Why Learn Scuba with the Aluminum 80 Scuba Cylinder?

The aluminum 80 scuba tank (S80) has the worst buoyancy characteristics of any scuba cylinder.  It is five pounds lighter at the end of the dive when you have used up your air, which means you must have an extra five pounds of lead on your weight belt.

So why is it best to learn scuba diving using these tanks if they have the worst buoyancy characteristics?

Because they have the worst buoyancy characteristics!

If you can control your buoyancy with these tanks then you can easily switch to a steel tank with better buoyancy characteristics.

The fact is the standard aluminum 80 scuba tank is the most inexpensive to buy and maintain so it is favored by the vast majority of dive resorts all over the globe.

As a new diver be sure to learn how to deal with the standard aluminum 80 scuba tank and you will be prepared to dive anywhere in the world and be able to maintain your buoyancy even during a 15 foot safety stop with 500 PSI.  Once you have mastered the ubiquitous aluminum 80 consider a steel tank.

Why turning your scuba tank valve back 1/4 turn is unsafe

When I learned to dive I was told to always turn my tank valve back 1/4 turn.  This is no longer considered safe practice, but why?

The reason: A valve opened all the way and closed 1/4 turn is not usually dangerous, but a valve only open 1/4 turn could be a disaster.

How would you end up with a valve only open 1/4 of the way?

The scenario goes like this:

You open your tank valve all the way in preparation to dive.  A new diver you are working with, not realizing it is open, and who never learned "righty tighty, left loosey", closes your tank valve all the way and opens it 1/4 turn thinking he has opened it.  Clearly he had too much tequila or rum the night before.  On the surface during your predive safety check, you get plenty of air, your gauge reads full pressure and you go diving.  At depth you no longer can get adequate air causing a potential panic situation.

The simple solution to this problem is always open and close scuba tank valves all the way and so it is best to train all divers this way.

If the tank is all the way closed it will be caught while breathing on the surface.

Why did turning valves back 1/4 turn get so engrained in diving culture to begin with?

The answer is that early scuba valves and many industrial valves often jam so it was wise to turn them back 1/4 turn. Modern scuba valves do not require this precaution.  It is wise however never to forcefully open the valve all the way against the stop just in case.