Waterproof Watch Guide: Water Resistance Explained

This article covers water resistance rating on sports watches. If you are searching for waterproof watches for swimming, we expect to have articles on finding a water resistant watch swimming soon.

When it comes to buying a watch, a feature that is displayed prominently on most watches is the water resistance of the timepiece, but what does this really mean? What is the difference between a water resistant and waterproof watches? These terms are somewhat vague, so here we will provide a complete explanation of how sports watches are rated for water resistance.

The way watches are rated for water resistance is by placing a watch in a pressure chamber that is comparable to a given depth under standard water pressure. While most watches are marked “water resistance”, if no depth rating is specified (50 meters, 100 meters, etc), then these watches are NOT designed to be submerged below the surface of the water at all. They may hold up under certain conditions for a while when submerged, but if kept underwater for an extended length of time they will eventually leak, so to label a watch waterproof, you will need to check the product specification very carefully to ensure your watch is tested in underwater conditions.

Generally if you need a watch that you can use below the surface of the water, ensure that you get a waterproof sports watch that features a screw-down crown and screw-down caseback. Watches with these are extremely effective at resisting water seepage, whereas a normal standard sports watch will lead to dissapointing results if you use it for too long in water. When buying a watch you should keep in mind that “water resistant” generally means resistant from accidental wetting. Say if you drop it into the bath by accident, but only for a couple of seconds.

Water resistancy is tested under static conditions and under the pressure that is equivalent to a certain depth below the surface. Given that pressure can sometimes be equated to the velocity that a watch moves under water, if you are thrashing your arms around in the water, say if you’re swimming for instance, the resulting pressure that the watch is under is greater than the actual depth of the water itself. If the resulting pressure is greater than the rated water reistancy, then the watch could be at risk of leaking.

Sudden changes in temeprature can also be a factor, like when you wear your watch in a hot bath. The sudden change in temperature that is experienced when you sit down in the bath, serves to put strain on the rubber gaskets, steel case and base metal which risks your watches water resistancy and integrity of it’s sealing capacity. Unless you have a waterproof sports watch, or a watch with a high grade of water resistance, then you should ensure that you take your watch off when bathing.

You should also keep in mind that even with waterproof sport watches, the precision gaskets that protect the setting stem, case-back or the crystal dial window at the front of the watch will get weaker over time due to normal wear and tear. Your watch should be inspected periodically and when it reaches the point where it is worn, should be replaced or kept away from water. Corrosion of the case-back sealing area or the crown in waterproof sports watches, is another area of concern and these areas should also ideally be inspected.

How Submergible Is Your Watch?

The general way of telling whether a watches waterproof rating is to check the label on the dial (usually between the 4 and 7 o’clock marks) or on the case-back to review the rating of a particular time-piece. A watch with no depth rating can be considered not designed for deliberate submergion beneath the water. According to guidelines issued by the Federal Trade commission since the 1960′s, watchmakers are not permitted to print the worlds “waterproof” on their watches. This has aided us to achieve a more honest means of accurately appraising a watch. Even timepieces that are designed for deap-sea diving can not claim to be waterproof as the seals that keep water out are not entirely immune from the effects of deterioration, chemicals and aging. This is a globally recognized standard.

The following table can be used as a general guide to the suitabiliy to different actvities of a given watch rating. Generally the following “rules” apply to the majority of sports watch water resistance ratings.

Non-Water Resistant Watches: These should not be exposed to the water AT ALL. You must take extreme care that these are not exposed to sitautions that could result in the entrance of moisture such as steam for instance.

Water Resistant: Water resistant watches are not intended for swimming or bathing, they should not be explosed to a direct flow of water under pressure such as water from a shower, a faucet or garden hose, although they are safe from accidental wetting.

100m Resistant: These are designed to be used in activities involving exposure to water. They are not, however designed for scuba diving, where considerable pressure is involved.

