All About Water Resistance in Watches

Testing procedures, certifications, and helium escape valves

Welcome to Part Two of All About Water Resistance In Watches. In Part One, I talked about design factors that contribute to water resistance, some basics about pressure, common depth ratings and what they practically mean, and a little about the aging process and how it affects a watch’s ability to seal water out.

In this post, I will go into detail about how watches are tested for water resistance, the certifications and standards that relate to water resistance and diver’s watches, and an explanation of Helium Escape Valves (HEVs). There’s a lot of test information to get through, but for my flavor of watch nerd, it is all very interesting and I hope you enjoy.

Testing Procedures and Certifications

As I said in Part One, water resistance ratings aren’t verified by divers hauling watches into the depths of the ocean and seeing which ones leak, so how is it actually done?

There are two primary ways to test watches for water resistance and they each have pros and cons; dry testing involves pressurizing a watch in air, and wet testing is done in pressurized water.

Dry Testing

Dry testing is probably the most common in practice; many watchmakers will run a quick dry test after they close up a watch for the last time before returning it to the customer. This ensures that everything is properly seated against the gaskets and if the watch does fail the test, it doesn’t risk getting the movement wet.

How does a dry testing machine actually work? The watch is set in a pressure chamber with a sensor touching the front or back of the case. The sensor can detect minute changes in the size of the watch case; when the watch is pressurized in the chamber, it gets compressed slightly. If a leak occurs and air rushes into the case, the watch will expand and the sensor will send an electrical signal to the tester’s computer, letting the computer know that there was a leak. Also, if there is a bad leak, the watch may not compress at all when the chamber is pressured, which would also be a failure. While dry testing is quick and low risk, it does have some limitations.

Most dry testing machines don’t have a high pressure capacity; max pressures are often below 10 bar. While these machines can test many non-dive watches to their marked resistance pressure, they aren’t sufficient for most watches meant for water activities. Dry testing machines also won’t help you diagnose what parts of the watch are leaking if there are leaks. Lastly, because the sensor must be able to detect such small changes in case size, these types of testers are prone to false failures; that is, the watch wouldn’t let any water in, but the dry tester senses a failure anyway.

Wet Testing

Wet testing is a more direct and accurate method than dry testing for determining water resistance; it is primarily used for watch certification (see the ISO Standards section below), testing watches with high pressure or depth ratings, and leak detection and location. To prevent water from damaging a watch’s inner workings if there is a leak during the test, wet tests are usually done on an empty watch case. There are two main types of wet testers that have different primary uses.

A vacuum-type wet tester is used to locate leaks in a watch. This machine has a transparent pressure vessel that is partially filled with water. The watch is kept out of the water during pressurization and then submerged before the vessel is depressurized. A visible stream of bubbles will escape the case at the spot of any leak, allowing the user to locate the point of failure and fix it. Vacuum testers usually have pressure capacities of 10 bar or less, similar to dry testers.

The high-pressure water chamber is for serious water resistance testing; these machines are often capable of producing pressures in excess of 120 bar, far more than most professional dive watches are rated for. High-pressure testers are used for certifying water-resistant watches and can maintain pressure for hours at a time. Many of these testers don’t have windows to view the watch through, so you won’t know if the watch leaked until you perform a post-immersion test (such as a condensation test like the one described in ISO Standard 22810 below).

Wet testing is the best way to be sure that your watch is water resistant, and some vacuum testers are affordable enough for serious watch enthusiasts to buy for home use. But enough about testing machines, let’s talk about water resistance standards and certification.

The ISO Standards

There are two international standards (developed by the International Organization for Standardization – ISO) that regulate watches marked “water-resistant” and “diver’s,” which are ISO Standards 22810 and 6425 (respectively). These standards specify testing procedures that watches must be capable of passing and features the watches must include in order to use these markings.

