My Head Is Spinning

[GLENFWB]

I find myself in the place where I need to purchase my own tank. I have tried to read everything I can on SB to educate myself on what size/type of tank to buy and my head is spinning with all the options.

So, my question is, if you were a relatively new diver, lived in Florida so you would be doing mostly warm Gulf dives and freshwater Springs, and was going to be taking a Nitrox class in a few months.....what type/size tank would you experienced divers buy?

Don't want to re-hash an old subject so if you have a link to a previous thread that would be helpful I am open to that.

[Stu S.]

I live in Florida and dive like you. It depends upon how large a diver you are. The experience of me and my friends is that 100 cu. ft. is the size to have. Using nitrox, we tend to get low on bottom time (on the computer) and low on air at the same time using the 100. Any more air would just be more tank to haul around. A smaller cylinder would limit bottom time. 100's come in a variety of types. One of mine is a LP85 filled to 3,200 psi to get 103 cu. ft. The HP 100 is readily available, too.

Maybe this is a starting point for you.

Happy diving!

[shakeybrainsurgeon]

You need to ask yourself some basic questions: size, cost, type. The first issue is type: aluminum versus steel. Both weigh the same on land, steel weighs more in water... aluminum requires more weight in the bc or belt. Aluminum is cheaper --- you can buy an air tank AND a dedicated nitrox tank aluminum for the price of one steel tank. Aluminum is said to be more dangerous (explosion risk on filling) but new tanks make this virtually unheard of today. Aluminum also packs higher pressures. You hear a lot about relative corrosion of the two, but in practice, aluminum and steel tanks will both give you thousands of fills over a decade or two with proper care.

Diving aluminum personally makes diving on vacation easier since almost all dive ops now use aluminum, from what I hear.

For a beginning diver, a cheaper high pressure AL 80 tank is a good start.

[Doc Intrepid]

Agreed.

You likely dive in a wetsuit. It would be tough to go wrong with buying two identical aluminum 80s. Two 80s will allow you to go out on a boat and do two dives, one off each tank. They fit most divers in terms of neither knocking you in the back of the head nor on the top of your butt too badly, and most divers of all sizes can lift and carry them around without difficulties. Should you decide you'd like to double them up one day, a set of 80s makes a good set of doubles for warm ocean wetsuit divers. Plus, when that day comes, aluminum 80s are easier to O2 clean by yourself than steel tanks.

FWIW. YMMV.

[GLENFWB]

I live in Florida and dive like you. It depends upon how large a diver you are.

I am 6' 3" tall and about 235 pounds and at this stage in my diving life I am still using more air then most of the people I am diving with. I am working on that but still not there yet.

[Stu S.]

OK Glen, you are about the size of my dive pals. We all had 80's, and as steel cylinder prices got low around here, we got steel. Our reasoning was that after driving 160 miles to the dive boat in Jupiter and paying 50 bucks to get on, we wanted to get as much dive time as possible. The "AL 80" tank is really a 77, so we are now getting 30 percent more bottom time with the 100's. The whole trip was costing me about a hundred bucks, so that extra time down below was worthwhile.

My buddy Greg got two 120 cu. ft. tanks and just sold them on Ebay. I used them too, and it was like hauling half a phone pole around. He sold those for more than he paid for them and got Worthington HP 100's. Just the right size for him. I'd like Santa to drop a couple of those down my chimney.

Last Summer the DM on the boat explained how Horseshoe Reef ended in a horseshoe-shaped formation of coral and was a shark and turtle hangout. We were told we would get there in 45 min. Greg and I made it, and were the only two. All others had surfaced. We are typically the last to get back on the boat.

We recently had two dives at Boynton Beach, 60 feet for 61 minutes. When the advantages of nitrox, a computer, and the right cylinder all work together, you can do this. My daughter did this on an 80, but she weighs only 115 pounds. Even though the water temp. was 82 degrees, extra botton time can be had by wearing a light wetsuit, 3mm. We are also fortunate that as Florida divers, we need only simple equipment. No reason to "double" tanks here.

Anyway, this is what I have learned. If you want 80 cubic foot tanks, I can sell you two. Now you know why I don't use them any more.

Happy diving!

