Watch Water Resistancy testing – how to do it and what it means

Here at I was lucky enough to find a Bergeon 5555/98 watch water resistancy tester on eBay for the same price as a cheap Chinese version. I had been looking for some time at buying a Chinese model, but an original Swiss one for the same price was too good to ignore. I wanted to one for several reasons

  • Check water resistancy of older dive watches
  • Check water resistancy of watches we want to sell
  • Check water resistancy of watches we have repaired / replaced batteries
  • We like gadgets ….

Bergeon 5555 / 98 – a 3 bar wet tester

None of the Bergeon models come cheap – expect to pay around £500-£600 for a new one – anything from £250 to £450 for a pre-owned model. The model I bought was their cheapest model, the Bergeon 5555/98 certified for testing the water resistancy of watches to a pressure of 3 bar (3 ATM or about the same as 30m under water)

The first thing you might notice is that the air pressure guage is calibrated up to 6 bar but the test unit is only certified up to 3 bar. I’m not 100% certain why they’ve done that, I believe it’s just to show that the 3 bar it’s certified up to is nowhere near the limit of the pressure it can withstand? I don’t know for sure. I do know I have and regularly do test at 5 bar – 50m depth equivalent.

Depth rating – units of measure – metres, atmospheres or bar?

DEPTH is a measure of DISTANCE under water. That’s easy enough to understand – in this article we refer to depth in METRES. The other units used frequently to rate the water resistancy of a watch are BAR and ATMOSPHERES. Both these units are measures of AIR PRESSURE. 1 atmosphere = 1.01325 bar – for the sake of simplicity, we are treating them as EQUAL. At a DEPTH of 100m the static test pressure experienced by a watch is equal to 10 atmospheres / 10 bar. Watch manufacturers usually certify their watches water resistancy as follows:

  • 3 ATM – 3 bar – 30m = splash proof
  • 5 ATM – 5 bar – 50m = shower proof
  • 10 ATM – 10 bar – 100m = surface swimming, sailing & snorkelling
  • 20 ATM – 20 bar – 200m = impact water sports (surfing, kiteboarding etc) & scuba diving
  • 30 ATM – 30 bar – 300m = saturation diving (helium / mixed gas)
  • 100 ATM – 100 bar – 1000m = professional deep water diving

What’s does it all mean – real world water resistancy

Fortunately, most watch manufacturers have adopted an international standard to water resistancy. First introduced in 1990 as ISO 2281 : 1990 and now updated in to ISO 22810:2010 (more details here). Professional dive watches undertake a more rigorous test – ISO 6425. We have produced the infographic below covering the main points across all common water resistancy standards and ratings

Watch Water Resistancy Chart showing depth and relative pressure ratings with certified activities from washing hands to shower, swim, scuba and mixed gas diving

The key points to take away from this are :

  • If the watch is going to get splashed30m minimum
  • If you want to shower in a watch – 50m minimum
  • Want to swim or bath or snorkel in your watch – 100m minimum
  • Partake in scuba diving or impact water sports (surfing, kiteboarding etc) – 200m
  • Professional offshore mixed gas diving anything between 300m – 1000m

Performing a Watch Water Resistancy Wet Test

The actual tests undertaken to certify the rated water resistantcy of a watch to a particular depth are detailed and quite scientific. They involve immersion at various depths for differing times in to water at a variety of temperatures. WikiPedia has a good summary for those wanting more information. This article details how we test a watch for water resistancy up to 50m (5ATM) using our Bergeon 5555/98 wet tester.

Step 1 – Watch Water Resistancy = UNKNOWN

Assuming we have no prior knowledge of the watches watertight intergrity this is the starting point. Prior to even putting the watch in the wet tester it is essential that a close visual inspection of the watch is completed paying attention to the following:

  • Ensure the CROWN is screwed in tight (if screw crew model)
  • Check the CASEBACK is screwed on tight
  • Check the caseback for bulging gaskets. We sometimes see misaligned gaskets trapped between case & caseback when unprofessionally fitted.
  • Visually inspect the WATCH GLASS for signs of cracking

The diagram below shows the starting point. The watch has been placed in the top section of the Bergeon tester – in the AIR section only.

Test Watch is in the DRY area of the tester with no air pressure

Step 2 – pressurise the tester to 3 to 5 bar

It is now time to pressurise the tester. In the example below the tester is pressurised to 5 bar – equivalent to 50m depth under water. The watch MUST remain here for 5 minutes. This is ESSENTIAL for the test to work and also so as not to damage the watch.

Step 2(a) – GOOD WATCH – no internal air pressure change

If the watch has good water resistancy no additional air will enter the watch. The watch is well sealed meaing the air pressure INSIDE the watch case remains at 1 bar – even though the external pressure has been increased to 5 bar.

Step 2(b) – BAD WATCH – internal air pressure increases

If the watch has poor water resistancy additional air WILL enter the watch. The air pressure INSIDE the watch case may increases to as much as 5 bar (equalling the external air pressure of the test chamber) Think of this like pumping air into the watch case.

Step 3 – Plunge watch & slowly REDUCE air pressure in test chamber

Step 3(a) – GOOD WATCH – air pressure remains constant in watch case

Plunge the watch in to the water. Almost at the same time slowly start releasing the air from the pressure release valve. As the air pressure in the test chamber is reduced any air that may have been forced in to the watch case would now escape to equalise air pressure. As this watch has good water resistancy – no air entered the watch case during pressurisation (step 2) – so there is none to escape. The tester may see a few bubble release from the bezel, lug holes etc – just air that has been relocated during testing. A single bubble or two is nothing to worry about.

Step 3(a) – BAD WATCH – air pressure equalises – stream of bubbles

It’s a different picture for the badly sealed watch. As the air pressure in the test chamber is reduced air forced in to the case now escapes to equalise the air pressure between watch and test chamber. As this watch’s water resistancy is POOR – a stream of bubbles can be seen escaping from the CROWN area (in this example). As soon as this is observed it is time to REMOVE the watch from the water and STOP the test.

What to do after a FAILED water resistancy test?

A vast majority of failed water resistancy tests are down to something simple. The usual suspects are, in order of commonality, case back gasket, crown not screwed in tight, crown gasket(s) or poor fitting watch glass. Replace the necessary parts (add gasket sealant where applicable) and test again.

Video of a Bergeon 5555 / 98 Wet Tester in action

This short video shows some of the common scenarios explained in this article. The watch has purposefully been given some common water resistancy faults.