
So, What Does The Rating Mean?
The water resistance rating assigned to a watch indicates how well the watch is sealed against the possibility of water entering it. Watches are independently static pressure tested by brands and given an ATM (atmosphere) or BAR rating depending on the amount of pressure the watch can withstand. This rating is then converted into an equivalent depth measurement, which is often indicated on the watch's dial or caseback. For example, a 30ATM or 30BAR can withstand pressures equivalent to 300 meters.
Once these ratings are determined, they are used to indicate how well the watch will perform when subjected to water pressure and acts as a type of a guide to help indicate what types of activities it can be utilized for -- whether it be swimming, scuba diving or washing your dishes.
How Are They Tested?
There are 2 commonly used water-resistance testing methods:
During this test, the watch is placed in a chamber and the air-pressure is increased. As the pressure increases to the appropriate atmospheric pressure, the testing machine scans the chamber to detect whether there is even the slightest variation in the watch's case size. If a variation is detected, the watch is considered compromised and not water resistant.
During this test, the watch is placed in a chamber which is half-filled with water and half air. Air pressure is increased to the appropriate atmospheric pressure while the watch is out of the water, then the watch is slowly immersed into the water. Once the watch is completely immersed, the air pressure is slowly released. If bubbles come out of the watch, it means that air seeped into the watch prior to immersion. This means the watch is compromised and not water resistant.
What About Dive Watches?
For those of you who are more adventurous and like to dive, there are strict standards for the category of dive watches. The standard is called the ISO 6425 watch standard and it incorporates a set of rules for the watch industry for watches marketed as "dive watches", with more extreme water resistance ratings of 300 meters and beyond. The ISO 6425 testing includes condensation testing, temperature shock testing and overpressure testing at 125% of the watch's rated pressure. In addition, sampling is not allowed, all watches need to be tested or they are not allowed to be sold as a dive watch.
In this article, we have provided you with a general understanding of water resistance ratings for watches. Are they important? Well...it depends! If you are planning on diving and need a watch that holds up to the pressures of the deep, you should certainly get a quality dive watch, with a 300m or 500m rating as a backup to your dive computer. If you are a desk diver...it is more of a conversation piece than a tool, and a 30 meter rated watch would work just fine. Either way, you are now armed with a little bit more knowledge on the topic for the next time you are shopping for a watch or just talking about watches with fellow hobbyist.
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