Water Resistance

Water resistance

A watch marked “Waterproof” or “water resistant” can withstand contact with water. How much water it can withstand is usually indicated by how much pressure it can withstand. It is important to remember that this is tested in a neutral and controlled environment which does not always reflect reality. For example, use and aging will wear down the gaskets that ensure the tightness of the watch. In the worst case, water can come into contact with the movement. Therefore, it is strongly recommended to follow the manufacturer’s advice on how to use the watch, as well as to check it annually. Every competent watchmaker has the necessary equipment to check this.


The areas of the clock that must be sealed

The water resistance of a watch is usually ensured at three points.

1. The rear cover

The back cover is the cover that sits under the watch. This is where a watchmaker usually opens the watch when he has to enter the clockwork to carry out work such as e.g. battery replacement. The least waterproof type of back cover is the so-called “snap-on” back cover. Watches with this type of caseback are usually water-resistant to 30 – 100m. If your watch is water-resistant to a pressure of 30 metres, this means that it can come into contact with water, such as rain or when you wash your hands, but it should not be under water.

A watch that is 100m water resistant can be used for swimming but should not be taken deeper than just one meter under water. Watches with a back cover that is attached with screws or where the back cover itself is screwed on are usually more waterproof than “snap-on” back covers. These back covers are usually waterproof to 100-300 metres.

If the watch is waterproof to 200+ metres, it can usually be used for simple snorkelling and diving, but should not be taken deeper than 30 meters below the surface. If you are going to dive deeper than this, it is important that you use a watch that is specifically made for diving in deeper water.

2. The Crown

The other point on the watch that must be properly sealed is the crown. The crown is generally the weakest point of a watch when it comes to water resistance. The gaskets here are also exposed to much more wear and tear because you use the crown a lot to set the watch, wind the watch, etc. Here it is extremely important to make sure that the crown is pressed in properly or screwed in properly before you come into contact with water. A crown that can only be pressed in is less watertight than a crown that is screwed in. If you are going to dive, or only in deeper water than just one metre, a screw-down crown is a must.

It is important to make sure that the watch is completely dry before you start using the crown. Does the clock also have printers for e.g. chronograph or date function, it is also important to ensure that these are not pressed in contact with water – unless the manufacturer says otherwise.

3. Gaskets

Gaskets, also known as O-rings, are necessary for both the back cover, crown and the glass of the watch to be waterproof. These sit where the crown, glass or back cover is pressed against the case. They are usually made of rubber, nylon or Teflon. These seals wear and break down over time, especially with a lot of use, and it is very important to have them checked annually. Without gaskets that are in order, the manufacturer’s guarantee for water tightness does not apply.


Waterproofing in practice

As we talked about earlier, a watch is pressure tested by the manufacturer under optimal conditions. The watch is placed in a tank of still water and exposed to pressure, and the gaskets are brand new. In use, the environment is usually very different. Three things that particularly affect watches in real life are temperature changes, sudden pressure changes, and wear and tear.

1. Temperature changes

If you e.g. have a waterproof watch in a hot shower, or a hot tub, also go straight in a colder environment such as the sea or a pool, this will affect the shape of the seals and in the worst case cause water or steam to enter the watch. On a general basis, we recommend not exposing the watch to large temperature differences, or excessively hot temperatures in water (such as a shower or a steam room).

2. Sudden pressure changes

Diving into deep water will cause additional pressure on the seals in a very short period of time, and seals that are already worn may burst. We recommend that you change the gaskets before e.g. a holiday trip or just a trip to the water park if you know that you will be carrying out activities that will put extra strain on the seals.

3. Wear and tear

As gaskets are only thin rings, usually made of rubber, they wear out over time. You cannot expect a watch to be as waterproof after a year of use. We therefore recommend changing the gaskets annually if you want to be absolutely sure that the watch is as waterproof as the manufacturer has stated.


ATM or BAR

Atm is an abbreviation for “atmosphere”, which is a unit of pressure. One atmosphere is the pressure on the surface, and for every atmosphere you go up, you can go 10 meters down (underwater). But this is just theory which does not always reflect reality as explained at the top of the page. Bar is, so to speak, equal to the unit of measurement atm, but bar is more often used in Europe.


The Helium valve

A helium valve on a watch is only used at extreme depths when the diver is inside a diving watch (not a wristwatch). When the diving bell is submerged, the pressure inside increases and helium is added to the air to remove toxic gases. Since the helium molecules are so small, they also end up inside the watch. When the diving bell is raised again, the helium will disappear. It is important that the helium in the watch disappears at the same speed as the helium in the diving watch, otherwise the pressure inside the watch will build up and most often blow out the glass on the watch. Omega therefore invented a solution that allowed you to unscrew a valve on the watch that allows the helium to leak out at the same rate as it leaks out of the diving watch. Helium valves are generally only found on watches that are waterproof to over 300 metres.


Pagani Design Waterproof Watches: 3 ATM | 5 ATM | 10 ATM | 20 ATM


Water Resistance

Interpretation of water resistance

Even if a watch is stated to be water-resistant to 30 metres, this does not mean that you can plunge into the sea at the cabin and dive down to 30 meters with it. The depth stated by the manufacturer is theoretical and can only be achieved under controlled circumstances in a laboratory.

  • Not waterproof – The watch should not come into contact with water under any circumstances
  • 3 ATM – the watch may come into light contact with water such as rain and washing hands.
  • 5 ATM – Watches can withstand a splash of water, but should not be bathed or showered
  • 10 ATM – the watch can easily withstand surface swimming. But no jumping into pool!
  • 20 ATM – the watch can withstand swimming, snorkeling and showering, but not in too hot water.
  • 30 – 50 ATM – the watch can withstand water sports such as diving and simple scuba diving.
  • 50 ATM and above – the watch can withstand real deep water diving.