What's the biggest standard tank size?

[SCUBAholicEd]

Yes they are pos at the end of a dive by 2.35 lbs. Here are the specs:

Faber 149 Cubic Foot High Pressure Steel Tank FX Series

• DIAMETER: 8.02 inches
• LENGTH: 29.53 inches
• WEIGHT EMPTY: 46.9 lbs.
• BUOYANCY FULL: - 9.41 lbs.
• BUOYANCY EMPTY: 2.35 lbs.

Heiser tanks are composit, so they need to be thicker for the pressure and makes them very heavy. They are used alot by firefighters. I wouldn't recomend them for diving. As for the story of the idiots that killed them selves using big tanks. Drawin was right about how they tend to take them selves out of the gean pool. We all should test our gear in shallow water first, learn how to ditch weight etc, etc before jumping into water so deep you get bent being a dirt dart. If we all simply practice the most simple rules we learned in our basic training, use a little common sense, test and practice our new gear, all will go right.
A few common sense rules here; your BC should have enought lift to handle your equipment weight. Practice ditching your weight. Test to see if you have the power to SWIM you and your gear [after dumping weight] to the surface with out inflateing your BC. You don't have to have the ability to do this. But the knowledge of if you can or can't is good to know. Think of these things and practice them BEFORE you have a problem. Then if and when you do, you'll react instead of panic. It will save your life or that of a buddies. Just some food for thought.

 

[TSandM]

Well, you've gotten a lot of answers to the first half of your question.

The second half -- Is there any downside to a big tank? -- is pretty simple. They're heavy. They're harder to move around than smaller tanks, and harder to climb ladders with. The HP tanks may be difficult to get full with boat compressors, if they can't pump to 3442.

The up side? Lots of gas! If you're doing long, multi-level dives, you may find your bottom time limited more by gas supply than by no-deco time, and then a bigger tank is a nice thing to have. It also permits rational gas reserves on deeper dives.

130's trim out really well, too.

 

[oxyhacker]

My favorite tank even though I have never actually been able to find one. They were apparently spun tanks, which means the bottom had to be welded shut, which means they had to be made much thicker and heavier than a deep drawn tank like a PST or Worthington, to provide a reasonable safety margin.

Both Heiser, who made them, and Beuchat, who sold them here, seem to want to forget they ever did. BTW, they were apparently DOT 3AA - "low pressure" - tanks. Considering the difficulty of getting 4400 psi fills, most of the time the probably held 140 cf.!

The only way to get one, best I can figure, is to loot it off the remains of some poor diver who cratered into the bottom and it still there buried up to his/her waist in muck.

Heiser 190s are the biggest made in the past. 4400 psi service pressure, 31" tall, 87lbs out of water, -46lbs negative empty, -62lbs negative full. That's a serious tank right there. Interestingly enough, it's physically not an especially large tank.