Water Resistance

The Watch Superstore posted this on 31 Jul 2015


Water Resistance

  • Introduction to Water Resistance

  • What Makes a Watch Water Resistant?

  • Water Resistance in Everyday Life

  • Water Resistance vs. Water Proof

  • Water-Resistance testing methods

  • ATM or Bar

  • Helium Escape Valve

  • Getting to Grips With Depth Ratings

  • Water Resistant Watches - What We Recommend

Introduction to Water Resistance

Many watches are water resistant. This means that the watch can come into contact with water to a certain extent but a watch that’s able to be submerged in water in a laboratory may not resist water as effectively in a real life water immersion. That’s because over time, the watch will age and be exposed to knocks and bumps caused through everyday wear and tear. To avoid water coming into contact with the watch movement, which can often cause a watch to stop functioning, we recommend that you heed the manufacturer’s advice and take your watch to a specialist to have it checked and tested for water resistance annually.

What Makes a Watch Water Resistant?

  1. The Case Back
    There are three types of case back, snap-on, screw-in and threaded screw-in:
    Snap-on backs have the least water resistance as they are sealed only by pressure so over time, as the case gasket ages and is exposed to bumps and potentially cracks, it’s more susceptible to water penetration. Watches with this kind of back are usually able to resist water up to 30m but cannot be immersed in it.
    Backs that are screwed in offer a much tighter seal than that achieved by pressure alone and watches with this kind of back can usually resist water up to 100m. This means you could go swimming whilst you wear your watch but it’s wise to be aware that again, any fault in the gasket will mean that water can get in.
    Backs that are threaded and then screwed in to the case create a double seal for maximum water resistance. Many diving watches will have this kind of case back as it can allow for immersion deeper than 100m.

  2. The Crown
    A critical factor in making sure a watch is water resistant, the crown is used to turn the movement through a hole in the edge of the case and so each time you use it, it’s loosened and the gasket is pushed and squeezed. Any issues with this or if you forget to push it in firmly after you’ve adjusted the time, will mean that water could get inside the case and damage it.
    If you want to go swimming with your watch on, we recommend that you choose a watch with a screw-down crown. This means that it’s threaded and screwed into a tube in the case to close it and create a water-tight seal. It also protects the crown from bumps and knocks. Unless stated by the manufacturer, do not push or adjust the crown whilst the watch is under water.

  3. The Gaskets
    Forming watertight seals at critical joints on your watch, gaskets or “O” rings are made from flexible materials that can help two hard metal surfaces join together to keep water out. Teflon, rubber or nylon gaskets can erode over time but if you get your watch tested annually, you cn be made aware of any defects in these important seals.

Water Resistance in Everyday Life

Getting caught in the rain, swimming, diving, washing up, taking a hot bath; your watch goes through all kinds of rough and wet conditions, a far cry from the laboratory environment that’s used to test water resistance.

You may not realise it but hot water or even a change in water temperature can affect the shape of a gasket on your watch. In addition, a change in pressure, like what occurs when you dive into a swimming pool, can rupture the gasket if it’s not of a high enough quality. With older watches, these potential issues are even more likely as the seal is less resistant to water, having been exposed to many daily pressures, knocks and general stresses.

Water Resistance vs. Water Proof

You may wonder why we refer to watches as water resistant, rather than waterproof. This is because stating that something is waterproof, suggests that it is is completely impenetrable by water, which unfortunately, watches are not. The nature of the seals means that they will eventually deteriorate and so it is not truthful to say that a watch can be waterproof. It is more suitable that watches are termed as water resistant, if they meet the criteria outlined above.

How Water Resistance is Tested

Water resistance can be tested in two ways, the Dry Test and the Wet Test.

  • Dry Test
    The watch is placed in a high pressure chamber so that the machine can pick up variation in the case size as the pressure increases. Water resistance is approved if the case remains the same size.

  • Wet Test
    The watch is placed in a half water, half air filled chamber. When the watch is out of the water, the air pressure is raised, then the watch is slowly put into the water and the air pressure is slowly released. At this stage, bubbles escaping from the watch are a tell tale sign that the watch is not water resistant. This test can also help to find out exactly where a defect is on a watch.


BAR is a term commonly used in Europe and means that the watch is water resistant to 10m. ATM is the abbreviation for Atmosphere, an alternative term for the same unit of measurement.

Helium Escape Valve

In very deep diving situations, divers using a diving bell add helium to their tanks to remove toxins that occur in the due to the depth. As a gas with small molecules, helium seeps through seals into the watch until the air pressure in the watch is equal to that the diving bell.

Omega’s helium escape valve allows the helium to then escape faster than it comes in on watches which have a water resistance rating of more than 300m.

Getting to Grips With Depth Ratings

It’s important to understand that when a watch is rated as water resistant to 30m, it’s not suitable for immersing in 30m of water. Confusing? Allow us to explain. Essentially, what it means is that the depth rating posted by the manufacturer is based on ideal conditions in a laboratory. These conditions are never really attainable in everyday situations.

Our Guide to Water Resistance

No Rating - 30m

A watch with no rating or a rating of up to 30m is actually not recommended for wet conditions at all.

30m - 50m

Get caught in the rain and wash your hands whilst wearing a watch with this rating.

50m - 100m

Watches with this rating can be worn whilst you go swimming in a pool.

100m - 200m

You can go swimming, snorkelling and take a warm (not hot) shower with a watch that has this water resistance rating.

200m - 500m

Watches with this rating can be worn whilst you enjoy board diving and scuba diving and other impact water sports.

500m +

You can enjoy deep water diving with a watch that’s got this high water resistance rating.

The higher the water resistance rating, the deeper you can dive! As a final precaution, if you’re planning on wearing your watch in water, we highly recommend that you only do so if it has a screw-down crown.

Water Resistant Watches - What We Recommend

• Make sure your watch is tested by a specialist annually.

• Avoid showering whilst you wear your watch unless it has a water resistance rating of 100m and features a screw-down crown.

• Do not use the crown whilst you are in water.

• Unless approved by the watch manufacturer, do not operate the chronograph buttons whilst you are in water.

• Keep your watch away from sudden or extreme changes in temperature.

• Keep your watch away from sudden or extreme changes in air-pressure.

• Keep your watch away from abrasive chemicals - even the chlorine in a swimming pool can be corrosive.

• Tighten or push in the crown at all times and ensure it is closed properly prior to getting into water.


Categories: Knowledge Base