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Watch Water Resistance – The Truth Behind Depth Ratings

You’ve just bought a new watch that is marked as “water resistant to 30 meters” to wear on your upcoming beach vacation. After a few hours of swimming, you look down at your watch to check the time only to see unmoving hands behind the glass of what is now a tiny, wrist-bound aquarium.

Your watch is completely ruined, even though you never got close to 30 meters deep. What gives?

The Truth About Your Watch’s Depth Rating
The reason most watches can’t survive a trip to their rated depths has to do with how watch water resistance is tested.

During testing, watches are placed in small chambers that are pressurized by compressors to different ATM levels, a measurement based on earth’s atmospheric pressure. If the chamber is pressurized to 3 ATM and doesn’t fail, it can be rated at the equivalent depth measurement of 30 meters (1 ATM is equal to 10 meters).

However, watches are tested under static air or water pressure for only a short time—usually 10 minutes. These conditions are very different from what your watch will experience during real use, so its depth rating is not exactly reliable outside the laboratory.

Why Different Watches Have Different Ratings
Most brands do watch water resistance testing that complies with ISO 22810 water-resistant watches standard or ISO 6425 divers’ watches standard. Watches that comply with ISO 2281 are usually designed for ordinary use only. Dive watches must be much tougher to stand up to the high pressure levels at diving depth, so ISO 6425 has much stricter testing requirements.

What separates watches that are rated at different depths are their materials, design, and construction. A titanium or stainless steel case can withstand greater pressure than one made of gold. Gaskets made of nylon, teflon, or rubber will degrade at different rates. Case backs with a screw-in design maintain a seal better. All of these factors contribute to better watch water resistance.

Some Guidelines to Prevent Water Damage
Before your next trip to the water, use the simple guidelines below to decide if you should leave your watch at home:

No Rating Stay away from all water sources–even rain, splashes, or steam. Absolutely no swimming or diving.
Water Resistant 30M Splash and rain resistant. Suitable for everyday wear. No swimming or diving. Water Resistant 50M Okay for light swimming, rafting, and fishing. No diving or snorkeling. Water Resistant 100M Suitable for swimming, surfing, snorkeling, and water sports. No diving. Water Resistant 200M Great for all water activities aside from diving. Diver’s 200M (or more) Protected from pressure levels experienced during normal recreational diving in depths of 30 to 40 meters.
It’s important to remember that these ratings only apply when your watch is in good, working order. If the gasket in your crown seal gets pinched or dries out, your watch could fail regardless of its rating.

Better Watch Water Resistance Through Proper Maintenance
Fortunately, you can prevent this with proper maintenance. Most manufacturers recommend having your watch pressure-tested by an authorized service and repair facility every year or every two to three years. They may replace dry or loose gaskets with new ones that have been well-lubricated.

Proper care will prevent your watch from losing water resistance between servicings. While you’re in the water, it’s best to not twist the crown or press any buttons on your watch. If you wear your watch in saltwater or heavily chlorinated pools, make sure you rinse it off afterwards with fresh water. If your watch has a rotating bezel, give it a couple turns while rinsing to prevent any buildup of salt or other chemicals that can cause gasket degradation.

When you treat your water-resistant watch with the right amount of care and use it only in its recommended conditions, it will keep ticking for years to come.

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