Water Resistant mark

Water Resistant is a common mark stamped on the back of wrist watches to indicate how well a watch is sealed against ingress of water. It is usually accompanied by an indication of the static test pressure that a sample of newly manufactured watches was exposed to in a leakage test. The test pressure can be indicated either directly in bars, or (more commonly) as an equivalent water depth in meters (in the United States sometimes also in feet).

An indication of the test pressure in terms of water depth does not mean that the watch was designed for use in such water depths. For example, a watch marked at 30 meters depth cannot be expected to withstand activity in a swimming pool, let alone cotinue to function at 30 meters under water. This is because the test is conducted only once using static pressure on newly manufactured watches. In practical use, a watch is subjected to variations in pressure which greatly add to the static pressure of the water. Examples of this include the movement of a swimmer's arm through the water, or violent sprays encountered in water skiing. A test suitable for qualifying a diving watch for repeated usage in a given depth would have to include safety margins and an accelerated aging test of the seals. It would futhermore need to take into account the effects of rapidly changing water pressure and temperature, as well as dynamic mechanical stresses encountered by a watch.

The "Water Resistant" mark has come to replace the "Water Proof" mark and is defined by international standard ISO 2281 "Horology - Water-resistant watches". This standard was only designed for watches used in everyday life that must be water resistant during exercises such as swimming. None of the tests defined by ISO 2281 for the Water Resistant mark are suitable to qualify a watch for scuba diving. (A completely separate test standard for divers watches is ISO 6425, which defines test standards for watches suitable for scuba diving in depths of 100 m or more. Watches conforming to ISO 6425 are marked with the word "Divers".)

Typical ISO 2281 static test pressures used for watches are 30, 50, 100, 150, 200, and 1000 meters.

The following rules of thumb are given by some manufacturers how the static test pressure and the practical survivability of watches relate to each other:

test pressure	equivalent water depth	device should be suitable for
5 bar	50 m	immersion without pressure such as being worn while washing up dishes.
10 bar	100 m	surface swimming
20 bar	200 m	scuba diving to a depth of 30 m
100 bar	1000 m	pressure greater than 500 m, which is at the limit of human endurance

In practice, the survivability of the watch will depend not only on the water depth, but also on the age of the sealing material, past damage, temperature, and additional mechanical stresses.

The ISO 2281 standard specifies a detailed testing procedure for each mark that defines not only pressures but also test duration, water temperature, and other parameters. For example, to receive the "Water Resistant 30M" mark, the watch is first immersed 10 cm under water for 60 minutes, followed by 10 minutes under a pressure of 3 atm (approximately 73 PSI), after which no water must have leaked into the case.

See also

• IP Code

External links

• Water Resistance Explained on Breitling Site