Testing water resistance at home (and what does 3ATM mean?)

Thirdfox

Hey guys,

Thought this would be useful outside of the Sólás thread as a general info thread.

You might have seen I've built my own WR tester (for around 40-50 euro if I recall). Today when taking photos of the Sólás Starlight I decide to test the WR of the watch...along with a surprise.

If you want to build your own (the instructions I followed) you can find them here up on WUS:
https://forums.watchuseek.com/f6/diy-water-proof-tester-how-build-10-atm-100m-watch-water-pressure-tester-%2440-4319282-4.html

So here's the procedure:
1. Great you've built the tester!


2. Plop in the watch to be tested (5ATM Sólás Starlight in this case):


3. Add in the water so that it rests below the watch and seal up the chamber:


4. Pressurise the chamber (I used a bicycle pump) OP used an air compressor to get a 10ATM tester - my bicycle pump can hit 8ATM inside the chamber:


5. Wait...I give it around 3-5 minutes - this gives air plenty of time to enter the watch if the seals are ineffective...then release the pressure in one go using the emergency release valve:


6. Immediately tip the chamber over so that water is now covering the watch head. Observe the head carefully - if air bubbles start streaming out of the case/pushers/anywhere you have a problem with WR - immediately put the chamber upright and remove the watch (it's fine I'll explain below). Thankfully in my case the Starlight held up perfectly - no bubble streams anywhere:


7. No bubble streams? Great it means your watch passed the WR test at the particular ATM you tested it at - turn the chamber upright, check you've equalised pressure fully and remove the head to dry it.

What does WR of 5-8ATM mean? Well it means that you can safely swim, shower (and really, scuba quite a bit down below the water as long as you don't engage pushers/pull out crown) - effectively, you don't need to worry about water entering the watch doing any normal tasks. The leather strap that this dress watch is attached to may not survive a shower however

Principle of the tester:
The tester works by creating a pressure imbalance between that inside the watch and in the chamber. If seals are faulty then eventually the 8ATM of pressure will enter the 0ATM watch (that's why you give it 3-5 minutes time to allow the pressure to enter if seals are faulty).

So why is it okay to dunk a faulty watch into water without fear of destroying the movement?:
Because if the seals have failed then the watch is now pressured to 8ATM inside. When you release the pressure in the chamber it suddenly drops to 0ATM, if the seals are faulty the watch will still be pressurised to 8ATM *warning* this won't be true if the watch just doesn't have seals/has a hole/is a sieve - we are operating on the principle that this is a normal watch, not a vintage from 50 years ago with unknown history.

So with a faulty seal watch inside the watch is 8ATM, outside in the chamber it's now 0ATM this means when water (also at 0ATM inside the chamber) covers the watch air can only escape outwards due to the positive pressure difference inside - seen as a bubble stream leaking outwards - just because there are bubbles leaking out does not mean that water is entering - only when the pressure inside the watch reaches 0ATM like the chamber could it be possible that water may enter. Which is why if you notice bubble streams coming out you stop the test immediately as the watch has failed the WR test.




And here's my surprise:













This is my 3ATM WR Omega Speedmaster - it's also why I'm confident swimming/showering with it on - I check WR often and it passes with flying colours (again it was tested to 8ATM):










A "properly sealed" 3ATM watch can be taken into the swimming pool, into a shower etc. - it's only the watch manufacturers that do not seal their watches correctly at all that would need to suggest that 3ATM means "light rain" isn't supported.

So why do major watch brands say no swimming with 3/5ATM watches?

I presume because:
1) they know that people don't check WR often or have their watch serviced;
2) they don't want to tell people not to operate crowns/pushers while in a shower/swimming so might as well tell people not to swim/shower with these watches at all; and
3) liability purposes - they're just saying they don't recommend you to swim with a 3ATM watch - it does not mean a 3ATM watch (properly sealed!) will not do fine underwater.

Having said all that - my wife always takes off her 20ATM diver when showering because she's afraid water will get in

Thirdfox

Oh and on WUS someone suggested using a "bicycle shock pump" which will get up to 20ATM - so now even your divers can be tested... - though the chamber itself is safely rated to 10ATM so I won't need to go above that in all likelihood.

Cienciano

Good post. TBH, even for divers, as long they're ok for swimming, they're fine for 99.99% of owners.

Thirdfox

A watchmaker on another forum gave me this advice (which I'll be implementing) and allowed me to share it elsewhere too:

I'm not sure that I like the exact testing process you lay out.

Once you have the chamber pressurized and the let it sit a while you should slowly release the pressure down to 0 (not all in one shot) and leave the watch hanging above the water. The reason is that if the watch did leak, the sudden change in air pressure like you suggest is actually capable of blowing the crystal out of the case. If you immediately dunk the watch under the water and the crystal blows out you're in for a bad time. I've seen it happen at work with a few different brands of watches. I've also seen cases which were dry tested under pressure blow out their crystal 5 minutes after testing- a couple of times they've thrown the crystal 5-10 feet in the air. The distinct sound of the case popping apart followed a couple seconds later by the sound of the glass crystal hitting the floor is a strange thing.

So, the proper technique I would advise you to use in order to ensure maximum safety and most thorough testing would be as follows:

Put watch in chamber, above the water.

Lightly pressurize, approximately 0.5 bar, let sit for a minute or two.

Continue pressurizing to full testing pressure, let sit again for a minute or two.

Crack open the pressure and let ~0.5 bar out, then close the valve.

After 5-10 seconds, continue cycling the valve to release the pressure in 0.5-1.0 bar increments every couple of seconds.

If the watch is fine after that pressure cycling above the water, start the second phase.

Keeping the watch hanging above the water, re-pressurize the chamber to ~ 0.5 bar and let it sit for a minute.

Fully pressurize the chamber to the desired testing pressure, then let it sit again for a few minutes.

Lightly crack open the pressure to allow for a very slow de-pressurization first, then submerge the watch under water as the chamber de-pressurizes.

Large slow forming bubbles are generally air trapped below bezels, pushers, crowns, etc and are not a concern.

A stream of small bubbles (like you get from a glass of beer or champagne) indicates a leak, at which point you want to remove the watch from the water and keep slowly releasing the pressure.

If no small stream of bubbles appears your watch has passed the test.

The reason for only initially pressurizing to 0.5 bar is because it's not uncommon for a watch to not quite be sealed at normal atmospheric pressure. Maybe the caseback isn't quite screwed in fully or is slightly bent, maybe the gasket is slightly twisted, maybe there's a hair or some particle of debris across the gasket sealing surface, maybe the gasket is old and compressed and is now undersized, etc. As the pressure increases on the watch case it will compress everything together, which can be enough to cause it to fully seal up if it's borderline. If the pressure is quickly brought up to a much higher than ambient pressure from 0 it's possible you won't get enough air into the case to test for a leak before it seals. This is important because the watch spends nearly all its time at ambient atmospheric pressure, so if it's borderline whether it's sealing or not it's at a much higher risk of water or moisture getting in during daily wear. Again, at work it's not uncommon to see a watch fail a low pressure 0.5 bar test but pass a 3.0 bar test on our automatic dry testers for those reasons, which is why testing straight away to full pressure can produce misleading results. In fact for some watches we actually do an additional vacuum test to be fully thorough, and this is an even harder to pass test as once the watch goes under vacuum the case is experiencing negative pressure which effectively pulls the case apart, so any not tight seals are immediately pulled further apart and fail more quickly.