The standards are not freely available, but you can purchase them online. I’m a thorough researcher, so I paid for them and have summarized them below. Please note that ISO standards are updated occasionally, and at the time of this writing, the latest versions were ISO 22810:2010 and ISO 6425:2018. The 22810 standard superseded ISO 2281:1990, and the previous version of 6425 was released in 1996.

ISO 22810 – Water-resistant Watches

ISO 22810 defines testing procedures that a watch should be able to pass in order to be labeled “water-resistant” to a certain depth. Importantly, the standard does not stipulate actual testing procedures that should be used by manufacturers during the development or production of their watches; the tests described would be used “in the event of a dispute” to verify that a watch actually meets the standards of its label.

The standard also states that the manufacturer is responsible for defining the watch’s warranty conditions, precautions the customer should take to maintain the watch’s quality over a long period of time, and the activities that the watch is meant for. Additionally, an acknowledgment is made that the quality and permanence of water protection are affected by not only the watch’s manufacturing and design but also the particular piece’s history (services, physical shocks, etc.). So treat your watch gently and have it serviced at the manufacturer-recommended intervals if you want the water protection claim to remain valid.

ISO 22810 Testing Procedures
The standard defines four immersion tests that a watch must be able to pass to be considered water-resistant. A condensation test (discussed later) is used to verify that the watch case has not been breached; if the watch fails the condensation test after any or all of the four immersion tests, it fails to meet the standard.

For all tests, ambient temperature (and water temperature, unless specified otherwise) are kept between 18°C and 25°C (or 64.4°F and 77°F). The watch’s components should be actuated (if possible) and reset before starting the testing process.

Alright, time for the fun part… let’s talk Test Procedures!

ISO 22810 Immersion Test One – Resistance to Overpressure
This is the main test for the watch which determines the pressure or depth that can be marked on it. Overpressure just means pressure greater than ambient pressure.
Procedure
For the test, immerse the watch completely in a pressure container filled with water. Raise the pressure (within 1 minute) to a minimum overpressure of 2 bar (more on the choice of overpressure later). The watch is held at this pressure for 10 minutes before being brought back down to ambient pressure over the course of 1 minute or less.

ISO 22810 Immersion Test Two – Water Resistance at Shallow Depth
Immerse the watch in water to a depth of 10 cm and keep it there for 1 hour.

ISO 22810 Immersion Test Three – Water Resistance When Strain is Placed on the Operative Components
The watch is immersed in water to a depth of 10 cm for 5 minutes. During the immersion, a force of 5 Newtons (1.124 lbs) is applied to the crown and each of the other “operative components” in a perpendicular direction (90°) to their axes of operation.

ISO 22810 Immersion Test Four – Water Resistance on Exposure to Thermal Shocks
Immerse the watch to a depth of 10 cm, successively, in water at 40°C (104°F) for 5 minutes; in water at 20°C (68°F) for 5 minutes; and finally in water at 40°C (104°F) again, for 5 minutes. The watch must be transferred from one immersion to the next in less than 1 minute.

ISO 22810 Condensation Test

This condensation test is used to verify that no water has entered the watch during testing. Both ISO 22810 and 6425 use the same test, as described below.

Place the watch on a heating plate set between 40°C and 45°C (104°F and 113°F) and leave it there “until the watch glass reaches the temperature of the plate”
Place a drop of water (or a wet cloth or pad) on the glass. The water should be at ambient temperature, as defined above
After “around 1 min,” wipe the glass with a cloth to dry it

Results and Notes
If condensation can be seen on the internal surface of the glass and remains there for more than one minute, then the watch fails the standard.

The watch can be thoroughly dried and re-tested, in case the condensation was a result of the watch case being closed in a very humid environment.

For step 2, the choice between a drop of water, a wet cloth, or a wet pad, depends on the glass’ thickness. Glass thicker than 2 millimeters may not respond reliably to a drop of water, so it’s recommended that a wet cloth or pad is placed on the watch instead.

