Scuba Tanks
Scuba Tanks
Most of your diving equipment, if your serious about continuing the sport, will be purchased so you will have it to use on the spur of the moment as well as becoming familiar with it by its continual use. The one item you will definitely need for diving is the tank.
Diving tanks come in a variety of sizes from about 3 to 130 cu. ft. in capacity. Which volume of air, or enriched mixture of air you want to carry on your back will depend on the depth you intend to explore as well as the depth you have to go to in order to accomplish that task
In this article let's just look at what choices you have in what is considered the standard tanks for the industry. These being the 80 cu. ft. aluminum and the 72 cu. ft. steel. Variations of these sizes will come in handy depending on how your indulgence into the sport progresses.
First of all, should you purchase either of these tanks for your personal use and should you purchase more than one? This decision will depend on just how much local diving you do compared to how much you intend to travel to far away locations.
When I first started diving in the mid-50s almost all of my diving took place within an area around the Great Lakes where I lived. For this reason, I started out with a single 72 cu. ft. steel. The reason for this was twofold, one being I couldn't afford more than one and second, that was the only type of tank on the market at that time. In addition, at that time and still today, these tanks were rated to be filled to 2,450 psi so air capacity was somewhat reduced.
Author coming aboard with single 72 on deck
As I became more proficient at diving and wanted more of an air supply, I opted for a second steel 72 along with a connection yoke to marry the two tanks together. A little more cumbersome package but once underwater it did the job.
As the years went on, my 13-year-old son entered the sport so I purchased a set of used military twin 38 cubic steel tanks for him. They were more compact and lighter but unfortunately could only be filled to 1,800 cu ft.
In the mid 70s my company relocated me to the Orlando, Florida area. My son and I canvassed the local dive shops to sign up for an off shore dive to see what the ocean was all about. Unfortunately, the shops were not too keen on us using our double hose regulators that were foreign to other divers in the group. They also were not equipped with a pressure gauge or spare regulator.
We listened to the requirements necessary to dive in the open ocean and thought it best to put our double hose regulators on the shelf and purchase the single hose models. In addition, all we had for tanks were my two steels and Gary's twin 38s. I eventually also purchased two aluminum 80s and gave Gary's tanks to a local welding shop to use with their cutting torches.
We started going out on various charter dives off the East Coast of Florida around West Palm, Jacksonville etc. Because most dives required two tanks per outing and most of the other divers were using aluminum 80s, this was the reason we decided to purchase the additional two aluminum models.
This lack of owning an aluminum 80 showed up on one of the trips off shore where I was wearing one of my original steel tanks and while swimming back to the boat ran out of air, which was no big deal to me because up North we frequently drained our tanks dry by the time we reached the surface. This was because we had no air gauge and therefore, we went with the change in breathing method which was when it appeared that we were having to suck the air out, we knew we had about 8 to 10 breaths left, which was enough to get to the surface at the depths we were diving in the lakes. Oh yes, we also paid no attention to a safety stop because it was not the practice at that time and also, we didn't have enough air capacity to stay long enough to acquire much residual Nitrogen. Crazy, no it was the rules at the time. Now we were not total neophytes, we did have the Navy Diving Tables and followed the basic charts for single and repetitive dives and the main reason I made up the double 72s was for salvage work in the marina as well as other shallow water jobs.
Now, let's get back to tanks themselves and today's selection for the diversity in diving that presents itself.
The Sport Diver
By far the most widely used tanks in sport diving are the aluminum 80 cu. ft. capacity. Even though there are various sizes on the market with capacities ranging from 3 to 100 cu. ft. These tanks are very durable if taken care of properly, by properly I mean be careful not to rough handle them so deep nicks are noticeable in them, this can be a weak point for failure. Most dive shops will not fill an aluminum tank that has noticeable rough handling marks on it.
On the other hand, steel tanks can take more of a beating due to their steel strength. The steel will rust if the galvanized coating is scraped off but can be cleaned up without harming the integrity of the metal. I can attest to this rough handling by the way we treated out single 72s back in Ohio in the 50s.
How tanks were stored on board our club boat
Aluminum tanks are resistant to internal rust. Even if a little salt water enters the valve, it should not do enough harm that can't be caught at the next VIP inspection. This is not so with the steel cylinders which are more prone to rust internally, especially in salt water. If the internal rust is not too bad, a steel tank can be what is known as "Tumbled" which is to insert a media and rotate the tank on rollers for an hour or so. This process will cost the diver anywhere from $30 to $50.
Another reason aluminum 80s are popular is that most of the dive charters and liveaboards use them. This is so all the divers in the group have the same amount of air thereby surface together. Of course, there may be a novice diver that will use their air faster than the group, but in most cases the dive charter will have one of their experienced divers accompany them for the purpose of surfacing before the rest of the group.
Now, what is the main reason the aluminum tank is more popular than the steel............price! Comparing an aluminum 80 cu. ft. tank with a steel 80 cu. ft. one, the price of the steel will be about $100 more.
Air Weighs
There are two factors when looking at any dive tank, weight and capacity. The weight of the material the tank itself is made from and the capacity, under pressure, of the air itself that also has weight. When I was required to fill an aluminum 80 tank at the shop, I would fill it in water to cool it for a better fill as well as protection if an explosion ever occurred. When first placed in the tank the aluminum 80 would float but during the fill process it would gradually sink to the bottom of the tank, proving the air had weight.
