Pressure testing is a crucial element in ensuring that any watch is prepared for the rigorous demands of its intended use. This process is commonly performed on diving watches to ensure the seals are functioning correctly and prevent ingress of water, but can also be carried out on pilot’s watches, chronographs and many other types of timepiece.
By carrying out the test in house, at low cost and with minimal effort, you can significantly increase the chances that your newly purchased timepiece will stay looking good and running at its best over the long term.
How to pressure test a watch at home? It’s an important skill to learn how to do, particularly if you own high end expensive horological investment. And there are several good reasons why you should, too! This is a very popular topic among watch collectors and enthusiasts as well as current or aspiring watchmakers.
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What is a pressure test?
A pressure test, also known as a water resistance test, is a test that determines the water resistance of a watch. This test is performed by using an air pressure chamber, or a machine that can provide an accurate measurement of water pressure in atmospheres (ATM). 1 ATM is equal to 10 meters of water resistance. Take note that 1 meter is roughly 3.28 feet.
A watch’s water resistance is tested by placing the watch into an air pressure chamber and increasing the air pressure until the watch can no longer withstand it. The maximum air pressure tolerance the watch can handle before leaking water into its body is called its depth rating. The depth rating is measured in ATMs.
For example, if a watch leaks at 5 ATMs, then it has a depth rating of 50 meters (5 x 10 = 50). This means that this specific model can withstand pressures of up to 50 meters underwater without damaging the internal components from taking in any water.
It’s important to understand that this test only measures the maximum amount of pressure a watch can handle before taking in any water into its body; it doesn’t measure how much time it can stay underwater at said depth without getting damaged.
How to pressure test a watch at home
In the same way we need to check watches for leaks from time to time, divers should test their watches regularly too. We’ve gone over this with a professional at our local dive shop many times and have seen him use a simple machine that not only checks the watch, but tells you the exact depth the watch can withstand and whether or not it will leak.
This article is meant to show you how to perform a pressure test on your watch in order to determine if it is leaking air or water.
Watch Pressure Testing Machine
Most dive shops have a machine that looks like the one above. It is basically just an air compressor with a pressure gauge on it. To test your watch all you need to do is place it in the chamber and turn on the air compressor. The machine will slowly increase pressure until it reaches the maximum listed on your watch’s caseback (usually something like 20 ATM or 200 meters). If there are any bubbles coming out of your watch, you know it has a leak and needs service.
The vacuum test
The vacuum test is perhaps the most widely used test for water resistance. A watch is placed inside a closed, airtight chamber and then pressure is applied. If no air can enter the watch at all, it will remain watertight even if submerged at much greater depths.
This test is relatively simple, but it’s not perfect. There are several factors that can lead to poor results:
It’s entirely possible for a watch to be airtight without also being watertight. The only thing you can conclude from this test is that the watch passed it — not that it will be OK when fully submerged in water.
The vacuum test doesn’t evaluate whether the gaskets in your watch are secure. A few minutes in an airtight chamber is not enough time to determine whether your watch will remain sealed during physical activity or while exposed to temperature changes.
A vacuum test doesn’t mimic actual use of your watch in any way. If a watch passes this test, there’s no guarantee it will pass any other kind of pressure test.
The helium escape valve test
If you’re a watch collector, chances are you’re a diver or at least like the idea of having a timepiece that can go underwater with you. But how do you know if your watch is really safe to go down with? No one wants to take their Rolex or Omega Seamaster into the ocean only to have it fail and be ruined.
There’s no way to tell without opening up your watch and testing it, right? Not exactly. While that is still the best method, there are some other ways that can give you some piece of mind before taking the plunge. One of these is the helium escape valve test.
Helium escape valves were first introduced in 1967 by Doxa for their SUB 300T model and then later by Rolex for their Sea-Dweller model in 1971. The purpose of these valves was to solve a problem that professional divers were experiencing when coming up from deep dives. Professional divers often spend days diving in compression chambers, which are pressurized in order to allow them to dive deeper than they could otherwise safely do. One problem with this is that those chambers are filled with a mixture of helium and oxygen so the divers can breathe easier, but the helium molecules are actually smaller than oxygen molecules and have a tendency to,
Checking for moisture in the case
For the most part, watches are water resistant and not waterproof. This means that a watch can be submerged in water for a certain amount of time. Depending on whether your watch is designed for swimming, showering, or diving, this time will vary.
It is important to note that water resistance is not permanent and can change over time. As the seals in your watch degrade from age and exposure to the elements, the amount of water pressure they can withstand will decrease.
Fortunately, you can check whether your waterproof watch is still up to snuff. All you need is a pot of water and a kitchen scale or pressure gauge. Place a scale or pressure gauge in the bottom of a pot and fill it with water until it reaches a few inches below the rim. Submerge an empty plastic baggie (that’s big enough to fit your watch) into the pot with the scale or pressure gauge and weigh it down with some coins (this will keep it upright).
Seal your watch inside the baggie using masking tape across the crown and pushers — make sure there’s no air inside the baggie. Then submerge it into the pot and let it sit under pressure for at least five minutes. After five minutes, remove the baggie from water and carefully.
Knowing how to pressure test a watch at home is a useful skill that doesn’t require too much money or time to learn. You can even do it if you’ve never done it before, as long as you have the proper equipment. While it might not be the same as being tested by a professional, doing it yourself will help you know whether your watch can withstand everyday wear and tear. And since timepieces are expensive, it’s good to have some knowledge of simple testing techniques to make sure they’re holding up when you need them to.