Why do cellphone waterproof ratings have a time limit? Example 6 meters for 30 minutes.
In: 54
It’s a procedure called osmosis.
The lower in the water you go, the higher the pressure.
Phones can’t be completely waterproof because they are still made of different components which have very small “cracks” or “fissures” between them.
Since those cracks are so small, it takes water a longer time to enter but the higher the pressure, the easier it will be for the water to enter the nearest low pressure object, that being the phone.
Edit: Osmosis was the wrong term, my bad.
Water molecules are pushed by other water molecules into spaces where there are less water molecules, i.e. inside the phone. The seals on the phone can push back these water molecules for a while. It’s like wrestling with a guy stronger than you. You can hold him back for a time but eventually you’re gonna get pushed backwards. The water pressure will eventually break the seals allowing water in. The metres part determines how much the water molecules are pushing against the seals.
It’s really difficult to make something completely watertight if it has any sort of openings (like a charging port). It can be done, but the engineering and materials required drive up the cost of production, and therefore the cost to the consumer. You could purchase a pretty much “forever” waterproof phone, but the cost would be significantly higher than whatever you paid for your phone (and would likely not be worth it – most people change phones for reasons other than water damage).
That said, we can make things that will keep water out for a good long while, but water pressure is pretty relentless and it will push water molecules into any crevice, eventually overcoming the strength of whatever is used to keep the water out. The deeper you go, the more pressure there is, and the more the force behind the water pushed into crevices. This is why a water resistance rating is a combination of depth and time – the materials and design of the seal are engineered to last only so long at a certain depth.
A lot of great answers already in the comments that explain the science of water resistance, but none that actually answer the question.
IP (ingress protection) ratings are standardized and have standardized tests to verify the device meets or exceeds the desired rating. For example, IP68 is a common rating for smart phones. The second digit represents water resistance. To have a level 8 water resistance in your IP rating, your device must remain functional after 30 minutes of immersion. Can the device last longer? Maybe! But the testing only requires 30 minutes.
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That depends on what IP rating a device have. Which they are tested against. If they are not tested against it: claim can’t be made that it’s rated for that.
A phone got ports etc, which is hard to make it fully IP rated. Most “waterproof phones are IPX7, that’s “temporary immersion”. Some phones are IPX8 now that’s “continuous immersion”.
Edit: they put a time to define just what “temporary” means, as some will OF COURSE challenge that.
IP ratings [https://www.iec.ch/ip-ratings](https://www.iec.ch/ip-ratings)
Answer: depends on what IP rating it’s tested against. And, just how “waterproof” it really is.
It claims 30 minutes because the test conditions only require 30 minutes.
However the enclosure engineering pretty much guarantees that if it can stay underwater for more than probably 10 minutes, it’s not leaking at all and can probably stay there for days. If water resistance feature is comprimised, which they usually will after a few years or months of regular use, the phone will leak water in and within 10 minutes and break soon after that, not 30 minutes.
Water resistant phones are designed under IP ratings standardrized by IEC, IPx7 is the start of immersion requirements. 7 means 1 meter under regular fresh water for at least 30 minutes.
For phone enclosures sealed by permanent or removable pressure-sensitive adhesive, those adhesives typically don’t care how long they are under water as long as the liquid they expose to is actually regular water and pressure/temperature stays within limits. Other sealing elements include rubber gaskets, and most importantly, a GoreTex-covered vent that allows air pressure to equalize but prevents liquid water ingression.
Those materials do degrade with time, like in a few years under regular use, but contact with liquid does not significantly accelerate it, like down to a few hours.
So in conclusion, the 30 minute limit isn’t relevant most of the time.
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