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I would not agree with how long they last, I have recently seen quite a few steel tanks fail hydro, some at their first hydro (5years old). I have 1 AL that has 4-5 hyrdro's on it now. That's not to say steels is better or worse, but longevity should not really be a concern. If you find it worth buying your own tanks, then the useful life will mean that hydro/VIP cost, no different than the your regs are the real cost of ownership, not the up front cost. Most of my tanks have 200 dives on them each, meaning cost per dive on the purchase is nothing.
I believe there is a lot more to think about for tanks than just material. You need to look at how you want to use it. I have both tanks around, some I use some for beach dives in warm water, some with drysuits and cold water, some with nitrox and longer bottom times.
Al80's are a great tank is you plan to travel for a good portion of your diving, this allows you to become familiar with the buoyancy and trim of the tank that you will be renting with you get wherever you go. unless you are a smaller framed person (think <5'5" and <120#) there is no reason to even look at other AL's, if you are the small frame, then a AL63 is a great tank. its shorter than the AL80 and people this size generally have low enough air consumption that 63 cuft is plenty for most recreational dives. its shorter size will fit your torso better and you should have better trim and comfort (but again, the AL63 is not a commonly found rental tank)
Steel- if you dive nitrox, use a drysuit, or otherwise need a little more air, the HP100 or LP95 are awesome tanks. They are about the same weight and size as the AL80 but hold more air. When you travel, you will find that steel tanks are hard to find on rental. Steel, as already mentioned has some benefits in being nearly neutral or negatively bouyant at the end of the dive.
Now, if you are a tech diver, eh... this is a beginner forum, not aimed at you.
if you could buy 2 steels and sell your al you would be able to keep consistancy, I know some of the rentals include weight with tanks around here. Since i dive locally, AL's are cheap, and alot of my friends have AL so i can borrow one or 2 easily for extras i personally would lean to AL. If your not going to travel a whole lot, diving dry adds more bouyancy to you so a steel would be better to cut required weight amount. just think of the type of diving your going to be doing in the future and decide from that. I would just advise against having one AL and one steel so you arnt adding and taking away weight each dive For vacations you could always add weight since your rentals will more than likely be AL80's the whole time your on vacation and you wouldnt be switching weights other than when you get to your vacation spot and when you get back
I was told that in Europe there is a prohibition against Alum tanks because of research evidence that Aluminum Oxide can pass through the stages of a regulator and ends in your lungs: Aluminum consumption is one of the suspected causes of Alzheimer’s. I haven’t been able to verify that there is a prohibition. I'm skeptical and wondered if anyone on this list would know.
They hold less gas than steel (typically 207 bar not 232). For the same size they're physically bigger and heavier than steel on land and in the water the things are positive (or near neutral) meaning you need to wear more lead on the tank just to sink the things. We have to use the evil 80 cubic foot things here. That works out at roughly 11.1 litres filled to 200 bar so 2220 litres of gas. My steel 12l at home is 2kg lighter, a few inches shorter, less diameter and holds about 2800 litres of gas so about 20% more in a neater, more comfortable and non buoyant package.
In the UK aluminium tanks are also more expensive than steel and more expensive to get tested. Id use Aluminium for stages but cant see a single thing in its favour vs steel for back gas.
Anyone taking offence at anything in my posts - tough. It's only an internet forum. Stop being over-sensitive. The real world isn't as warm and fuzzy.
Remember, underwater only YOU are responsible for YOUR own safety. Nobody else is.
I've got 4 tanks 3 steel 72's and 1 AL80. Two of the steels were made during the 1960's one was made in the 70's, the AL80 was made in 1980. All are hydro'd and still in use.
To avoid having to mess with my weights I just dive a little heavy. I know it's some kind of modern day diving taboo but it works for me which is all I care about. It really does come down to personal preference. I like full tanks the best.
I have 2 AL80's and 2 HP100's. The AL80's are great for warm water diving in little to no exposure protection. I can dive them with a steel plate and no weight in the summer. They are also ideal for warm water sidemount diving. The 100's are great for everything else.
According to the chart linked above, the 80's weigh a little over 37 pounds when full and the 100's weigh about 40.5. So you're carrying 3.5 extra pounds worth of tank but about 5 pounds in additional weight to sink it at the end of the dive. So a total of 1.5 pounds extra for 23% less gas with the aluminum tanks. Of course the 100's cost nearly twice what the 80's cost.
It depends upon the application. I prefer steels for my primary and secondary systems, but normally use aluminum for my decompression bottles & for travelers.
It really depends upon the type of diving your doing and what you hope to do in the future. Many of my divers in their first few years dive using 80s. Their initial dives are less than 100 ft. with a second dive usually less than 60. The aluminum gives them everything they need.
More and more are starting to go with higher capacity steel singles as it gets more of the weight off the waist and provides a bit more air for a dry suit (where you live I doubt you have this requirement). As their diving experience increases, the Al bottles will be used in a similar way as I use mine; they wont go to waste. :-)
...and was wondering if I should get another Aluminum or try a steel tank, since they appear to hold more air...
Steel cylinders do not hold more air than aluminum clyinders.
Given two cylinders, one that contains a larger volume and one that contains a smaller volume, the cylinder that contains the largest volume will contain the largest volume regardless of the composition of the cylinder.
You should be looking at the buoyancy characteristics of the cylinders (full and empty, size, weight) and make your choice accordingly.
Also, if you are planning on the extra gas that comes with a high-pressure fill of a steel cylinder, make sure you can get 3,400 PSI fills in your area.