One of the down sides of an aluminum tank is because they are made from lighter material than a steel tank, they become positively buoyant when reaching empty. This requires the diver to carry additional weight so they are not in a positive condition during a safety stop.
If you are a diver that, for one reason or another, uses air faster than most of the other people on the charter, you have a few options. You could move up to an aluminum 100 which is the largest aluminum tank on the market. Unfortunately, the aluminum 100 weighs in at 40 lbs. which is getting pretty heavy to handle, both carrying to the dive and on your back. In addition, it's going to have even more positive buoyancy toward the end of the dive.
Another option for the air junkie is moving to the high-pressure steel 100. This tank has a working pressure of 3442 psi but weighs no more than an aluminum 80. What allows the steel 100 to supply more air for the diver is the additional 442 psi the tank is allowed to be filled to along with the fact that an aluminum 80 is, in reality, not an 80 cu. ft. tank but only has a 77 cu. ft. capacity. More pressure plus more capacity relates to more air for the diver. In addition, the steel still has the benefit of no buoyancy problem toward the end of the dive. Question for you is this additional capacity worth the extra $100?
Yoke and DIN Tank Valves
Another choice when purchasing a tank is what design valve will you have installed. The yoke valve has been around since the beginning and has done a pretty good job to date. About 20 years ago the industry started seeing DIN valves. These DIN valves were more widely used in the European countries but eventually became more in use in the United States.
The DIN is really not a specific name for the valve it stands for Deutsche Industrie Norm which is an industrial testing and approval agency based in Berlin, Germany. This organization is responsible for inspecting a number of products but somehow the European diving community began referring to this configuration of dive valve as DIN.
Now that you are brought up to speed on the name, let's first look at what the difference is between the regulators.
The main obvious difference is that the Yoke regulator is mounted to the tank valve by means of, to be basic, a clamp that fits over the valve and seats on the O ring mounted in the valve itself. On the other hand, the DIN regulator has a screw-in design whereby the O ring is mounted at the end of the regulator section that is inserted into the tank valve and seats against the back of the valve receptor.
Looking at the tank valves for each, you can see just how they differ in construction.
As you can see the DIN Valve is designed with internal threads to accept the DIN regulator. As mentioned before, one of the benefits, mentioned by dive shop owners, is that the O ring seal is more protected in the DIN model due to it being captured internally into the recess of the tank valve and less prone to leaking if the regulator is bumped or twisted either on the boat or during a dive. I will add a side comment here to say this is very important in technical diving where mixed gases or higher pressures are involved.
If you do opt for the DIN valve, what happens when you decide to take a trip in the Caribbean on a charter boat that has nothing but Yoke tanks on board? Enter the adaptor for allowing your DIN regulator to adapt to the Yoke valve.
OK, now that we have solved that problem, what does the diver that has purchased a DIN regulator tank but their buddy wants to borrow the tank to use with his yoke regulator. The industry has also provided for that with an insert for the DIN tank valve so it will accept a yoke regulator.
So, what tank and or regulator is best for you? A lot depends on what level you plan to progress to in the sport. If you're just getting into diving and plan on mainly local diving or traveling to some exotic island once a year, I would seriously consider beginning with the yoke type regular and tank, but if you are looking to make diving a major hobby where you see more technical diving in your future along with using mixed gasses, then you may want to look into DIN tanks and a DIN regulator.
How many tanks should you have? As I had mentioned earlier, when I came to Florida, I not only had my steel 72s but had purchased a couple more aluminum tanks either new or used. Then reality set in that there were not two of the four tanks that had their inspection markings alike. When one had to be pressure tested another was due for visual inspections so I had to constantly be checking to see just what dates needed attention before going on a dive.
How did I solve this, I sold them all! Since moving to Florida, I entered a realm of rental, which we did not have a lot of in Ohio. I soon learned that whenever I went on a charter off shore I would just pay the cost to rent a couple of tanks thereby saving myself having to deal with the cost of the inspections as well as not having to transport my tanks to the location as well as carry them out to the boat and back. In addition, if you are planning on traveling to an island or live aboard, the tanks and weights are included in the price so you don't need them for that either.
Finally, if you want to travel to a local lake, springs or quarry just go into your local dive shop and rent tanks for the day or weekend and bring them back. No Purchase, storage or inspections just take it back and it's out of mind.
There are a lot more details you can look into about scuba tanks that will make your head spin. You can get into the way the tanks are manufactured, how they are coated on the inside as well as outside, who makes them and where are they made, etc. When you come down to it, all tank manufacturers have to adhere to US DOT standards, much like the DIN operation in Germany.
Just be sure you are visiting a reputable dive shop and if they're quick to condemn your tank because it didn't pass some inspection of theirs, take it to another shop for a second opinion before jumping to purchase a new tank.
You can purchase tanks new from a dive shop, Amazon or a number of on-line scuba retail shops. If you are going to buy used be very careful and if you can, have a dive shop do an inspection of it prior to purchase. I did touch on this in one of my previous blogs "Checking Out Your Scuba Gear".
I sincerely hope I have shed some light on my experience in handling tanks both personally and the 10 years I worked at a local dive shop in Florida.
At this time I wish to invite all my readers, if you have an area of diving you would like me to comment on and/or share my experience with in one of my next blogs, please don't hesitate to contact me at my email address scubageorge2@gmail.com with your suggestions.
George