JBFG
Contributor
Oh, really, eh?
It’s the civilized way. We are not all barbarians eh.
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
Oh, really, eh?
It’s the civilized way. We are not all barbarians eh.
You know, my wife has told me for 38 years that if I did not have a job and take out the trash, I would be completely redundant. Or superfluous. So, every time I dive, I am diving with redundancy.
It’s the civilized way. We are not all barbarians eh.
Here in Italy the standard tank you can rent everywhere is 15 liters, 232 bars, H or, better, Y valve (2 independent valves).
Usually the posts accept both DIN and Yoke.
In the past, when Yoke was the standard, it was highly advisable to employ two independent first stages, as the chances to have an O-ring failure were significant.
As this event was relatively frequent, training here was including the manouvre of pulling the tank above your head in front of you, for closing quickly the valve of the failed post before all the air is lost.
But then DIN became the standard. With DIN, the risk of an O-ring failure are quite remote, and in the rare case the resulting air loss is modest.
Hence it became standard to use a single first stage and two second stages. I do not suggest to use an octopus (a crap yellow second stage), better to have two identical high end second stages, so you can safely employ a "primary donate" approach, and alternate the usage of the two regs for ensuring that they are always both fully functional.
Eliminating one of the two first stages diminishes slightly the redundancy, but makes the system lighter, simpler and cheaper, allowing to get a single, better first stage instead of two not-as-good.
Still I never rent cylinders with just one valve and post. Having two posts opens possibilities of different mountings of the first stage, and gives you some redundancy in case one valve refuses to open or starts leaking from the O-ring of the knob...
If you run doubles closed, you have independent tanks and a 'do nothing but switch to the other reg reserve'. But you have to switch regs during the dive to preserve the reserve (basically like sidemount). Yet, if small, they fill like a single tank.If you're using doubles with an open manifold you basically have one big tank, if you're not watching you SPG and run out of gas then you're in the same situation as having a single cylinder. What am I missing?
I love doubles.If you run doubles closed, you have independent tanks and a 'do nothing but switch to the other reg reserve'. But you have to switch regs during the dive to preserve the reserve (basically like sidemount). Yet, if small, they fill like a single tank.