Al 80 vs HP100 useable amount of air

[johndiver999]

Thank you for all the information. It seems HP100 will be a better choice for me as I will have my own compressor. I am looking to increase air and reduce lead weights for a more comfortable diving experience.

this thread is like a bunch of drunk family members arguing stupid sheeet at Thanksgiving dinner. LOL

If you have you own compressor, fill the 100 to 4000 psi, and dive, dive, dive! I will let others argue over the liters/cf you will get.

 

[NW Dive Dawg]

I didn't read any of the responses on this thread...... but based on the title of the thread I can say with complete certainty and confidence that when properly filled to specs.......the HP 100 has more useable air than an AL80. Duh!

 

[halocline]

80 cf vs 100 those are the numbers but what is the difference in real life?


I stop at 1000 psi for safety a little more than the 600 psi stop


is this math correct?

Maybe your math is correct, but unilaterally stopping a (presumably recreational) dive at 1000PSI is not going to increase your safety in real life. It might increase your theoretical safety on a diving internet forum. But since you mentioned real life, you'll get the most out of any tank by planning your gas for the type of dive you're doing. (You probably already know this, but you did post on a discussion forum!) For shallow, easy, NDL dives I would happily breathe a tank down much lower than 1000PSI prior to surfacing (depending on the specifics of the dive) and so would 99% of real world divers.

I have owned and used both AL80s and HP100s, and I like them both fine. The buoyancy characteristic is the biggest difference. And not all HP100s are the same, so you'll want to find the numbers for the specific tank you're buying. I loved my faber FX100. It's a really versatile tank.

 

[Angelo Farina]

Why would anyone do this? The whole point of the higher pressure tank is to carry more gas.
Why would one end with the same pressure? The whole point is to reserve a certain volume of gas to breath.

Because this is what we were trained to do. In SI units, we end the dive at 100 bar and we consider the last 50 bars as the "hard reserve" you should have when you are back on the boat.
Most diving centers or diving boats use the same approach. A large diver with an higher SAC will ask for a 15 liters tank, a tiny female will be happy with a 10 liters tank.
But both must signal the DM at 100 bar that is time to thumb the dive and everyone is asked to be back on boat with at least 50 bars.
You can translate this to some fixed values in PSI (perhaps 1200 and 600, I do not know).
But in most places they just watch the SPG, they do not care how many liters is the tank (also because, in Imperial countries they simply do not know the value), nor what was the initial pressure (possibly it will be the same for all tanks, as they do not take care of filling more the tanks rated to an higher pressure - here we have tanks rated at 250 or even 300 bars, but if you want them filled to these pressures you will have to find the proper filling station, and be prepared to pay more).

 

[Richard Dayan]

Can I fill an HP100 to 4000 psi safely? I stop at 1000, not by choice but because the divemaster is overly safety conscience. The dives are 70 minutes NDL

 

[MidOH]

Yep. Test pressure is 4000. But youre not getting much more air past 3800. Risk exceeds reward.

My LDS banks 4000, not sure when they stop filling, but generally cools to 3600.

 

[inquis]

I stop at 1000, not by choice but because the divemaster is overly safety conscience

1000 psi AL80 == 900 psi HP100
Fill the HP to 3500, and I suspect some other diver will hit the ascent pressure first.

 

[MidOH]

I usually trans fill the top 600psi away from my HP's if I'm diving with al80 buds.

Eventually get a free baby doubles dive. Although it feels like a free desert punchcard at Shenanigans.

 

[Belzelbub]

Can I fill an HP100 to 4000 psi safely? I stop at 1000, not by choice but because the divemaster is overly safety conscience. The dives are 70 minutes NDL

Your reasoning for 1000 psi is constantly changing.

First, it was because your regulator was hard to breathe at lower pressure. When called ou on that the reason changed. Next it was for extra safety, presumably your choice as you added that you “always need a little extra in case something unexpected happens.” Now it’s not your choice at all, it’s the DMs fault.

If you want to end your dive at 1000 psi, just do it. No need for excuses. An HP100 will give you more time than an AL80, as long as you can get it filled to rated pressure. Not a problem in my area, but some shops can only do 3K.

 

[halocline]

Can I fill an HP100 to 4000 psi safely? I stop at 1000, not by choice but because the divemaster is overly safety conscience. The dives are 70 minutes NDL

If a divemaster on a 'normal' guided recreational dive is requiring clients to surface at 1000PSI, then you need to find another divemaster. Jeesh, this is not rocket science. Maybe there is something unusual about the environment you're diving in.