Marking Watches That Meet the ISO 22810 Standard
If a watch can pass the condensation test after undergoing the four immersion tests, it can be marked “water-resistant” (or its equivalent in a few other languages). In the Resistance to Overpressure Test (immersion test one), the watch is tested at a minimum overpressure of 2 bar. If the watch can pass this test at a higher overpressure, that pressure can be marked on the watch after “water-resistant”, i.e. “water-resistant x bar” where x is the overpressure applied during the test (only whole numbers are allowed). This value can also be marked as depth in meters corresponding to the overpressure applied; remember from Part One that 1 bar corresponds to a depth of 10 meters.

ISO 6425 – Divers’ Watches

ISO 6425 defines testing procedures that a watch must pass, and features a watch must have, in order to be labeled “diver’s” i.e. suitable for diving. Unlike ISO 22810, this standard does stipulate the actual testing procedures that must be used by manufacturers. A few other ISO standards are referenced in ISO 6425 as additional requirements, but I won’t go into detail on these since this discussion is focused on water resistance.

Like ISO 22810, this standard requires the manufacturer to define the watch’s warranty conditions, precautions the customer should take to maintain the watch’s quality over time, and the activities that the watch is meant for.

Diver’s Watch Features
In addition to their water resistance, diver’s watches must include features that improve the visibility of necessary information, helping the user dive more safely.

Diving Time Indicator
Diver’s watches must include some type of diving time indicator such as a rotating bezel, digital display, etc. This indicator should be protected from accidental adjustment and must allow for an indication of the diving time with a minimum resolution of 1 minute over at least an hour. For analog displays, there should be clear markings spaced, at most, every 5 minutes.

Visibility
The dive time indicator and other important markings on the watch must be legible at low light, and in darkness after being exposed to light as stipulated in ISO 17514, clause 4. The readability of the following items is then checked at least 3 hours after the light exposure, at a distance of 25 centimeters (9.84 inches) in complete darkness:

Time display (the minute and hour indicators must be clearly distinguishable from each other)
Dive time indicator, which must have an uncertainty of ±2.5 minutes or less
The minute markers
An indication that the watch is running (usually a moving second hand)
A battery end-of-life indication, if applicable

ISO 6425 Water-Resistance Testing

The 6425 standard defines 4 tests for water resistance. These tests are similar to the ones defined in ISO 22810, but they are much more stressful to the watch. The same condensation test described in ISO 22810 is used in ISO 6425 to verify that the watch case has not been breached by water. This standard requires the condensation test to be carried out before starting the water resistance tests and after each of the four tests; if the watch fails the condensation test after any of the immersion tests, it fails to meet the standard.

For all the tests, ambient temperature (and water temperature, unless specified otherwise) are kept between 18°C and 28°C (or 64.4°F and 82°F), which is slightly different than the range defined in 22810.

ISO 6425 Immersion Test One – Functional devices in shallow water
For this test, all functional mechanical devices are operated, unless the documents accompanying the watch (i.e. user’s manual, etc) prohibit their use when the watch is submerged.

Immerse the watch in water to a depth of 30 centimeters (11.8 inches), and while underwater, operate all the relevant mechanisms; the watch must function correctly
Keep the watch immersed for one full day
After the full day of immersion, and while still underwater, operate all the relevant mechanisms again; the watch must still function correctly
Keep the watch immersed for another full day
Remove the watch from the water and wipe it dry
Carry out the condensation test
The watch must function normally after the test

ISO 6425 Immersion Test Two – Resistance when strain is applied to crown and other setting devices
This test is similar to ISO 22810’s Immersion Test Three.

All components that can be secured for water resistance must be locked (i.e. screw-down crown and pushers, etc.)
Apply a force of 5 Newtons (1.124 lbs) to the crown and other operative components in a perpendicular direction (90°) to their axes of operation
Immerse the watch in water at an overpressure corresponding to 125% of the depth that will be marked on the watch (10o meter minimum marked depth); keep the watch immersed like this for 10 min
Remove the watch from the water and wipe it dry
Perform the condensation test
The watch must function normally after the test

ISO 6425 Immersion Test Three – Functional devices at a water overpressure
Unlike Immersion Test One, mechanical devices that the manufacturer prohibits from use when the watch is submerged must be operated if they are not protected from accidental operation.

