How does moisture enter tanks?

[Gone for diving]

After all this posting and practical testing, we can conclude:

That if at 80ish ft you breath your tank down to 40ish psi on your gauge, (if you can read that fine on your gauge)
and sink to 100 ft because you died.
You will most likely get water in your tank, and eventually your gauge will read 50ish psi
Because of the water filling your tank,

 

[Tracy]

After all this posting and practical testing, we can conclude:

That if at 80ish ft you breath your tank down to 40ish psi on your gauge, (if you can read that fine on your gauge)
and sink to 100 ft because you died.
You will most likely get water in your tank, and eventually your gauge will read 50ish psi
Because of the water filling your tank,

Correct. So best bet is to not do that because your gauge will be full of water and your regulators will need to be serviced before use by the recovery diver.

 

[Tracy]

Exactly as expected.

Notice the little cloud of water vapor form for a second as pressure was released? That was from the cooling as the air expanded before returning to ambient temperature. I'm guessing that is a shop compressor without extensive drying and not regulated down dive air.

It is a low pressure shop compressor with very extensive cooling and filtering. It is the drive gas for the booster wall. The vapor is from the standing water in the pressure pot that I dumped out seconds before I slid the gauges in.

 

[broncobowsher]

It is a low pressure shop compressor with very extensive cooling and filtering. It is the drive gas for the booster wall. The vapor is from the standing water in the pressure pot that I dumped out seconds before I slid the gauges in.

OK. That makes sense.

 

[clownfishsydney]

Well, most of the replies to the original question have nothing to do with it. Water can only really get in via compressor (poor filtering) or getting blown in when a wet valve is connected to the compressor or if a totally empty tank is under water and valve open.

 

[GrumpyOldGuy]

Poorly maintained compressions, especially in humid air at many warm water dive locations. They may not remove all the moisture and as the the moist air cools it condenses the water to the bottom of the tank. Rental tanks are the worst option because they goo through many more cycles, the can have many 100's of cycles per year and outside of the US, the annual visual inspections may get skipped.

 

[Pavao]

I‘ve posted this before. That is about half the amount I removed from inside the cylinder, dry salt. How much sea water would produce this much salt?

Then this leads to more questions;

- If we believe the compressor is doing this
- How is the compressor pumping in SEAWATER?
- How many fills would it take to get this much seawater in?
- Why only one tank gets water when many are filled together?

- If it’s from water at the valve before filling
- Like above, how many fills would it take to get that much seawater in, even granting the full amount possible to be stored in the valve inlet?
- Similarly to compressor scenario, why only one tank from a batch of tanks with same valves and use?

- If empty tank, with open valve, submerged in seawater;
- How do we work this scenario, the tank would not only have to be empty, but also with the valve open, AND be submerged in seawater, how do you picture that happening?
- Now differently than the other scenarios, if this was true, I’d spect to see a lot of water.


In the end, I still have more questions than explanations

 

[boulderjohn]

In the end, I still have more questions than explanations

Yep.

Years ago a friend was diving the Devil's Throat in Cozumel, a deep swim-through that requires divers to invert to go down the chimney. They all reached the entrance and went in, but when they inverted, the diver behind him signaled out of air. They shared air, and the group went to the surface. On the surface, they found the tank was nearly completely full of air. They drained it and pulled the valve. When they did, they found that the steel tank had about a liter of rusty water in it, and the valve had no dip tube. The water had blocked the valve when they inverted.

Soon after that, that dive operator got its own compressor and stopped using the fill service used by the other shops.

So how does that happen? I have no idea myself.

 

[tarponchik]

Can this be just simple physics? Hot air containing some water is compressed into the tank, then condensation occurs, especially because the tank is cooled by water.

When the air is compressed the temperature initially rises, even as the volume of air – what we just saw as m3 – reduces.The air will also eventually cool. And as it cools, the amount of moisture in the air won’t change. Instead, because the compressed air has less volume, it will be unable to hold as much water vapour or condensate, resulting in condensation.

 

[Pavao]

Yep.

Years ago a friend was diving the Devil's Throat in Cozumel, a deep swim-through that requires divers to invert to go down the chimney. They all reached the entrance and went in, but when they inverted, the diver behind him signaled out of air. They shared air, and the group went to the surface. On the surface, they found the tank was nearly completely full of air. They drained it and pulled the valve. When they did, they found that the steel tank had about a liter of rusty water in it, and the valve had no dip tube. The water had blocked the valve when they inverted.

Soon after that, that dive operator got its own compressor and stopped using the fill service used by the other shops.

So how does that happen? I have no idea myself.

I’ve had a similar situation, diver complaining reg was breathing wet, very wet, specially when going down, head down, turned out tank had so much water even with the dip tube it was breathing wet.