Creating rock salt in a BC

[toddthecat]

Thought I would post this here just cause it was aggravating and interesting at the same time...

So I get quite a bit of used gear on eBay to incorporate into student gear for my shop. I check all gear and service it before putting into use. A while back I got a steal on three Mares Airtrim BCs. I personally use an Airtrim and needed a larger size so it was excellent. Use one, sell the other two as used gear. No biggie.

The auction showed pictures of all of them. They look almost new.

They arrive via UPS. Great day! I look over all three and they are beautiful. No wear, tear, etc. BUT, on two of the three I blow into the oral inflation hose and can't get air into them. Thinking there was an issue with the check valves I investigate further. Feeling the hoses I find obstructions. The worst one was about an inch long inside the tube and completely solid.

Assuming it to be rock salt I took the hoses off and broke the obstruction using a hammer (first time I've ever used a hammer on a BC...). This is what I got:

Three piles, three BCs.

Rinsed out the bladders and they were fine. Apparently this salt was accumulating in the bends in the hose when it was in the pocket.

My question is: how much sea water could it possibly take to create THAT much salt? I think about boiling a pot of sea water off and seeing how much salt would remain. I can't see it being such a vast amount.

Anyway, always check used gear, even if it LOOKS fine. After fixing the salt problem they were flawless. But still

 

[knowone]

Can't give you condensed pint per pound but it seems only a few dives no rinsing.
The salt rattles around wedging itself into various crevices and is added to per dive not necessarily becoming wet and is not readily dissolved with a splash anyway.

Pulled almost that amount out (still have it in a film cannister somewhere) of a virtually new ranger bladder once. Hose, inflator, and external appearance was new.

Used to have problems with perforation of thinner urethane separate bladder bcds.
That's what Aquaseal is for.

 

[vladimir]

Seawater has a salinity of about 3.5%, so 35 grams of salt per liter of water. If you have 5 grams there the prior owner left 142 milliliters of seawater to evaporate in the bc. Maybe he neglected to rinse it on the last dive, or incompletely rinsed it on several, as you might expect if it was rental gear.

 

[toddthecat]

Wow. Thanks vladimir for that info. It just seems like it would take a lot more than that to create such a huge amount of salt. Perhaps I will start a salt factory with this information I've had a few dives in sea water where I drained but didn't totally rinse the inside of my BC. Of course, I never did that and then let it sit for a long time...

 

[knowone]

Come on vladimir, I've been talkin with Yanks so much the brain has clicked back to Imperial.

 

[DevonDiver]

Perhaps you inadvertantly got involved with a drug smuggling outfit? Be wary of unexpected knocks on the door late at night...

I just can't see how that much salt could accumulate inside a hose. Each subsequent dive should have (at least partially) re-disolved any salt accumulations from previous dives... It'd be hard for a large volume to build up. Also, it would highly unlikely to re-crystalize into the large lumps shown in your photo. I've been on trips where there was no fresh water to rinse BCDs for weeks on end. What accumulates is more like dust or powder... never large crystals.

Any chance it is a cleaning agent, crushed mothballs... or drying agent?

 

[herman]

It happens, how exactly I am not sure but it does. A local repair shop has a demo BC bladder he removed from a well abused BC that has several handfulls of 1/4inch+ (6.35mm+ for those who use that wierd metric stuff ) salt crystals inside the clear bladder. Given enough volume of seawater and time, salt will form large crystals. I have seen 1 in (25.4 mm...strange system) and larger ones on Boniare where they make sea salt by evaporating seawater. It is entirely possible.

 

[rcs9250]

It happens, how exactly I am not sure but it does. A local repair shop has a demo BC bladder he removed from a well abused BC that has several handfulls of 1/4inch+ (6.35mm+ for those who use that wierd metric stuff ) salt crystals inside the clear bladder. Given enough volume of seawater and time, salt will form large crystals. I have seen 1 in (25.4 mm...strange system) and larger ones on Boniare where they make sea salt by evaporating seawater. It is entirely possible.

Ditto on that for me too. The LDS I worked at PT has a sample like that. We use it in glass to encorage rinsing the BCD out. The BCD it came from was actually cut when something heavy was set on the crystals.

Randy

 

[Cave Diver]

Come on vladimir, I've been talkin with Yanks so much the brain has clicked back to Imperial.

So THAT's what happened!!! I've been noticing how much clearer some of your posts have been recently.

 

[redacted]

Unless the BCD is leaking, you should not get any salt crystals. The formation of crystals from seawater requires evaporation.

But the bottle cap is a real puzzle.