When to buy tanks?

[inquis]

Is this redundant or are you actually asking?

Just examples, not asking.

 

[thomasj1107]

XS Scuba Faber High Pressure Steel Tank

If you are not using steel cylinders, try to use one and you will soon realize what you have been missing. Faber can offer you the most comprehensive range of cylinders for scuba diving. No other manuf

www.scuba.com

What is the difference between these “XS” Faber and just the HDG ones?

 

[Tracy]

What is the difference between these “XS” Faber and just the HDG ones?

The importer. XS brands the tanks they import. Blue steel doesn't.

 

[thomasj1107]

To break it down simply, At the same pressure, they hold the same amount of gas. If both tanks are filled to 3600 psi, you have the same volume of gas to use. The issue stems with an LP tank is rated at a lower pressure, so if filled "correctly," it holds less gas.
The reason for the two different styles has to do with costs and the DOT.
DOT regulates pressure vessels in the United States. If you want to manufacture tanks, you have a few ways to do it. One is use an established method, you make a tank that meets the requirements for a DOT-3aa pressure vessel. Submit them for testing and evaluation, and start manufacturing tanks. This gives you the ability to quickly and cost effectively manufacture tanks for sale. It also limits what you can make them out of, what wall thickness, weight for a given pressure, lots of things.
The other way is to design an exemption tank. You engineer it, submit it for testing, lots of testing, and submit a proposal for a special exemption from the DOT. They don't have to accept it, even if the tank is good. At that point, you can start making tanks, but it isn't over, you have to renew that exemption every so many years or every tank you ever made under that exemption becomes ineligble for retesting.
Exemption (HP) tanks cost more to design, produce, and keep active. They are also a better scuba tank in that you can get them filled to their rated pressure anywhere, not just a few places in the United states.

I know that is a lot, but we are just starting down this rabbit hole. If you have any more tank questions, feel free to ask.

So for the most part, if I just go randomly to shops for fills and don’t know if I’m going to be able to get an overfill, my best bet is to just go HP100 so I know I’m going to consistently get the MORE air that I’m wanting?

 

[Tracy]

So for the most part, if I just go randomly to shops for fills and don’t know if I’m going to be able to get an overfill, my best bet is to just go HP100 so I know I’m going to consistently get the MORE air that I’m wanting?

Correct. If buying new, unless the cost difference is significant, the HP tank is the right choice.
When buying used tanks, you can often find better deals on LP tanks, they have been around longer and there are more out there.
There is a lot of confusion on tank sizes and volumes, you will see a lot of it posted here.

 

[Alaskan Scuba Dude]

The question should be rephrased: when not to buy tanks? Some divers just have too many tanks when one size can serve most. Cheaper to rent if you're not diving deep and often.

 

[ajchapman]

For those of us reading this elsewhere who want to know what the equivalent tanks would be locally: HP100 and LP85 are both around 12L, with the HP100 rated for 237bar and and the LP85 for 182bar.

Here in NZ common tanks are owned 12L steel (12.2L 232bar) and rented ali 80 (11.1L 207bar).

 

[Wibble]

For those of us reading this elsewhere who want to know what the equivalent tanks would be locally: HP100 and LP85 are both around 12L, with the HP100 rated for 237bar and and the LP85 for 182bar.

Here in NZ common tanks are owned 12L steel (12.2L 232bar) and rented ali 80 (11.1L 207bar).

What's the cylinder testing regime like in NZ?

 

[Gandalf-the-Diver]

At what point/frequency of diving is buying tanks financially beneficial when considering the maintenance/upkeep of having your own vs just renting?

I knew I was going to dive a lot, when I signed up for my OW. I purchased a set of 5 yr old, Faber HP100s, rental tanks, from my LDS. I got them with a fresh vis and hydro. I also purchased a used, (but never used) 13cu Catalina pony. I upgraded my pony around dive 70, to a 30cu Catalina; and sold my 13cu to a dive friend. I still regret selling that tank. I have been diving for 23 months now and rapidly approaching 300 dives. Yr long, unlimited air fill card at my local shop, with top ups on my pony for free. Buying was my best option, right from the get go.

 

[ajchapman]

What's the cylinder testing regime like in NZ?

Visual each year, hydrostatic every second year. At least it isn't quite as bad as the annual hydro in Australia which our tank standards otherwise match.