Question about my new steel tank (new to me).

[AfterDark]

Thanks everyone again.

grf88,
Can you please elaborate on what are the differences between the vintage and the modern tank? Is it about the valve and tank size?
Thanks.

No the new ones have a higher working pressure

 

[tridacna]

Curious. How much did you pay the nice old gentleman for this tank?

 

[grf88]

J-valves like you have were popular before submersible pressure gauges were in common use, they acted like a reserve when you pulled the rod down accessing the last air in the cylinder. The cylinder you have is in good condition and despite being over 50 years old has the original label in fairly good condition and that is why someone into vintage diving might appreciate it. There are plenty of old 72's still in use and are quite popular and not normally worth a great deal but this one may take someones fancy enough for them to offer you a trade.

 

[James79]

Looks like a straight thread valve from the pictures, can't tell if it's 3/4 or 1/2. I have both, so if you give an approximate measure of the neck width I'll compare mine and have an answer. If it's 3/4, Dive Gear Express has thermo valves for $35; Thermo 3442 Standalone Valves, Pro DIN/K, (typical side), Surplus | Dive Gear Express®
If it's 1/2, I'd trade you for the 1/2 straight thread K valve I have (I'm wanting a J valve for that tank!).
I've been enjoying the steel 72's quite a bit.
Respectfully
James

 

[James79]

Also, regarding your original question, I personally wouldn't hesitate to use it as an air supply for reg tuning. Granted, I would also dive it!

 

[rnln]

Wow, lot of info. Thanks everyone very much. I am going to answer all question as much as I know.

The reason why I have so many questions is because I originally want to get all gears but keep renting tank, since I need to get air each time I go anyway and tank is heavy, until I ran into this tank. The gentlemen gave it for free, just drove and picked it up. The 2 concerns I first have is if this tank carry enough air for me since I am new and breath like a cow. Second, the cost to get it (or any other used tank) up to date comparing to keep renting tank... until I read about the good things such as light weight, + rated, buoyancy and such.

James79, what is the K valve? Should I release air and take the valve off anyway to measure, since I can't use this very air in there anyway. My first thought was using this air to test and adjust my new service regulators.
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edit:
I submit before seeing your last message. Would you think the old air might be contaminated, smell, has particles (from rust or lining), etc...? Maybe I tune the regulator before I take it off.

Thanks.

 

[SandyRobinson]

Thanks everyone for the info. I hope you don't mind for some more questions.

- Is there a reason I want to keep the J valve? Since it's will be hard to breath when it's down to 200PSI, should I get rid of it? How hard it it to find another valve to fit it? I remember I have read somewhere in this board that someone point out a new decent valve cost $35. Is this my case too or diff tank diff valve?

- What is the extra portion of the valve and the SS stick for? Is it for pumping to help breathing easier when it's down to 200 PSI?

- Regarding this part from carobinsoniv mentioned above "...you can fill it to 2475 which holds about 71.2(?)cf. The compares to 78.6 cf in an AL80..."
I have read that the normal LP72 is around 24"-25" in length. This tank's length is 28.5". Does that mean it will hold more than 71.2, which also mean it will hold more or less closer to the AL80 tank?

Is the AL80 the one those scuba shops usually have for rent?

Hi rnin, some comments on your questions.
1. If it was me, I would not keep the J valve. It probably needs to be rebuilt which may run you $30. Compare that to a Thermo convertible valve sold by Dive Gear Express (south Fl) for $35. Add $10 for shipping and that is not a bad price. As mentioned earlier, make sure the threads are the same but they could tell you. A convertible valve is DIN with an insert so that you can also use a yoke valve.

2. If you use the J valve, I would remove the rod and leave the valve in the down (open) position. Then you would not have to worry about the "reserve".

3. Not sure if you are measuring to the top of the tank or the top of the valve. My USD 72s are 25.5 inches to the top of the tank and 28 to the top of the valve. Other than that, not sure I can help you there.

If you can put it into service for a reasonable amount, it will be a good value for you. For comparison purposes, my tanks had a plus rating in 66, 82, and 87 but not in 71, 04, 09, or 19. While the current year is not a plus, I am filling mine to 2400 to 2500. Not sure what your dive shop may do.

 

[rnln]

This tank measured 28.5" from tip top bottom of tank to the top of the neck/tank, not measuring the valve.
So the valve James posted above can take both DIN or Yoke? Great.
Thanks carobinsoniv

 

[AfterDark]

Wow, lot of info. Thanks everyone very much. I am going to answer all question as much as I know.

The reason why I have so many questions is because I originally want to get all gears but keep renting tank, since I need to get air each time I go anyway and tank is heavy, until I ran into this tank. The gentlemen gave it for free, just drove and picked it up. The 2 concerns I first have is if this tank carry enough air for me since I am new and breath like a cow. Second, the cost to get it (or any other used tank) up to date comparing to keep renting tank... until I read about the good things such as light weight, + rated, buoyancy and such.

James79, what is the K valve? Should I release air and take the valve off anyway to measure, since I can't use this very air in there anyway. My first thought was using this air to test and adjust my new service regulators.
---------
edit:
I submit before seeing your last message. Would you think the old air is contaminated, smell, has particles (from rust or lining), etc...?

Thanks.

OP a K valve is one without the lever on the side. Unlike a J valve that stops delivering air @300psi it delivers air until empty. These days most every divers use a K valve and some form of Submersible Pressure Gauge giving us much better air management. Don't drain the air dive it. Tank capacity is what it is, just means shorter dives. The old school of thought was that a 72 would never get you bent because it just does not the have the air to stay deep long enough. I have dove with women that puts that school of thought right out the window but, for it'll probably work for you; it does for me 50+ years of diving never been bent. I'm a underwater Hoover myself.

As far as cost v renting again how much do you dive? A hydro is about $50.00 will you rent more than $50.00 worth of tanks? My question how much is owning your own tank worth to you?

@carobinsoniv I just put a 50+year old Jvavle back in service didn't require a thing servicing valves IMO is waste of money.

 

[James79]

Would you think the old air might be contaminated, smell, has particles (from rust or lining), etc...? Maybe I tune the regulator before I take it off.

Thanks.

I wouldn't expect contamination, breathing air compressors are filtered to a ridiculous level... Only thing I would see as a notable possibility is if it had a wet fill there may be rust in the tank (slim chance and the reg's sintered filter would catch it). The tank having remained pressurized all those years means it is physically impossible for an outside contaminant to have entered.
Regarding k vs. J valve, k valves are the current standard. The names come from catalog item listings way back when (item j or item k). At least that's my understanding.
Regarding valve thread... The difference between tank necks for 1/2 or 3/4 is pretty drastic... Just hold a ruler to it and that approximation will be close enough to tell. I'll send a side by side comparison of mine shortly.
Respectfully
James