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How do I make a 4 foot snorkel?
I want to be able to sit on the bottom of my 4 foot deep pool, and breath with my snorkel. Anyone made a longer snorkel before? I was thinking I would just get some tube the same size as my snorkel and attach it to the end, putting a small piece of "pool noodle" on the other end as a float. Suggestions and tips please.
Sorry, it won't work. There are two issues that you will run into when trying to use a snorkel that is longer than 18-24 inches - the "negative pressure" problem and the "dead air space" problem. In scuba training we don't recommend using snorkels that are longer than about 14 inches.
Human beings breathe by creating a pressure differential between the external air pressure (14.7 psi at sea level) and the air pressure inside our lungs. To inhale, we contract our diaphragm and muscles attached to the rib cage to expand the lungs. The increased volume inside the lungs causes the internal air pressure to drop and creates a "negative" air space, so when we open the airway to the external "high pressure" air it flows into our lungs to equalize the pressure. We exhale by relaxing these breathing muscles which collapses the chest cavity and squeezes air out of the lungs. This process is able to create about a 0.75 psi drop in pressure inside the lungs during an inhale, and works fine as long as the pressure surrounding our bodies is about the same as the pressure of the air we are trying to inhale which is always true when we are surrounded by air.
We run into problems trying to breathe air from the surface when we are under water. Water is much denser than air, and so water pressure increases quickly as we go below the surface. In fresh water, which pool water would be, the pressure surrounding our bodies increases 0.433 psi for every foot of water above us. At only two feet of depth, the pressure on our bodies is over 15.5 psi, which is about 0.8 psi higher than the pressure of the air at the surface. If you were to try to breathe surface air from a snorkel at that depth, you would find that you couldn't inflate your lungs enough to overcome that 0.8 psi of external pressure and so you wouldn't be able to get air to flow into your lungs. In fact, the deeper you go the more air would get squeezed OUT of your lungs if you tried to inhale.
In order to overcome this problem, the pressure of the air you are trying to breathe needs to be increased to compensate for the additional water pressure. You can't do this without an air compressor.
Now even if you WERE able to suck hard enough to get air into your lungs from a snorkel that was 4 feet long, you would then run into the 'dead air space' issue. The longer your snorkel, the larger the volume of air will fit inside it. You soon reach a point where the volume of air inside the hose is large enough that you aren't inhaling enough air volume to get through all of the air in the hose to reach the fresh air on the surface. Atmospheric air contains about 21% oxygen when we inhale it and our body metabolizes some of this oxygen to create carbon dioxide as a by-product so the air that we exhale only contains about 16% oxygen. If you couldn't breathe in enough volume through the snorkel to reach the fresh surface air, you would be rebreathing the carbon-dioxide rich exhaled air over and over. At some point you would deplete enough oxygen out of this air that there wouldn't be enough to sustain consciousness and you would black out. It would be highly unlikely that you would survive this event unless someone else was right there to help you.
So to sum up...you might as well drop the idea now. You can't beat the physics.
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