So probably stupid question... but how do you safely dive a heavy tank? You of course hear about finding dead people with their weights still on but what do you di if there's no weight to drop?
I dive in a rash guard, steel 72 and minimal weight, 4-6 pounds. 8 on a fat day
I'm not a floater... I'm looking at getting trained for nitrox and want a larger tank too take advantage of it. But looking at the #s. I might end up negative with no weight whatsoever. What's the emergency plan in that situation?
I have dived LP72s and HP120s with a rasher, 3/2, 3mm, 7mm, in freshwater and in the ocean. I currently have nine LP72s and six HP120s, from various manufacturers and eras.
It is my experience that, with valve, LP72s empty are neutral, and HP120s vary from 1 to 4 pounds negatively buoyant depending on manufacturer (PST are more nearly neutral), with some additional manufacturing variation from one cylinder to the next. I've measured empty cylinders underwater with a scale, so I believe this is accurate.
I use a steel backplate that is 6 pounds negative. In the ocean I can dive with a rasher and an HP120 and be properly weighted with no lead. In freshwater I am slightly overweighted in a 3/2 with the backplate and an HP120 even with no lead, so I avoid that combination and use the LP72s instead or the 3mm two-piece wetsuit. I typically don't dive in freshwater with just a rasher because when it's warm enough for that the viz is terrible, but when I do, I do it with the realization that I'm overweighted -- which means I will only dive over a hard bottom less than 35'.
I have established that I can swim up a full HP120 with an empty BC under the conditions I dive in.
I am prepared to ditch my kit, either at depth or at the surface, should that become necessary due to a BC failure.
I carry a large SMB that can provide up to 25# buoyancy, on almost all my dives.
On deeper dives I carry a spool of line that is useful in controlling ascent in the event of a BC failure, either in conjunction with the SMB, or by attaching it to ditched weights or ditched kit.
If I am diving with a pony cylinder, I am prepared to ditch my kit and ascend on the pony cylinder.
In those rare situations where I am diving a wall or over a black layer I don't want to go through, or over a bottom that is unsafe due to its depth or other hazards, I make sure I can become positively buoyant in the event of a BC failure by ditching lead.