[RAD Diver]

All this advice is sound until there is a problem on the bottom. If you or your buddy have any type of OOA situation (such as a blown neck O-ring) then getting back to the surface safely could depend on your tank.
I dive LP121s when in singles usually jacked pretty good. Im 5ft7 weigh 150ish & have no problem with the weight & size. Even on a rocking & rolling boat. I do not think that I will ever double them, I have a set of LP108s that I have planned for that & also have a set of Alum 100s doubled.
If you decide HP make sure where you fill can get you to that 3500 you need. In Florida Im sure that wont be a problem. I get that in my LPs up here.:D
Good luck

[GLENFWB]

OK Glen, you are about the size of my dive pals. We all had 80's, and as steel cylinder prices got low around here, we got steel. Our reasoning was that after driving 160 miles to the dive boat in Jupiter and paying 50 bucks to get on, we wanted to get as much dive time as possible. The "AL 80" tank is really a 77, so we are now getting 30 percent more bottom time with the 100's. The whole trip was costing me about a hundred bucks, so that extra time down below was worthwhile.

and got Worthington HP 100's. Just the right size for him. I'd like Santa to drop a couple of those down my chimney.

Thanks for the insight. I am assuming (Yes, I know what happens when you assume that is why I am asking) that the HP 100's you are talking about are steel? If I am looking at the corect specs the HP 120 is 4 inches higher and 5 pounds heavier then the HP 100. The HP 100 seems to be a good balance between sizes.

Thanks for your help.

[lamont]

HP100s an Al80s are comparable in terms of weight when you look at the total mass of the diver on land. The HP100s will be about 5# heavier as a tank, but you take 5# off of your weightbelt. Its a wash when you're walking around with full gear, but its 5# heavier when you just lugging tanks around. you get an extra 30% gas though.

[Noviz]

One more consideration to confuse this... I am 6'5", 250 lbs, and had spent my short diving career using either AL80s or Steel 72s. Then my steel LP120 came into my life! Yeah, it weighs a freakin' ton... but the trim! It makes diving easier. Horizontal is automatic. And what I added in the tank came off the belt. (Caveat... this is a cold water thing, tons of neoprene in size XXXL - your resuts will vary).

[GLENFWB]

HP100s an Al80s are comparable in terms of weight when you look at the total mass of the diver on land. The HP100s will be about 5# heavier as a tank, but you take 5# off of your weightbelt. Its a wash when you're walking around with full gear, but its 5# heavier when you just lugging tanks around. you get an extra 30% gas though.

I like that perspective....I can handle the tank being heavier and I like the idea of dropping some weight while adding more gas. Okay guys...you really have me leaning toward an HP100.

[Scared Silly]

HP100s an Al80s are comparable in terms of weight when you look at the total mass of the diver on land. The HP100s will be about 5# heavier as a tank, but you take 5# off of your weightbelt. Its a wash when you're walking around with full gear, but its 5# heavier when you just lugging tanks around. you get an extra 30% gas though.

Here are some specs ...

Worthington X7-100 3442psi 24" 33lbs -2.5empty -10full
Faber FX-100 3442psi 25" 34lbs -0.5empty -8.4full
Luxfer 80 (77) 3000psi 26" 31lbs +4empty -2 full

As Lamont said you can drop some lead because in general steel cylinders are negatively bouyant when empty where as Al cylinders are not.

If you notice the HP are shorter than the Al which as pointed out may affect your trim. However, you can always add a trim weight to the cam band to help straight that out.

Just to throw one more factor into the mix. Many shops can not do HP fills. So you might find that a HP 100 at 3450 psi is in practice is at best a MP 90 at 3100psi. On the other side it was mentioned overfilling a LP cylinder - I would venture to say most shops will not do this. And it they do they are hanging their butts out in the wind if something should happen.

That said for a single cylinder the HP100 is a good choice. But you will probably be able to find used Al cylinders pretty easily which is also a good choice.

[Stu S.]

Hey Mr. Glen! Yes, we all made the move to steel. Around my part of Florida, some places will rent a steel cylinder such as a 100 or 120. Maybe you can do something similar up where you are. Noviz is right, the 120 provides big guy air. More than I need, but if you could try that and a 100, you would be the judge. I am lucky that my friends lend me things like cylinders to try out. The new Faber and Worthington "X" and "FX" cylinders appear to be the most attractive. The amount of air they hold for that size and weight, and the buoyancy characteristics seem excellent. My daughter has one of each, 80 cu. ft.

Santa... I have been good. Could I have the X-100 please?

Happy diving!