Choosing a steel tank to purchase

[loosenit2]

The two most important things to consider when deciding on a tank are 1. How much gas you need and 2. The buoyancy characteristics of the tank.

On how much you need you should figure out what your RMV rate is. As a newish diver I would figure you have an RMV of .75 cuft/min. That is a good planning factor. Based on that you can multiply times the ATA and estimate how long the gas will last you. For example , using HP 100s (100 cuft capacity at 3442 psi) doing a dive to 3 ATA your RMV would be 2.25 cuft/min which would give you a 44 min dive to empty. (but always plan on a gas reserve)

The second important factor is buoyancy. You want to make sure that you are weighted such that you can swim to the surface if you lose buoyancy (ie. your wing won't hold air). . The best rule I have heard is that you can swim about 10 lbs to the surface. So you want to make sure you are not more than 10lbs negative. If you are you need to have redundant buoyancy (i.e. drysuit, double bladder wing etc). The typical AL 80 is a couple lbs negative when full and 2-3 lbs positive when empty. The typical HP 100 is -8.6 lbs when full and -.6 lbs when empty. Other steel tanks weight more but have different weight characteristics.

After those two things materials and durability start to come into play. AL is much more corrosion resistant than steel. There is a reason most salt water divers use AL tanks, just sayin.

All I am saying, is that when choosing a tank look at the right things. How much gas you need and weighting to make sure you are still safe.

 

[RobPNW]

IMO no, not overkill. My rule to live by for tanks is that if it will see saltwater, it needs to be HDG (if steel) or aluminum. 2-4 dives a month is not an insignificant amount of diving. Assuming you want your tanks to last a long time, and steel tanks should last you a LONG time, than HDG is absolutely worth the extra cost initially.

Thanks. I also assume that down the road, if I resell them, it'll help that resale value. So what you said makes sense, last longer, and possibly get more for them when I sell them. Kind of pays for itself.

 

[Gone for diving]

Spend the extra 100.00
It will be worth it, plus you will have much better resale value.

Edit,
Oops for some reason didn't see your post, great minds think alike

 

[wetb4igetinthewater]

It case it hasn't been said already, DO NOT get an HP120. At your height (same as me) that long tank will make you foot heavy no matter what you do.

HP100s (or HP119s if you can find them) is what I'd recommend. Maybe even HP133s depending on your gas consumption as compared to others you dive with.

 

[RobPNW]

Compared to a typical AL80, the HP100 takes around 7lbs of lead off me without being significantly different in size. Am I reading that right? If so, this is a no brainer for me.

 

[rjack321]

Compared to a typical AL80, the HP100 takes around 7lbs of lead off me without being significantly different in size. Am I reading that right? If so, this is a no brainer for me.

that's about right,

the 100 is a little shorter and about 30% more expensive - but you do get 20% more gas.

 

[Marie13]

Compared to a typical AL80, the HP100 takes around 7lbs of lead off me without being significantly different in size. Am I reading that right? If so, this is a no brainer for me.

Correct.

And yes, the resale value on HP100 is very good. They go very quickly here in the Midwest whenever they come up.

 

[RobPNW]

Looking at some of the HP100s online and some say the tank and valve are Nitrox ready. Correct me if I'm wrong but if you wish to use Nitrox in the tank, you basically have to stick with Nitrox. In other words, if you put regular air in there, you can't go back to Nitrox correct? Or am I thinking of pure O2?

 

[Marie13]

You’re thinking of an O2 clean tank. If you will get nitrox that’s banked - aka already mixed before they fill your tank - you don’t need O2 clean tanks.

If nitrox will be mixed via partial pressure blending, aka right in your tank - then O2 clean tanks are required.

 

[loosenit2]

Looking at some of the HP100s online and some say the tank and valve are Nitrox ready. Correct me if I'm wrong but if you wish to use Nitrox in the tank, you basically have to stick with Nitrox. In other words, if you put regular air in there, you can't go back to Nitrox correct? Or am I thinking of pure O2?

The rules on this are squishy and applied differently at different locations. The SCUBA industry rule of thumb is that is you are using under 40% NITROX and not using Partial Pressure Blending the tank does not have to be O2 clean; however, not all fill stations use this rule. Some use a rule that says anything above 23.5% needs to be O2 cleaned.

Once O2 cleaned and used for nitrox you can still put air (21%) in the tank you just have to make sure the fill station is using O2 Clean air, basically an additional purifier on the fill station. Most fill stations use O2 clean air so it is not a problem. If you use non O-2 clean air in the tank the book answer is that the tank is now not O2 clean so you can't go back to filling tank with Partial Pressure Blending or using mixes above 40%.