All components that can be secured against water ingress must be locked (i.e. screw-down crown and pushers, etc.)
Immerse the watch in water and, over at most 10 minutes, apply an overpressure equal to the depth that will be marked on the watch (100-meter minimum)
Operate all devices specified to be used underwater, as well as devices not protected against inadvertent operation, 5 times each
Maintain the overpressure for 30 minutes
Reduce the overpressure to 0.3 bar, within 10 minutes, and maintain this pressure for another 30 minutes
Remove the watch from the water and wipe it dry
Perform the condensation test
The watch must function normally after the test

ISO 6425 Immersion Test Four – Resistance at a water overpressure
This is the main test for the watch that determines the depth that can be marked on it.

Immerse the watch in water and, over at most 10 minutes, apply an overpressure corresponding to 125% of the depth that will be marked on the watch (100-meter minimum marked depth)
Keep the watch at this pressure for 2 hours
Reduce the overpressure to 0.3 bar, within 10 min, and maintain this pressure for one hour
Remove the watch from the water and wipe it dry
Carry out the condensation test
The watch must function normally during and after the test

ISO 6425 Additional Testing

Along with the water-resistance testing just described, ISO 6425 compliance requires passing some additional tests and standards. They are: magnetic resistance test from ISO 764; salt-spray test from parts of ISO 9227, with the bracelet on the watch; shock-resistance tests described in parts of ISO 1413, performed on the watch without its bracelet; resistance of attachments test, not from another standard but described in 6425; temperature cycling test, also described in 6425.

Additional Testing for Saturation Diving Watches

Some diver’s watches are specially designed for Saturation Diving (more on this in the section on Helium Escape Valves, or HEVs, below). ISO 6425 recommends an additional test for watches in this category and allows an additional marking to differentiate watches that have passed this test.

The test will make more sense after reading the HEV section, but it entails keeping the watch at an elevated pressure in helium gas for 15 days, then quickly bringing the overpressure back down to zero (ambient pressure). This depressurization must occur within 10 minutes. The particular overpressure is dependent on the watch’s depth rating but can be up to 40 bar at most. The watch must pass all the tests discussed above before undergoing the helium overpressure test, and then it must pass Immersion Test Four again afterward.

Watch Sampling and 100% Testing

During the certification process, ISO 6425 requires sample watches of a certain model to pass all the tests defined in the standard, in a certain order (this is called type testing). Once the watch has been certified and begins the production phase, each individual watch only has to pass Immersion Test Four (100% testing).

Marking Watches That Meet ISO 6425

If a watch passes the type testing phase and becomes a certified diver’s watch, it can be marked “diver’s watch x m” (where x is the depth in meters, m, corresponding to the overpressure used during testing), or the statement’s equivalent in a few other languages.

If the watch passed the helium overpressure for saturation diving test as well as the other tests I talked about, it can be marked “diver’s watch x m for saturation diving”, or its equivalent in a few other languages.

Watches That Aren’t Tested to ISO Standards

So if a watch isn’t marked “diver’s” can you still dive with it? Potentially, yes. If a watch isn’t marked water resistant, can you still get it wet? Probably not.

One important point I need to make about the ISO standards is that they are voluntary; as a watchmaker or watch manufacturer, you don’t need to test your watches to the ISO standards if you don’t want to use the ISO markings. There are many brands that do not test to ISO standards, but still make very capable watches; in fact, some of the best dive watches in production are not ISO 6425 certified. This is more common for dive watches than generally water-resistant watches, though; few watches not marked water-resistant actually are.

