Scuba diving (or self contained underwater breathing apparatus diving) is an activity that is done for both recreational as well as work-based purposes. The main apparatus used during scuba diving is the scubatank(also known as the diving cylinder), which provides the air needed for the diver to remain underwater for longer periods of time. In this guide, the diver will learn how to choose the right scuba tank for his or her needs, as well as find out more about the features that can vary among different scuba tanks.
Introduction to Scuba Tanks
A scuba tank is a gas cylinder that contains high-pressure air that the diver uses to sustain respiration underwater. Purchasing a scuba tank requires the diver to know several things, including what type of diving the diver will be doing, his or her physical capacity, the type of material the scuba tanks are available in, and more.
Scuba tanks usually come in the 50, 70.2, 80, or 100 cubic feet air capacities. Contrary to popular belief, scuba tanks don’t contain only oxygen. They contain air in its entirety, which means they also contain nitrogen, carbon dioxide, and traces of other natural gases.
As for the basic composition, scuba tanks are made up of several key components. These components are:
The pressure vessel/canister which contains the highly pressurized air
The cylinder valve which connects the pressure vessel to the diving regulator and controls the flow of air out of the pressure vessel
The O-ring which forms the seal between the cylinder valve and the diving regulator
The wide variety of scuba tanks available is a result of the fact that their components come in varied types. There are additional components if more than one tank or component of a tank is used together as a set by the diver. However to maintain the easy understandability of this guide, the information given here will be focused on buying a single scuba tank for recreational use.
Scuba Tank Components
As mentioned, scuba tanks vary in features and usability for particular purposes because of differences in the types of components they hold. In this section, the diver will learn about the common variants of the pressure vessel and cylinder valve.
This component comes in two common compositions: aluminum and steel. Each material, when used to make up a scuba tank’s pressure vessel, has its own strengths and weaknesses.
Aluminumscubatanks are less affected by saltwater overall (steeltanks are susceptible to rust when constantly exposed to seawater). They are less durable than steel tanks, but most of the time they suffice for common use. However, because they are less durable, they are often made thicker than steel tanks, making them bigger and slightly more inconvenient; however, they do tend to be lighter in weight. This is true if the thickening up process is not heavily done; however, if an aluminum tank has been significantly thickened it can sometimes weigh more than a steel tank of the same capacity. Aluminum scuba tanks also don’t handle overfilling as well as steel tanks, and tend to cause buoyancy issues as they increase the buoyancy of the diver as the air inside them is used up. This is why they are often used when divers need extra buoyancy, or when multiple tanks are used at the same time since this will decrease the buoyancy effect. Despite all these shortcomings, aluminum scuba tanks are more readily available than steel tanks; so for a diver who wants to get used to diving with a more common type of scuba tank, an aluminum scuba tank should be chosen.
While that may be so, steel tanks offer a wide range of advantages over aluminum tanks. Steel tanks are significantly more durable and tend to be smaller than aluminum tanks of the same capacity because they don’t need to be thickened up like aluminum tanks, but can be heavier than an aluminum tank of the same size. Steel tanks also cope with overfilling better, and don’t pose the same buoyancy issue as aluminum tanks since they are more dense in nature. However, as previously mentioned, if not cared for properly, they can succumb to rusting when frequently used in sea water.
Both types of pressure vessels are viable options for divers; the choice really lies in the kind of scuba diving the tank is used for and how long the tank is kept underwater.
This component of the scuba tank is usually manipulated like a switch, where when the knob at the side of the valve is turned, it switches the air flow either on or off. Cylinder valves usually come in one of three forms: the single outlet plain valve or the Kvalve, the Yvalve, and the Hvalve. The Y and H valves are similar in function and nature with the only main difference being the shape of the valves. There are also other types of valves such as the J valve and in the past, the R valve, but these valves are no longer used widely as they pose a safety threat to the diver when not handled properly.
The K valve, or single outlet plain valve, is the simplest form of the cylinder valve, having only one outlet to connect to the regulator. It is easy to use with just one knob made of rubber or plastic that is turned to switch the diver’s air flow on and off; however, the valves require several turnings to do this. The K-valve has no reserve function which means if the valve or regulator fails, the diver has no alternative way to control the air flow of the scuba tank.
H and Y Valves
The H and Y cylinder valves on the other hand have two outlets that can be connected to two different regulators. Since this is the case, if any one regulator fails to function properly, the diver can just switch off the valve that connects to that regulator and continue using the scuba tank by manipulating the remaining valve and regulator. Y and H valves are especially useful if the diver is going to be in deep or cold waters where the diver’s safety can be compromised significantly if something goes wrong with the air flow.
