How to choose a Dive Cylinder:
Which Tank is right for me?
Most people learn to dive using an 80 or 63 cubic foot Aluminum tank. But there are many other options when it comes to scuba cylinders.
Which cylinder is best for you depends on a few factors:
- Are you naturally negatively or positively buoyant? (do you sink easily in a pool or do you float?)
- How is your air consumption? (do you breath through a tank quickly?)
- Are you using a lot of lead while diving? (more than 12-14lbs in the ocean?)
- Are you planning on becoming a Technical Diver? (Cave, Trimix, Heliox?)
Let's start by talking about some basic information about cylinders.
Material: All scuba tanks are made of either Aluminum or Steel. Both metals have pros and cons associated with them when used for scuba diving.
Pro's of Aluminum Cylinders:
- Less expensive than Steel tanks and therefore;
- More readily available for purchase and rental
- Available in a variety of colors
Con's of Aluminum Cylinders
- Tend to become positively buoyant towards the end of the dive when the cylinder is emptier.
- Due to the thickness of the aluminum, 80 cuft cylinders actually hold 77.4 cuft of air instead of true 80 cuft.
Pro's of Steel Cylinders:
- More air for the same amount of weight
- Steel doesn't become buoyant at the end of dives
- Potentially, the diver does not need to carry as much lead
Con's of Steel Cylinders:
- Substantially more expensive than Aluminum
Size and Pressure Ratings of Cylinders:
There are many different sizes of tanks, each with different pressure ratings. Finding the right ones for you is based on experience and the type of diving you'll be doing:
- Aluminum 63 cuft = 3000 psi
- Aluminum 80 cuft = 3000 psi
- High Pressure Steel 80 cuft = 3442 psi
- Aluminum 100 cuft = 3300 psi
- High Pressure Steel 100 cuft = 3442 psi
- Low Pressure Steel 120 cuft = 2400 psi
- High Pressure Steel 120 cuft = 3442 psi
Other factors to consider when purchasing tanks:
- Dive cylinders require maintenance. There are two inspections that must be completed on all cylinders in order for them to be filled.
- Visual Plus - A yearly visual inspection to check for corrosion on both the internal surface and external surface of the cylinder. For Aluminum tanks, an eddy current test is also required.
- Hydrostatic - This inspect is require every 5 years. This test measures the expansion of the cylinder while under pressure.
- Painted tanks may look pretty at first, but rarely stay that way. Salt penetrates the painted surface of most tanks causing a bulge under the paint. During inspection, that paint must be chipped off to ensure that the salt can be cleaned off and hasn't comprised the integrity of the metal. The tanks cannot be repainted, however, leaving your tank with many bare spots without paint.
- Steel tanks are no substitute for poor buoyancy - It takes most people time and experience diving to fine-tune their buoyancy skills, which allows them to reduce the amount of lead they are diving with. Newer divers also tend to breath heavily and it takes them time to learn how to control their air consumption. Often times, newer divers are encouraged to switch to steel tanks in order to kill two birds with one stone: reduce the amount of lead they are carrying, and also have more air at their disposal. While this sounds good in theory, the reality is that steel tanks can then become a crutch of divers and can discourage the development of proper streamlining and breathing techniques. Additionally, if a diver becomes accustomed to diving with steel tanks, without the proper buoyancy skills and then travels to an area that does not have steel tanks for rent, this could impact their ability to dive comfortably.
Renting vs Buying:
One more consideration regarding tanks is Renting them versus Buying them. Which is more economical? The answer to that question is: It depends on how often you are diving. When you combine the price of the required cylinder inspections and the price for each fill, in most cases renting a cylinder is more economical because the shop then handles the inspections and your rental already includes the fill. On the other hand, owning your own tanks can be beneficial if you are doing a lot of diving (15 or more dives per year), if you are leaving the dock outside of dive shop hours, or if you are diving off your own boat.
If you do decide to purchase a new scuba tank, check with ADI first!
We'll give you free air fills for a year if you purchase a cylinder from us!