Breathing from a 30ft. snorkel

[Hank49]

I'm betting that for most people, using a half-inch hose, three feet would be about all they could muster.

That's about right. I've been siphoning water from aquaculture tanks for longer than I want to remember and the best I can do with a 3/4 inch hose is about 3.5 feet.
Back to the op, a friend of mine was doing some shallow work here in Belize and didn't know how to use scuba so he asked me if he could use a "long" snorkel. As first mentioned by others, the guy coudn't draw in air at even 3 feet depth. I posted it here about a year ago or so to get some feedback.

 

[costi]

That's low.

his friend is asking the question and no matter how "ignorant" or how naive the question, the mere act of asking it is the most important thing here. Maybe he didn't pay attention in high-school but he's paying attention now.... There is no reason to ridicule him for that! It's no wonder you gave up as a teacher!



Any point to this question that has to do with the question at hand?

R..

Thanks, Diver0001...I saw a bit of the same response last night ...not sure why.
I see about 80 posts here from people with varying theories on this snorkel thing.
That to me sounds like a discussion a true teacher would Want to see happen!
BTW.Nemrod, I've read a lot of your posts and have usually been impressed with your
participation. Gusss we all have bad days.
I also was a teacher.... of Industrial Technology, and I can honestly say that I don't think I ever did the students any injustice by not having this discussion.
And again(only because I posted it to SplitLip, I have a great respect for several of my instructors in spite of the fact they they never had me crawl doen a ladder with a long snorkel in my mouth (sounds llike a fun class exercise though)!
Bob

 

[Splitlip]

Okay, guys, I'm not buying this "can't bring up fluids" at 33".

Have none of you ever siphoned gas out of a car? I had a 6' hose for just such a purpose, and I'm pretty sure the bottom of the truck tank to the gas cap wasn't quite your 3', but it was a lot more than you seem to be talking about.

All at 1 ATA. That is the difference.

 

[Atomic_Diver]

As I recall, we are not capable of keeping lungs inflated at that depth without having air delivered at ambient pressure. The muscles are not sufficient to expand your lungs and basically all of your air would be squeezed out with no way to draw a fresh breath in. Not to mention the dead air space and CO2 build up. Previous thread on the subject: http://www.scubaboard.com/forums/do-yourself-diy/133781-breathing-underwater-7ft-diy.html

Nailed it.

 

[halocline]

Okay, guys, I'm not buying this "can't bring up fluids" at 33".

Have none of you ever siphoned gas out of a car? I had a 6' hose for just such a purpose, and I'm pretty sure the bottom of the truck tank to the gas cap wasn't quite your 3', but it was a lot more than you seem to be talking about.

You would need to measure from the surface of the gas in the tank to the top of the highest point of the siphon hose. It doesn't matter how deep the tank is. Otherwise you'd never be able to siphon water out of a lake.

Or, put another way, if you were trying to drink water out of a lake with a straw, it wouldn't matter if you had a short straw barely submerged or a very long straw all the way to the bottom, as long as your mouth was the same distance above the water.

 

[halocline]

There are stories of hard hat divers being buried in their helmets before check valves were used at the helmets air hose connection point. The check valve is the one most important piece on a surface supplied diving helmet. Something would happen at the surface like the air hose bursting and and the water pressure would literally compress the divers body into the helmet.

When I started diving, this story was the first comment made by one of my friends. Pretty morose dude, huh?

Actually I heard this too, that divers would basically get compressed right up into their hard hats. I'm sure it's not literally true; the human body is mostly incompressible water. But, the point is, if gas pressure escaped at significant depth you can bet every cubic millimeter of space in that hard hat would fill up with something, I don't want to think about what exactly.

 

[DoctorBob]

When I started diving, this story was the first comment made by one of my friends. Pretty morose dude, huh?

Actually I heard this too, that divers would basically get compressed right up into their hard hats. I'm sure it's not literally true; the human body is mostly incompressible water. But, the point is, if gas pressure escaped at significant depth you can bet every cubic millimeter of space in that hard hat would fill up with something, I don't want to think about what exactly.

There actually is a Myth Buster episode with exactly this myth tested. They took an old hard hat rig and put a "human analogue" in it. the human analogue was a plastic human skeleton with pig muscle and skin sewn around it. (It was actually pretty creepy looking) They then sent it down to 300' pressurized and abruptly cut the hose. They were filming it with underwater cameras. When they cut the pressure it was pretty gross. A lot of pig parts were forced up into the helmet. Would probably not be too pleasant if it happened to a real person.

 

[Splitlip]

Thanks, Diver0001...I saw a bit of the same response last night ...not sure why.
I see about 80 posts here from people with varying theories on this snorkel thing.
And again(only because I posted it to SplitLip, I have a great respect for several of my instructors in spite of the fact they they never had me crawl doen a ladder with a long snorkel in my mouth (sounds llike a fun class exercise though)!
Bob

No dive instructor would have you suck an over size snorkel. Nor would a flight instructor have you attempt to take off an aircraft without lifting surfaces. The instructors would (or should IMO) teach the candidate about natural dynamics.

For fun, GOOGLE, "Scuba Gas Laws, PADI."

Once again, I thought you were trolling with your initial post. But now I see you and others may not have recieved the training some of us "older" guys received.

I am surprised at the responses from some of the "experienced" divers here. Perhaps it's an indictment of the system, not you. I would not be so quick to defend your instructors for omitting these important bits of knowledge however.

I would equate that to defending my daughter's elementary school arithimetic teacher for skipping long division and handing her an HP calculator.

 

[boulderjohn]

I am surprised at the responses from some of the "experienced" divers here. Perhaps it's an indictment of the system, not you. I would not be so quick to defend your instructors for omitting these important bits of knowledge however.

I would equate that to defending my daughter's elementary school arithimetic teacher for skipping long division and handing her an HP calculator.

I do talk about this in my classes, but I really don't expect my students to retain 100% of the information I give them. When I consider all that is critical about being a safe scuba diver, the fact that students may not retain the fact that they cannot breathe off of an overly long snorkel is something I won't lose a lot of sleep over. I do want them to understand Boyle's Law and the importance of pressure changes as they go deeper, but it is not necessarily an easy transfer to go from that to long snorkels and the fact that they will not have the strength to suck in air at that depth.

I think it is better to expect people to have trouble with this and explain it to them gently than it is to insult their intelligence or their training.

 

[2degrees]

I did not read all of the post but I did read a lot of the post. I actually did try and breath from a garden hose in a pool when I was younger. IT DID NOT WORK. I could not suck in no matter how hard I tried.

Also as far as I know you can not suck water up over on atmosphere. I think in Georgia you can suck a liquid up only about 32 feet give or take. That is deep wells have pumps down in the water.