Quote Originally Posted by seasnake View Post
The manifold has an isolator between the tanks. I can breathe the full air supply from either reg, even if one post is shut off, or I can close the isolator and use the tanks independantly.
Manifolds are reliable, but much more efficient when used in a team configuration. You do not typically close the isolator valve unless you have a problem, and even then you do not have a truly independent system. In an independent rig you do not have to worry about a total loss of gas resulting from any single point of failure. If you are going to dive it closed, why not just dive true independents cylinders to satrt with and avoid the extra points of failure (not to mention not having a projection that can be damaged and still result in a total loss of all available gas supplies)? Every setup has its pros and cons and some are better suited to certain situations than others. The thing that really makes me laugh is when I read questions asking whether a setup is DIR or not, when the more appropriate question would be what are the merits and disadvantages of such a setup.