Water Resistance Test

Water Resistance Test Introduction

A watch considered water resistant may come in contact with water but only to an extent. Most watches are labeled by the amount of water the the watch is safe to be emerged in. It is important to remember that a water-resistant rating given by the facturer is based upon a set of controlled conditions in a laboratory. Everyday conditions and aging of the gaskets will decrease the watch’s resistance to water over time. It is important to know that most watches are water resistant but not waterproof. Please keep in mind that once a battery had been changed, the seal protecting the watch from water will no longer be effective in protecting your watch from water. We strongly suggest that you always work well within the parameters of the manufacturer’s recommendations and have your watch tested at least once a year, or after a better change, to ensure that water will not enter the watch case. At Watch Solutions, we are able to perform a water resistance test for watches that are are suited for underwater use by the manufacturer. 
Real Life vs. Laboratory Conditions
When a watch is tested by the manufacturer it is done in a laboratory under controlled conditions. However, real life action will produce completely different results. Water temperatures in a hot-tub or a hot shower will affect the shape of the gasket seals. Especially when the watch is taken from hot temperature and immediately put into cold water (such as going from a hot-tub into a pool.)
Rapid changes in pressure such as diving into a pool, will stress the gaskets for a fraction of a second. If the gaskets are not up to specification they may rupture and cause the watch to take in water.
As the watch ages, the seals begin to erode & will no longer maintain the same water resistance levels. 

Water resistance on a watch is obtained by 3 important factors:

1. Case back:

Case back refers to how the case back is attached to the watch. Snap-on case backs are sealed by pressure and are considered the least water resistant. The slightest deformity in a case or gasket will allow water to penetrate the case. Generally, these watches will have a water resistance of 30m (99ft) – which allows for contact with water but not immersion.Case-backs attached with screws are the second level of water resistance. When a case back is attached with screws, this allows for a much tighter seal on case back. However, any deformity in the gasket will allow water to penetrate. These watches generally have a water resistance of 100m (330ft). This allows for light swimming and immersion in a pool. Screw-in case backs are threaded and then screwed into the actual case and creates a double seal by using the threading and the gasket as a seal. Diving watches with water resistant ratings greater than 100m (330ft) will usually have this type of case back.

2. Crown:

The crown is the single most important factor to ensuring water resistance. The weakest link in a watch for water to penetrate is the crown/stem hole. The stem of the crown is attached to the movement through the hole in the case’s edge. As the crown is constantly moved to different positions, from being wound and turned to correct the time, the gasket is constantly being stressed. If the crown is not pushed in all the way, water will penetrate the watch through the stem hole. Screw-Down Crowns are threaded and have a screw to a match the threaded tube in the case. A screw-down crown is essential for a watch that is intend to be submerged in water. We do not recommend swimming with a watch that does not have a screw-down crown. Please note that a watch with chronograph pushers, or a digital watch with multiple button functions, should never be pressed in water. When a button is pressed under water, the seal in the gasket and case is broken. 

3. Gaskets:

Also known as “O” rings, are made of rubber, nylon or teflon, which form watertight seals at the joints where the crystal, case back and crown meet the watch case. If the watch is a chronograph, the chronograph pushers will also have gaskets.
Gaskets eventually erode and break down over time which diminishes the water resistance of a watch. It is important to test your watch once a year for water resistance. Any competent watchmaker should have the necessary equipment to test the watch.

Water Resistance Testing Method

Water Resistance Test – The watch is placed in a chamber which is half filled with water and half air. The air pressure is increased when the watch is out of the water, then the watch is slowly immersed into the water. Once the watch is completely immersed, the air pressure is slowly released. If bubbles come out of the watch it means that air seeped into the watch prior to immersion and the watch is not water resistant. At Watch Solutions, we are able to perform this test to help us locate any water leaks in the watch case and repair/replace parts to ensure water resistance.




When buying a watch, it is important to understand the depth rating as not all watches are suitable for showers or swimming pools. (Please note: Under no circumstances should a watch be exposed to saunas or hot tubs. While a watch may be able to handle a certain amount of feet of water, the steam of a warm area can cause the gasket to expand and let condensation into the case.)
No Rating – 30m/99ftNot suited for any contact with water
30m/99ft – 50m/165ftAdvisable depth for slight splashes of water (ex. washing hands and rain droplets).
50m/165ft – 100m/330ftSufficient for light poolside swimming
100m/330ft – 200m/660ftSuitable for swimming, snorkeling and showering (do not expose to hot water)
200m/660ft – 500m/1650ftSatisfactory for impact water sports such as board diving and scuba diving
500m/1650ft +Proper depth for deep water diving.