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Waterproof tester results interpretation

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Active Member
29/8/16
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Italy
Sorry guys and mods if I open a new topic for this, but previously I probably posted this question in the wrong section so i'm trying to ask that here:

I have tried the waterproofness of my sub v7 a2824 with an home made dry pressure tester (a one with a dial indicator). It seems that it passed 8 atm because the crystal has deformed under pressure and then it seems that there was no leaks at all (the hand of the indicator remained in the same position under pressure). Unfortunately i can not try with more pressure due to safety reason; but in your opinion, can i snorkel and swim with that watch?

Thank you
 

xkqwts

Known Member
21/2/17
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Generally, for swimming it should pass 10atm, so an 8atm limit is actually pretty pointless. The other thing is that the dry test result may not be reliable, wet testers exist for a reason.

So a) just take it to a watch shop in the mall that sells the usual fashion watches, they will never recognize a rep. b) Don't give a fuck and just go swimming, if the seals are properly greased and tightened it will survive ;)
 

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Active Member
29/8/16
302
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Italy
Generally, for swimming it should pass 10atm, so an 8atm limit is actually pretty pointless. The other thing is that the dry test result may not be reliable, wet testers exist for a reason.

So a) just take it to a watch shop in the mall that sells the usual fashion watches, they will never recognize a rep. b) Don't give a fuck and just go swimming, if the seals are properly greased and tightened it will survive ;)

Thank you,
Yes i know, but the pool filter that i have used for the body of the tester is rated for maximum 10atm so i'm hell scared that it will become a bomb...

Probably i will choose option B :crazy:
 

xkqwts

Known Member
21/2/17
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Just so you know, that pressure rating is very conservative. If they write 10atm on it, it survives up to 15-20 usually. But I know what you mean, no need to take the rsik for an inadvertent frag grenade ;)

You can also do a wet test easily if you already have the whole pool filter assembly. There's a big old thread about that here somewhere (don't know whether it survived the forum crash), but basically you put the watch on a hook inside, fill it halfway with water, turn the pressure up, turn the whole thing so the watch is under water and then release pressure to check if water bubbles come out. No danger at all of water getting in the watch because the inside is overpressureized.
 

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Active Member
29/8/16
302
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Italy
Just so you know, that pressure rating is very conservative. If they write 10atm on it, it survives up to 15-20 usually. But I know what you mean, no need to take the rsik for an inadvertent frag grenade ;)

You can also do a wet test easily if you already have the whole pool filter assembly. There's a big old thread about that here somewhere (don't know whether it survived the forum crash), but basically you put the watch on a hook inside, fill it halfway with water, turn the pressure up, turn the whole thing so the watch is under water and then release pressure to check if water bubbles come out. No danger at all of water getting in the watch because the inside is overpressureized.

Yes that filter before was a wet tester... i only made a "dry module" that can be fitted inside. The filter is rated to 10 atm, but the max operative pressure is 7atm (i don't know what it means but it's reported on the box).
But one more thing... if the air can't enter inside the watch under pressure, for the water should not it be even harder? :search:
 

xkqwts

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21/2/17
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True, air enters the watch easier than water. But the problem is in the way you measure it - while the bubbles under water can be noticed easily, the dip in pressure from air entering the watch is miniscule since its inner volume is just around 1cm³. Let's do some math:

Suppose, for simplicity's sake, your pool filter has a volume of 1 liter and you crank the pressure up to 10atm while inside the watch it's at 1atm. Now if the seal breaks and air enters the watch, you lose 1/1000th of your pressure - a whopping 0,01 atm. At a monumeter dial where the atm scale equals around 1cm = 1atm, that's a tenth of a millimeter and even if the manometer could measure the pressure that precisely, you would never notice it. That's why the expensive dry pressure testers have a micrometer measuring the varying crystal height from deformation.

Anyway, since you wrote that you can see the crystal deforming (under the naked eye, I assume) and not blowing back up, you either have a plastic one or it's safe to take in the water :D
 

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Active Member
29/8/16
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True, air enters the watch easier than water. But the problem is in the way you measure it - while the bubbles under water can be noticed easily, the dip in pressure from air entering the watch is miniscule since its inner volume is just around 1cm³. Let's do some math:

Suppose, for simplicity's sake, your pool filter has a volume of 1 liter and you crank the pressure up to 10atm while inside the watch it's at 1atm. Now if the seal breaks and air enters the watch, you lose 1/1000th of your pressure - a whopping 0,01 atm. At a monumeter dial where the atm scale equals around 1cm = 1atm, that's a tenth of a millimeter and even if the manometer could measure the pressure that precisely, you would never notice it. That's why the expensive dry pressure testers have a micrometer measuring the varying crystal height from deformation.

Anyway, since you wrote that you can see the crystal deforming (under the naked eye, I assume) and not blowing back up, you either have a plastic one or it's safe to take in the water :D

nope, the dial indicator mesures the deformation of the crystal under pressure with a precision of 0,01mm steps.
I put the watch under the tool and i put the 0 of the scale on the hand of the indicator and i close the filter. When i inflate air i can see how the crystal deforms under pressure, it's invisible on naked eye, but is very noticeable with this precision tool. A shappire crystal fo a submariner rep can be deformed about 0,15mm under 6 atm but a plexi a lot more.
To read the pressure inside i look at the pressure indicator of the bike pump that i use to inflate the tester. It is quite simple to make and not so expensive; i paid 17 euros for the indicator and the rest is some metal scratches that i soldered together and putted on a wood base.

here's mine:
20180722_115246.jpg
 

xkqwts

Known Member
21/2/17
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Oh ok I'll take my previous post back then, it sounded like you were reading it from the pressure gauge. That assembly looks nice btw, didn't think it could be done for that little money.