Pressure Test
A pressure test verifies a watch's water resistance on a machine before you trust it in water. A dry test uses air pressure to detect case leaks, while a wet test submerges the watch under pressure. It is essential after any battery change or service.
At a glance
- Two methods
- Dry test (air pressure, never wets the watch) and wet test (pressure underwater, bubbles show the source)
- When to do it
- After a battery change, service, or crystal replacement, before any water contact
- Related standard
- ISO 6425 adds pressure and overpressure tests for certified dive watches
Every time a watch case is opened, its gaskets are disturbed, age, or can seat unevenly. So the only honest way to know a watch's water resistance is to test it on a machine before you put it anywhere near water.
Dry test and wet test
The two main methods complement each other:
- Dry test: the watch sits in a sealed chamber with no water and air pressure is applied; if the case flexes slightly, the device detects a micron-level leak
- Wet test: the watch is submerged in water under pressure, and escaping bubbles reveal exactly where the leak is
The dry test runs first because it never wets the watch; the wet test is used afterward to pinpoint the source of a leak.
When it matters
A pressure test matters most after the case has been opened. A battery change, servicing, or crystal replacement disturbs the gasket, so the water resistance has to be re-verified afterward. For care habits see the Maintenance category, and for watches headed underwater read our guide to the best dive watches under $500.
Examples
A watchmaker opens the case to swap your dead battery, then sets the watch in a dry tester. Because a gasket did not seat cleanly, the device flags a micron-level leak, so the watchmaker replaces the gasket and runs the test again.
Before taking an older dive watch into the water, you have it wet tested; a thin stream of bubbles at the edge of the crown shows the screw-down crown no longer seals fully.
Comparison
A dry test and a wet test serve the same goal by different routes; one detects a leak, the other locates it.
| Option A | Option B | Notes |
|---|---|---|
| Dry test | Wet test | The dry test uses air pressure and never wets the watch, which is why it goes first; the wet test submerges the watch and pinpoints the leak by showing exactly where bubbles escape. |
Related terms
Frequently asked questions
Do I need a pressure test after a battery change?
For any watch that will see water, yes. A battery change means opening the case and disturbing the gasket, so the old rating can no longer be trusted. A pressure test confirms the gasket reseated and the case still seals before you get it wet.
What is the difference between a dry test and a wet test?
A dry test applies air pressure with no water and detects a leak from the slight flexing of the case, so it runs first because it stays dry. A wet test puts the watch under pressure in water and shows the exact spot of a leak through escaping bubbles.
Is a watch marked water resistant not already tested?
The factory rating only holds when the watch is new and the case has never been opened. Gaskets age over time, shift every time the case is opened, and can be damaged by knocks. The rating is a starting point, not a guarantee, so only a current pressure test shows the real state.