Water Resistance Testing

Understanding Water Resistance in Watches

Water resistance is one of the most commonly misunderstood features on a watch. The numbers stamped on a case back or dial — 30m, 50m, 100m, 200m — describe the pressure the watch was tested to at the time of manufacture, under controlled static conditions. They do not describe how deep you can safely take the watch underwater in normal use.

A watch rated to 30 meters is generally considered splash-resistant — rain, handwashing. It is not designed for swimming. A watch rated to 50 meters can handle occasional shallow submersion. Swimming and recreational use typically requires 100 meters or more, and diving watches are generally rated to 200 meters or above with additional features to support that use.

But even a watch that was correctly rated at the time of manufacture may not maintain that rating over time. The gaskets that create the seals between case components degrade with age, exposure to heat, chemicals in sunscreens and soaps, and normal pressure variations. A watch that was once water resistant may not be any more — without any visible sign of the change.

Why Testing Matters

The most common way people discover their watch is no longer water resistant is when moisture gets inside the case. By that point, the damage has already started. Water inside a movement causes corrosion that begins quickly and can affect components throughout the caliber. Even a small amount of moisture, if not addressed immediately, can cause rust on pivots, rust on the mainspring, and spotted dial surfaces — all of which significantly complicate any repair.

Testing before exposure is the practical alternative. A water resistance test can tell you whether the seals in your watch are still holding, so you know whether it's safe to swim with it, wear it in the rain, or take it in the shower. If the seals have degraded, they can be replaced for a relatively modest cost — far less than the repair bill that follows water ingress.

How Water Resistance Testing Works

There are two primary methods used to test water resistance, and which is appropriate depends on the watch and the situation.

Dry pressure testing (also called dry air testing) subjects the closed watch case to positive air pressure and monitors for any pressure drop that would indicate a leak. It doesn't involve water, which makes it useful for a general integrity check. This method can detect most seal failures without any risk to the watch.

Wet testing involves actual water pressure in a controlled chamber. It's a more thorough test and is typically used to confirm resistance to a specific depth rating. For watches intended for swimming or diving use, wet testing provides more confidence than dry testing alone.

We use appropriate testing methodology based on your watch and its intended use, and we'll explain the result in plain terms.

Gasket Replacement

If testing reveals that a watch's seals are no longer effective, the next step is gasket replacement. Gaskets are fitted at three main points on most watches: the caseback, the crown tube, and the crystal. Each point has a different seal profile, and the replacement gasket needs to match the original specification for the seal to function correctly.

After new gaskets are fitted, the watch is re-tested to confirm that the replacement has restored the intended water resistance. We don't consider gasket work complete until the test result confirms the seals are working properly.

One important note: crown gaskets in particular can be affected by how the crown is used. Pulling the crown out to set time while the watch is wet, or screwing down a crown that isn't aligned properly, can damage or displace a gasket even when it's new. We can explain proper crown handling as part of the service visit.

When to Have Water Resistance Checked

There's no single universal answer, but some useful reference points: after any case opening (battery replacement, service work, crystal replacement), after any impact that may have affected the case back or crown, after the watch has been exposed to chemicals (solvents, cleaning products, sunscreen), and periodically if you regularly wear the watch while swimming — generally once a year or every other year depending on use frequency.

If you've noticed condensation inside the crystal, or if the dial appears to have moisture spots, the watch has already been compromised and should come in immediately rather than waiting for a routine check. Moisture inside the case needs to be addressed quickly to limit the damage to the movement and dial.

Limitations of Water Resistance

Even a properly sealed watch has limits. Sudden temperature changes — for example, going from a hot tub into cold water — can create pressure differentials that challenge gaskets. Some chemicals break down rubber and silicone gaskets faster than normal wear would. And watches with push-button chronograph crowns have additional seal points that are generally less robust than those of simple time-and-date watches.

Understanding what your watch is and isn't designed for is part of maintaining it correctly. If you're unsure, the answer is usually to test before you assume.