Category Water Resistance Professional Deep Water Diving Recreational Scuba Diving Bathing, Swimming or Snorkeling Accidental Wetting
Divers’ Watches 300 Meters+
990 Feet
30 ATM

(incl. saturation)
200 Meters
660 Feet
20 ATM

(not saturation)
High Grade Water Resistant Watches 150 Meters
500 Feet
15 ATM
100 Meters
330 Feet
10 ATM
General Water Resistant Watches 50 Meters
165 Feet
30 Meters
100 Feet
10 Meters
33 Feet
Not Water Resistant

When using analog waterproof watches for swimmers, you should alway ensure that the crown and case-back are screwed in and that you reframe from pressing any of the push-buttons while under water. After use in the water, the watch should be wiped dry before you attempt to change any settings.

In the world of watches, a manufacturer needs to obtain an IP code rating for a particular watch in order for the mark of water resistance to appear anywhere on the watch body. It should be noted that ratings apply to individual parts of the watch and not the timepiece as a whole so if a “WR” rating is printed on the wrist band and not the case, then the rating applies to the band, and not necessarily the case as well. IP stands for International Protection or Ingress Protection and there are various different IP codes for different types of protection, but with regards to water protection there are two certifications, ISO 2281 and ISO 6425.

Water Resistance Requirements In ISO 2281 Watches

The ISO standard for both an analog and digital waterproof watch is a standard which prohibits the term waterproof being used on watches. In order to pass this certification, it is not required that every individual watch be subjected to testing, lot testing is also required. This standard was only intended for watches that are intended for ordinary daily using during exercise under water for brief periods and under conditions where temperature and water pressure may vary. The tests include:

Immersion for one hour in 10cm of water

Immersion and with a force of 5 Newtons perpendicular to the crown and pusher buttons in 10cm of water for 10 minutes

Immersion in 10cm of water at a range of temperatures (40°C, 20°C, 40°C) for 5 minutes each and with transition between temperatures less than 5 minutes. There should be no evidence of water intrusion or condensation.

Immersion in a pressure vessel and subjection to a rated pressure for 1 hour. There should be no evidence of water intrusion or condensation.

Exposure to overpressure of 2 bar. No more than 50µg/min of air should penetrate the case.

The ISO 6425 Divers’ Watch Standard

ISO also have a certificate called ISO 6425, which is generally intended as an entry-level standard for waterproof watches intended for divers. The key difference between this and ISO 2281 is that that each and every watch must be tested and to 125% of the rated depth, so for example a 300M watch would be tested to 375M. The tests in ISO 6425 are more comprehensive and include the following:

Immersion in 30 cmof water for 50 hours.

Immersion in 30cm of water under 125% of the rated pressure under a force of 5 N perpendicular to the crown and pusher buttons (if any) for a period of 10 minutes.

Immersion in 30 cm of water at the following temperatures for 5 minutes each, 40°C, 5°C and 40°C again, with the transition between temperatures within 1 minute. There should be no evidence of water intrusion or condensation.

Immersion of the watch in a suitable pressure vessel and subjecting it to 125% of the rated pressure for 2 hours. The pressure must be applied within 1 minute. Subsequently the overpressure shall be reduced to 0.3 bar(negative pressure) within 1 minute and maintained at this pressure for 1 hour. No evidence of water intrusion or condensation is allowed.

For mixed gas diving the watch has to be immersed in a suitable pressure vessel and subjecting it to 125% of the rated pressure over a 15 day period in a helium-enriched breathing gas mix.

When completed, the overpressure is to be reduced to normal pressure within 3 minutes with no evidence of condensation, water intrusionor or any other problems caused by internal overpressure.

(Optional) Exposure of the watch to an overpressure of 2 bar with no more than 50µg/min of air permitted to enter the case.

With the exception of thermal shock, all subsequent ISO 6425 testing is conducted at 18°C to 25°C temperature.

Whatches that have been confirmed to conform to ISO 6425 are marked with the word DIVER’S to denote that they are designed for diving. Watches that are ISO 6425 compliant can be considered waterproof despite the fact that manufacturers are not permitted to print the world “waterproof” on the case of the watch. There are many mens waterproof watches as well as ladies waterproof watches that are ISO 6425 tested. There are even kids waterproof watches and cheaper version such as Timex waterproof watches. These watches are generally more expensive, but are also much tougher due to the rigour of the testing process. Classic diving watches come in analog format, however there are many waterproof digital watch designs from watchmakers like Suunto that provide you with advanced, modern diving features and perform considerable “number crunching” that would otherwise need to be manually determined using diving tables.

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