What is water resistance? is most commonly asked question with regards to watches. Although manufacturers around the world are now mentioning it clearly through advertisements, material and sometimes on watch face itself, people often do not understand how water resistant their watches are when it comes to daily life activities.
Water resistance of a watch indicates how well a watch is sealed against the degree of ingression of water. Water resistance rating and degree for any watch depends upon the tests carried out in laboratory using static pressure which could be different in real life situations considering wear and tear which affects the sealing greatly.
Key to maintaining watch water resistance certainly improves if the wearer keeps it under desired conditions and gets it serviced as per regular interval recommended by the manufacturer. Let’s examine the whole topic of what is water resistance and what elements that make the watch resistant to water.
Factors that Impact Water Resistance
Water resistance of a watch depends on three following important factors largely dependent on how it is designed.
Case backs are of three types mostly and they categorize in the way they are attached to the watch. One of them is snap-on case back which is least water resistant and sealed through pressure. A small notch or cut will allow the water to seep through the case. Usually, watches with snap-on case backs have water resistant limit of 30m (meters) which may allow splashes but certainly doesn’t recommend immersion in water.
Another type is where case backs are attached with screws. These are better in quality when compared to snap on case backs. Case backs attached with screws offer a tighter seal, however a notch in the gasket would still allow water to seep through the case. Normally, watches with case backs attached with screws have water resistant limit of 100m which allows for immersion in water in shallow water.
Last and the strongest one of them is screw-in case backs which are threaded and screwed into the original case. As compared to the other two case-backs, this creates a double durable seal with the help of both threading and gasket as a seal. Practically, watches with these case backs have water resistant limit of more than 100m.
If your watch has a crown or winding knob, then this is the most significant factor in setting water resistance limit. Water can easily seep through crown stem hole due to constant movement on different positions to vary time and date. The varying pressure and movement affects the gasket overtime and decreases the resistance to water. Most commonly if crown is not inserted properly this may reduce the water resistance considerably.
Screw down crowns are the best for the purpose of water resistance as they are threaded and screwed to a threaded tube in the case. Water resistance is ensured by means of crown gasket that is compressed and seals the hole when crown gets tightened. I highly recommend the watch that has a screw down crown for swimming as it enhances the water resistance limit greatly. Although Screw down crown is never to be adjusted or wound and turned underwater just to prevent the risk of water seeping in. Screw down crown is durable and tough so it also protects against notches and knocks.
Gasket is the ring of nylon, rubber or Teflon. Generally, there are two gaskets inside a watch with one on case back and other on the crown forming a close seal to prevent the water seeping in the watch. Regular servicing of your timepiece is essential for proper care of the gaskets as they wear and tear with time which decreases the water resistance of a watch.
Water Resistance in Real Life
Watch is tested and serviced in the laboratory under set conditions e.g. keeping a fresh gasket inside a pressurized water tank with distilled water.
There are three different real life experiences which affect the water resistance limit:
- Variation in temperature affects the water resistance badly especially when the watch is taken from the hot shower and immersed in a pool or cold water.
- Variation in pressure affects the water resistance badly especially in shallow water. Displacing the water rapidly due to arm movement, will apply unnecessary pressure on the gaskets. If the gaskets are not up to the mark, they will break & let the water seep inside the watch.
- After certain time, watch starts to get old and seals start to wear off which results in decreased water resistance limit.
Water Resistance or Waterproof, Are you Confused?
Term “Water proof” has been considered as inappropriate by U.S. FTC (Federal Trade Commission). According to their judgment, a watch can never be impermeable to water at 100% because of the seals wearing off with time resulting in decline on water resistance limit. That’s why the term “Water resistant” is endorsed by FTC.
Testing Methodologies for Water Resistance
There are two water resistance tests being carried out nowadays:
In this method watch is put in a vessel or chamber with an increased air pressure. Slightest change in the case size is detected by the machine. Watch is declared unfit for water resistance if case expands, even a little.
During wet testing watch is put in a vessel filled with half water and air. Increased pressure is then applied to the watch before immersing it in water. Air pressure then slowly released after complete plunging of the watch. If bubbles start to appear during immersion, it is taken as evidence that air has penetrated into the watch proving watch is not water resistant.
ATM and BAR, what they are?
They both are units for pressure and equal to 10.3 meters height of water in a pool (Simply 1 ATM (atmospheric) = 1 Bar = 10.3 meters)
Diver’s Tool: Helium Escape Valve
Helium escape valve or Helium Release valve is a unique feature found inside some diving watches. As divers operate under great depths for a long time in diving bells under increased pressure, helium is inserted to eliminate the effect of toxic air.
Helium atoms are the smallest particles in the nature and they work their way inside the watch around the seals to equal the diving bell pressure and the air pressure inside the watch.
Problem starts when decompression stops during resurfacing which might destroy the watch crystal because of the increased pressure of helium. To avoid that Helium must escape from the watch with equal speed as compression. Mostly, Escape valves are only found in watches with water resistant limit greater than 300m.
Understanding Depth Ratings
If a watch is rated at 30m or 99ft, it doesn’t mean that watch can be plunged to the same depth. The depth ratings rated by manufacturers are impossible to be attained in practical life and can only be achieved in a laboratory under set conditions.
Water resistance Table
- 30m or 99ft……………………………………No contact with water
- 30m or 99ft- 50m or 165ft……………… A little contact as in washing hands
- 50m or 165ft- 100m or 330ft………….. Light swimming
- 100m or 330ft- 200m or 660ft……….. Normal Swimming and Snorkeling but no hot showers
- 200m or 660ft- 500m or 1650ft……….Scuba Diving and other water sports
- 500m or 1650ft+…………………………… Deep water diving
- Service your watch regularly. Run a water test every year.
- Never twist or turn the crown under water and make sure it is pushed all the way through the stem hole.
- Try not to spill any erosive chemical over the watch.
- Do not test your watch against variation in pressure.
- Do not test your watch against extreme variation in temperature.
- Never use chronograph button under water, unless mentioned by manufacturer.