Dive Tanks

[captbuddy]

I am looking for maybe three Used Dive Tanks. I have three that are made prior to 1988 and the Dive shops in Florida refuse to fill them. They say they can Hydro them but they cannot fill them. They have passed a Hydro test but the dive shops say this type of tanks have exploded before. I have been having to bring them back to Georgia each time and get them filled. I really just use them to clean the bottom of Beach Nut. Thought I'd start looking for some replacements. Any help would be appreciated.
Thanks,
captbuddy

[Boatsb]

new tanks are about $125-150. Used tanks seem to be hard to find.

[Bill Allen]

The alloys have become an issue in the 20 plus year old tanks. It's a function of how they store the gas. The can't strecth and after all these years they've reached the end. Two choices although the sons shop does sometimes have used tanks. I'd either buy new alum. 80's or really clean 72cf a better alternative in my opinion is 72's. If your really budget minded. I guess the thing that puzzles me when this comes up is they're 20 yrs old and what did they actually cost vs 20 years of use. If I was only going with a set up to clean the bottom I'd go with a non lube compressor and a long hose kill two birds with one stone. Have compressed air on board plus be able to clean the bottom.

[Genesis]

I REALLY like the old steel galvanized 72s, if you can find them.

PST made this for years (but doesn't any more) and properly-cared for these will literally last forever. They're smaller, lighter, not positive when empty (less weight on your belt), trim better and IMHO are the best "small tank" out there.

They also make incredible light doubles if you're so inclined.

And unlike the Aluminum tanks they don't explode on people.

They DO require that you feed them only clean, dry gas - but do you want to breathe anything else?

If the outer galvanizing gets chewed up due to too little rinsing you can lightly clean it with PhOsphoRic (same stuff I use to clean the H/Es on Hatts) by brushing it on to clear off the corroded zinc, wash well, then use spray galvanizing to retouch. Once you start with this you'll be stuck doing it every couple of years, but with reasonable care these tanks will literally outlast you.

[Boatsb]

The alloys have become an issue in the 20 plus year old tanks. It's a function of how they store the gas. The can't strecth and after all these years they've reached the end. Two choices although the sons shop does sometimes have used tanks. I'd either buy new alum. 80's or really clean 72cf a better alternative in my opinion is 72's. If your really budget minded. I guess the thing that puzzles me when this comes up is they're 20 yrs old and what did they actually cost vs 20 years of use. If I was only going with a set up to clean the bottom I'd go with a non lube compressor and a long hose kill two birds with one stone. Have compressed air on board plus be able to clean the bottom.

NEVER use a standard compressor for breathing air. NEVER. $150/20 years is $7.50 a year. Get a new tank and be safe.

[Bill Allen]

What Karl said, yes he's right on. As far as a compressor an oil free like I said will work just fine, just make sure your inlet gas is in a good place. Done all the time. O by the way owned a dive shop for 10 years diving for twenty. Run a dive boat and all that crap. I can assure you a non lube compresor will function fine. They are making a smaller tank again. You can aslo find some other sizes smaller the 72's also steel and nice tanks. Frankly alum is only available because the intial investment is small. They are the second worse dive cyclinders to have with only alum 100's worse choice.

[ThirdHatt]

Frankly alum is only available because the intial investment is small. They are the second worse dive cyclinders to have with only alum 100's worse choice.

Why are aluminum 100's so bad? Please explain because I would like to buy two aluminum 80's and two aluminum 100's for my wife and I to dive with.

[Bill Allen]

If you dive not just clean the boat alum requires more weight as the tank goes empty could be as much as 4 to eight pounds as the get empty they start to go posistive and float so you need more weight to overcome this. Alum 100's are even more bouyant. More like ballons then scuba tanks. Steel is a much better set up. More durable, better bouyancy (negative) and longer lasting with care. We have 72's 40 years old never a hydro or vip issue. Alum 80's are 77 c.f.steel 72's are 72 little difference in capacity. Steels lighter and requires less useless weight belt. Now if you go to a steel 85 (my favorites) you get 85 c.f. at 2400 psi. I usually fill mine to 3500 sometimes more. Standard fill pressure in europe is 3500 which as I remeber give 95 c.f. for a deeper dive I will fill to 4 or 45. No downside, tons of gas and no weight belt. Never had a steel fail a hydro. Steel just better all around. I'm sure Karl (rebreather king lol) will leap in soon and i'm sure altough we'll agree he'll do a better job of explaining it. Bill

[Genesis]

Aluminum 100s suck.

Worthington makes a nice HP Steel 100 if you want a HP (small, light) tank. So did PST before they went under, but now lots of people are having problems with them failing hydro, and they're expensive. Hmmmm perhaps there is a reason PST went down?

Faber makes a nice low-pressure (2400ish) steel tank. Their only negative is that they're cold galvanized and then painted. Therefore, you have to keep up with the external of the tank or it will rust, which of course is bad. On the other hand how hard is to examine it and touch it up once in a while?

Anyway, Aluminum 100s are horrifyingly bad when it comes to buoyancy and extra lead. Those things are water heaters and swim like 'em too. I won't dive 'em.

AL 80s are popular with dive shops for two reasons - they're cheap and if you put crap gas in them they won't rust on the inside. Oh, and since they can't/won't rust you can ignore rinsing them reasonably-well and they won't be destroyed.

On the other hand since aluminum is not ductile you can get neck cracking and then they explode, usually while you're filling them. While so far its all the older alloy tanks that are going boom (with a couple of exceptions) this may be more a function of time than alloy. My personal view is that any Aluminum tank should only be hydroed once (that is, total life of 10 years) and then turned into a gong. If you do that you won't be the guy who is missing his balls (or worse) from a tank explosion.

Of course if you are the one breathing the gas you probably care that the gas you put in there is clean and dry. The dive shop, on the other hand, doesn't, as its not THEIR pair of lungs. I've gotten several bad fills from shops, but never a bad fill from my own personal compressor. Gee, that might have something to do with who's lungs must process the gas and who's filling the tank eh?

I personally HATE aluminum tanks. I'll dive 'em if I have to, but I don't like the trim, I don't like the size, and I don't like the extra weight I have to carry on my belt. On a rebreather they're even worse as the extra positive buoyancy is REALLY annoying on a gasbag, but its quite bad even on open circuit (conventional scuba)

Remember that its not the weight of the tank - its the FULL WEIGHT of everything you have one when you go in the water that counts. The tank being a pound or two lighter doesn't matter if you have to stick 5-6 lbs of lead on your belt to compensate for it being positive, and in addition, Aluminum tanks are "light in the butt" which for most divers means they promote crappy trim and swimming position in the water.

Buy steel tanks. They're smaller, lighter, trim better, and the cost is insignificant over the life of the tank.

[ThirdHatt]

EXCELLENT advice and a real education, thank you guys! I had no idea. I have only used aluminum 80's and always assumed when I bought tanks for myself I would get two 80's for Melissa and two 100's for me so that we would run out of air at the same time as opposed to me coming up with 300-500 and her coming up with 700-900.

Stupid quetion time: If a steel tank is smaller and lighter and holds less pressure, can I last as long on the bottom? I am interested, but I would like for Melissa to have the same bottom time as she currently enjoys with aluminum 80's and I would like something akin to what I would expect out of a 100 aluminum. What should I get in steel, two 72's for her and two 85's for me? Would that net as much bottom time?

THANKS!!!