Water in BC

[ams511]

You may want to deny physics, but it's stronger than you and I.

Submarines use compressed air to blow the water out of its ballast tanks. So compressed gas can be used to displace water. Caissons are another example of using air to hold back water.

I think the physics have something to do with water being non-compressible, so if displaced it needs to exit somewhere.

 

[dmaziuk]

What OP valve at the top?

Dunno, this is what oxycheq has on the "additional information" tab for #30 wing: "Dump the water out the OPV and Manual Inflator Valve & LP Inflator connector." No idea what OPV stands for in there or where there is.

 

[RJP]

Dunno, this is what oxycheq has on the "additional information" tab for #30 wing: "Dump the water out the OPV and Manual Inflator Valve & LP Inflator connector." No idea what OPV stands for in there or where there is.

Overfill Protection Valve... it's the butt dump.

 

[BRT]

Believe me, if the water is on top of the valve and you open the valve and put air in the BCD the water will go out first. How would the air get down through the water?

 

[buddhasummer]

Physics aside, as others have said, inflate and submerge in a body of water and find source of the leak, if it's the inflator unit just replace it or get it replaced under warranty if that applies, they are only $14. Water in the wing is not unusual, mine always has some water in it at the end of a dive. None of my Oxy wings leak and will stay fully inflated over night, I've never tried for longer. Good luck.

 

[The Chairman]

Submarines use compressed air to blow the water out of its ballast tanks. So compressed gas can be used to displace water. Caissons are another example of using air to hold back water.

I think the physics have something to do with water being non-compressible, so if displaced it needs to exit somewhere.

Believe me, if the water is on top of the valve and you open the valve and put air in the BCD the water will go out first. How would the air get down through the water?

The pressures used by subs to blow their tanks is substantially higher, they only drain from the bottom and there's no additional OPV valves higher up that allow the air to vent first. You can easily identify a diver who plays too much with their inflater/deflater as they always have a lot of water in their BC after the dive. When air is vented from a BC under water, the much, much heavier water flows down the sides at the same time air is escaping. How do you think water gets into BCs in the first place? I dive in a manner to minimize that phenomenon and teach that to my students as well.

 

[dmaziuk]

Overfill Protection Valve... it's the butt dump.

I sit corrected. "Overfill" vs "overpressure"? -- what's the difference if the fill is compressed air? But anyway, I dived in at least one BCD that had it (and the pull dump) up on the shoulder so that made me wonder about opening pressure of the protection valve vs pressure needed to push the water out of the bottom. Not necessarily in this wing, but in a BCD with a safety valve up top.

 

[RJP]

I sit corrected. "Overfill" vs "overpressure"? -- what's the difference if the fill is compressed air? But anyway, I dived in at least one BCD that had it (and the pull dump) up on the shoulder so that made me wonder about opening pressure of the protection valve vs pressure needed to push the water out of the bottom. Not necessarily in this wing, but in a BCD with a safety valve up top.

No difference. (Yes, some BCDs also have them up on the shoulder dump.)


The OPV will release air when the bladder is completely full to volume capacity. There's apparently some debate as to whether WATER will come out too.

 

[dmaziuk]

The OPV will release air when the bladder is completely full to volume capacity. There's apparently some debate as to whether WATER will come out too.

Well, if it's the only hole and the water is between it and air (on the inside) then d'uh. Unless the opening pressure it too close to bladder's failure point, in which case it could be BOOM! instead. If, OTOH, there's an open hole at the bottom and you need X psi to push the water out of it, and a safety valve that opens at Y psi at the top, will X always be less than Y?
(Also, how will a one hand clap sound? In a forest? :zen