Why is this? For the case of ISO 22810, it’s probably because the standards are very lax and leave testing procedures up to the manufacturer; the amount of time and money needed to satisfy this standard is very low. For dive watches, it tends to be somewhat the opposite. Manufacturers often produce very high-quality watches for diving that would easily pass the tests prescribed in ISO 6425; the cost of going through the certification process would be an unnecessary expense.

Does PADI Have a Standard for Dive Watches?

PADI is the Professional Association of Diving Instructors, the best-known global scuba training organization. Some Seiko dive watches are marked with the PADI logo, leading some to ask if there is a PADI standard for dive watches. There is not.
Seiko is an “official watch partner” of PADI and was given permission to use the PADI logo on some of their dive watch models. The PADI marking does not signify additional capabilities or certification, though the PADI-marked watches are all ISO 6425-certified diver’s watches (as are other watches from Seiko).

Helium Escape Valves (HEVs)

While shopping for or researching dive watches, you may have heard the term Helium Escape Valve or HEV (also known as helium release valves, or gas escape valves – see the image of the Rolex Sea-Dweller Deepsea at the top of this post). What are HEVs and why aren’t they included in the list of Resistance Factors I presented in Part One? The reason I didn’t discuss HEVs in the previous part of this series is that they don’t actually make a watch more water-resistant, and 99.9999% of people (maybe not exactly) will never need one on their watch. I describe what they are below.

Saturation Diving
Most people are familiar with free diving and scuba diving. In free diving, the diver holds their breath while underwater and uses no breathing apparatus. Scuba diving allows the diver to breathe while underwater by using a breathing apparatus carried by the diver which provides air at ambient pressure (SCUBA stands for Self-Contained Underwater Breathing Apparatus). A third type of diving, which is less well known, is saturation diving. In saturation diving, divers are held at dive pressures for extended periods to reduce the wasted time and resources required for them to return to normal pressure between dives. Saturation diving is used in special commercial settings and has been used in scientific settings as well (such as for the Tektite I and II programs – see image above).

Helium in the Mix
Saturation divers usually breathe a helium and oxygen mixture to reduce the physiological effects of long-term exposure to high-pressure nitrogen, which is a major component of the air we normally breathe. Helium atoms are very small compared to water, nitrogen, or oxygen molecules, and easily get past the typical gaskets meant for keeping water out of a watch. This buildup of helium gas is fine at saturation pressures; once the diver and watch are finally brought back to surface pressure during the decompression process, the excess pressure in the watch can cause the crystal to be blown off.

Helium out of the Mix
This is where HEVs come in. HEVs are small one-way valves that allow excess pressure inside the watch case to be released when the external pressure is lower. These valves do not allow pressure to flow in the opposite direction (higher pressure from outside the case to flow inside), hence the “one-way” part of the name. HEVs typically look like very small, flush, unmarked buttons on the side of the watch case, similar to reset buttons found on wifi routers and other electronics that you press using a pen or paper clip… just don’t start poking your HEV if your watch has one.

Do All Watches Used for Saturation Diving Need HEVs?
No, there are other ways to get around the helium issue during a saturation dive.
HEVs were first seen on the Rolex Sea-Dweller in the late 1960s; the first commercially available watch with an HEV was the Doxa Conquistador, released shortly thereafter. Other brands on the dive watch scene (namely Seiko and Omega) chose to solve the issue by creating higher-quality seals that were impenetrable to helium in the first place, so no gas would seep into the case over the duration of the saturation dive.
The other way to prevent your watch from over-pressurizing is simply by opening the crown before the decompression process begins, so gasses can move in and out of the watch case freely. This is not a perfect solution though, as dust and dirt can enter the watch when the crown is opened, leading to more frequent maintenance.

Let’s Wrap This Up

There’s a lot to know about water-resistant watches, testing, and dive watches; I’ve just given a thorough primer in this two-part series. I hope you found the content useful and interesting. If you’d like more information on anything I covered in Parts One or Two, please leave a comment below. Until next time.
– Niccoli Scalice, CoMo