Again, as with the pressure vessel, the type of cylinder chosen depends entirely on what the diver requires for his or her particular diving needs.
Scuba Tank Purchase Decision Checklist
When purchasing scuba tanks, the diver needs to consider the diving technicalities, the diver’s physical needs, and the diver’s budget. Buying the right scuba tank is important because buying the incorrect tank could not only inconvenience the diver, it could even cause him/her trouble in the water.
The choice of an appropriate scuba tank varies depending on several factors such as how long a diver usually stays in the water, if extra buoyancy is an issue, the location of the dive point, and so on. When diving for longer periods of time, the diver needs a scuba tank with a higher capacity as otherwise he or she will run out of air before the dive is completed. If the diver is a novice and would prefer not to deal with buoyancy issues, then he or she would be happier buying a steel cylinder instead of a aluminum one.
The location where the diver frequently dives is an important factor in determining the right scuba tank to purchase. Scuba tanks with dual outlet valves are the better choice for those who swim in deeper and colder waters. A heavier scuba tank will also be more appropriate for this purpose so that the diver can go deeper into the water without having to fight the buoyancy of the scuba tank as air is used up.
A diver who is lighter in weight may not be able to comfortably use a heavier scuba tank, so efforts should be made to choose a scuba tank that is not too heavy for the individual diver. Not only that, the diver should consider how much air he or she really needs when scuba diving. Men may need more than women, and a larger structured person would need more than a petite person. Likewise, an adult will need a tank of higher air capacity than a child or teen. New divers should invest in a larger capacity tank though as they will likely need more air until they got used to scuba diving. The tank should also not be too long for the person’s height, as it is not pleasant to keep knocking one’s head or buttocks on the ends of the tank.
One thing that’s worth noting is that every scuba tank should carry labels that state in which month and year the tank last underwent the visual inspection test and the hydrostatic test. This is because it is a requirement that scuba tanks be visually inspected every year and put through a hydrostatic test every five years. Without the information on the last time the tank was tested, it would be difficult to know when to carry out future tests. So, if the diver finds that a scuba tank does not carry these labels, it is best not to buy that particular tank. Also, if the scuba tank contains additional breathing gases besides regular air, it should clearly be labeled on the tank as well.
The diver should also consider his or her budget when purchasing a scuba tank. Aluminum tanks are easily found and are usually cheaper than steel tanks; however, the more features the aluminum tank has, the higher its price. Also, an aluminum tank usually last only half as long as a steel tank that is well cared for, so if the diver wants to keep his or her tank for a very long time without having to replace it, then it would be better to purchase a steel tank. In the long run, a steel tank may be the cheaper option since buyers will have to buy a few aluminum tanks compared to one steel tank in the span of 30 to 40 years.
Scuba tanks can be purchased at stores that sell diving gear, online businesses that specialize in such gear, and also on general online sales platforms like eBay. Regardless of where the scuba tank is bought, the diver must ensure that the aspects mentioned above are carefully considered before making a purchase decision.
How to Buy Scuba Tanks on eBay
If you are thinking of purchasing scuba tanks on eBay, you will be relieved to know that using eBay is quite easy. eBay is also a good place for any diver to start looking for a scuba tank simply because you can go through thousands of tanks both new and used to see which one suits your needs, without having to leave your home. The item is also shipped to you so you don’t have to leave your home to pick up the item either, unless you opt to purchase from a local seller and pick it up from the seller yourself.
To search for scuba tanks on eBay, you can either use the search box to type in "scuba tank" or a similar search term, or you can opt to search by category. Scuba tanks can be found under SportingGoods, in the WaterSports section. From there, you can select SCUBA & Snorkeling and further narrow down your search to Tanks.
If a listing catches your attention, click on it and more details about the listed scuba tank will be provided to you. Review the information available on the listing carefully to see if it is the tank you should buy. If you feel the scuba tank is right for you, then you can proceed to sendpaymentto the seller and the seller will then ship the product to you. Do note that you will need to sign up for an eBay account to make a purchase and registration is free. If you pay via PayPal, almost all purchases on eBay are covered by the eBayBuyerProtectionProgram.
Buying the right scuba tank is a necessary step for divers both new and old, and considering the number of choices available, making a choice can seem overwhelming. The variations in scuba tanks come in the form of their air capacity, pressure vessel composition, and the type of cylinder valve used. Understanding the pros and cons of different types of components, as highlighted in this guide, will be very helpful in guiding the diver towards the right purchase decision. As for the purchase decision itself, the diver should ensure that a scuba tank meets his or her diving needs, is right for their physical needs, has the necessary labels on it, and also is within budget.