In the summer of 2015 I had a great day at the beach with my family. We swam and built sand castles and enjoyed a great warm day on the beach.
Unfortunately I was wearing my nice watch, the one I purchased for my wedding. You can see it in the photograph at the top of the post. I made the erroneous assumption that the 100m marking on the face of the watch meant that it was waterproof to 100m. That’s not what it meant though, and had I known more about ratings on watches and wearables I would have known that.
Lucky for me the watch was easily fixable by taking it apart and drying it out and it was also lucky that the jeweller didn’t charge much for the service.
After that I decided I needed to know more about the waterproof ratings and what they mean.
Which Ratings matter?
To start this discussion we need to talk about the 2 different types of ratings you may find on your devices. First off is the IP (most often seen as an IPX notation) rating.
IP ratings stand for International Protection Marking and is also sometimes called Ingress Protection Marking. The goal of this standard was to provide more detailed information than just simply stating something was ‘waterproof’ or dust proof.
The IP ratings actually cover more than just dust or water though. An electrical socket can have an IP rating which means that kids can’t put their fingers in it during a standard child resistant test. We really just want to know about the water and dust aspects of the tests though so that’s where I’ll focus.
Once you get past IPX6 the grades no longer have a cumulative affect which means that if something is IPX6 rated it’s also assumed it’s IPX5 rated. If something is IPX7 rated it may not be true that it is also IPX5 rated which is why you make see some devices rated IPX7/5 to indicated that it’s been tested in both scenarios.
For devices you’d test IPX5 and 7 because they’re two different tests. IPX5 tests a device for intrusion of jets of water while IPX7 tests for submersion of up to 1 meter for 30 minutes. Now just because a device doesn’t say it’s IPX 5 rated as well as 7 doesn’t mean that it’s not actually capable of handling jets of water, it may mean it just wasn’t tested for jets of water and was only tested for immersion.
Now there is also an IPX scale for dust that follows the same numbering as the liquid scale mostly. Give the two different types of tests you see some devices IPX6 for dust and IPX7 ratings for liquid on devices. That means it was tested for both standards and passed both.
You can read much more detail on IP standards over at Wikipedia.
The second rating you’ll see is the ATM rating. ATM ratings deal specifically with water intrusion and ATM stands for atmospheres of pressure. There are actually two standards that cover ATM ratings.
ISO 2281 is the water-resistant standard which mainly prohibits the use of the term ‘waterproof’. Water resistant watches are generally tested at a depth of 10cm for 1 hour. There are additional tests where they change the temperature of the water a few times to make sure that no condensation happens on the watch, but again it’s in 10cm of water. Finally, they never test against ‘aged’ seals only brand new watches out of the factory. That means that your 5 year old water resistant watch may not in fact be water resistant since it was never tested and does not have to pass any long term tests to bear the water resistant marking. Also the test is performed once on a device not again so while it may perform fine with a single test it may not perform well with a second test.
The second standard is ISO 6425 and only applies to divers watches. This is really where you want to be looking in your devices if you plan to swim regularly with them. The tests for ISO 6425 compliance include tests on old seals and multiple tests with continued prolonged use and rapidly changing pressure.
For most active people you’ll need to get a watch with at least an ATM 10 rating which means it’s suitable for swimming, snorkeling, sailing and many watersports. ATM 20 means it’s suited for professional marine activity and skin diving.
If you’re really looking for a diving watch then you want a ‘Diver 100’ rating on the watch which means it’s suitable for scuba diving.
There are more ratings for things like mixed gas diving but I won’t go in to that and will direct you to the full rating on Wikipedia.
So what am I looking for in IPX and ATM ratings
Okay so what do you want in a device? If you’re going swimming with your device you want an IPX rating of at least 7 but preferably 8. IPX8 means that the device can be immersed without time limit at a depth of 3 meters. If the devices has ATM ratings then you’re looking for a minimum of ATM 10, but ATM 20 will give you the most protection without going for a fully rated diving watch. If you’re a whitewater kayaker or rafter or canyoneer then ATM 20 (or IPX8) is really where you want to look for your device to stay safe despite everything you may throw at it.
It’s worth noting that with fully rated diving watches the actual watch is pressurized which is likely to mean that you can’t just get the battery replaced at your local jeweller. You need to send the watch or device back to the manufacturer or a licensed repair facility to get a new battery.
Going back to my fancy watch I know now it’s got an ATM rating of 3 which means it’s okay in rain (but not heavy rain) and is not suitable for bathing or swimming. So I won’t make that mistake again.