SCUBA Tank (Cylinders) FAQ

Products - Gas - Cylinders

Because there are so many choices, even experienced divers can become confused by the latest features and diving applications of scuba tanks. If that's you, then you might benefit from reading the most popular article on our website. How to Select a SCUBA Tank is a very detailed whitepaper focused on helping divers choose the best SCUBA tank for their specific needs and styles of diving.

The bottom line is that all SCUBA tanks will have cosmetic imperfections from the factory and recently their cosmetic quality has noticeably declined. The recreational dive industry has long been accustomed to a "consumer grade" finish on SCUBA cylinders. However, recent changes in the marketplace means new SCUBA cylinders may often present with what could be charitably described as an "industrial grade" internal and/or external surface appearance that is similar to what is typical of bulk supply cylinders. The surfaces can have streaks of discoloration, spotting, oxidation, and other minor irregularities as a byproduct of manufacturing, testing and handling.

Currently, all the cylinder manufacturers are adamant in maintaining the position that their SCUBA cylinders are O2 clean and fit for purpose as delivered from the factory. This puts the distributors and retailers of SCUBA cylinders between a "between a rock and a hard place" when consumers or untrained "inspectors" object to the appearance. If the distributor or retailer does any modifications (such as further cleaning, tumbling or grinding) to the brand new cylinder warranted as O2 clean and fit for purpose from the manufacturer, then legal responsibility for the condition of the cylinder shifts to the aftermarket service provider. A cylinder with aftermarket treatments also technically can no longer be represented as new and O2 clean from the factory. Most retailers choose to follow the experts in this circumstance - the manufacturer plus the independent testing agency plus the certified cylinder visual inspector that all warrant a brand new and unused cylinder is fit for purpose.

With just minimal care, all tanks regardless of their cosmetics will deliver many years of service. We occasionally encounter consumers who seem prioritize the cosmetic appearance of their tanks over more significant considerations. Our practice regarding new cylinders the customer deems cosmetically unacceptable is we will accept returns (according to our Returns & Refunds policy) but will not make exchanges given the likelihood a replacement will be no better cosmetically than the original. Since the shipping on cylinders is not free, our advice to those consumers is they should reconsider their priorities. Otherwise, if cosmetics is important to ownership, they might prefer renting tanks rather than owning or purchasing locally where they may personally inspect before purchase.

As of Summer 2022, the Metal Impact brand name is being transitioned to the Thunderbird brand of their parent corporation, Thunderbird Cylinders (which also acquired Luxfer brand aluminum SCUBA cylinder assets), but the cylinders are otherwise unchanged. The exclusive North American distributor for Thunderbird SCUBA cylinders is now XS Scuba. During the transition you may find references to any of these names on our website, but they are all referencing what are essentially the same aluminum SCUBA cylinder products.

We strongly recommend purchasing our cylinders ONLY for use in North America and the Caribbean. All our cylinders have United States DOT and Canadian CTC testing and crown markings along with Imperial neck thread forms. The cylinders are NOT marked appropriately for use in Australia and New Zealand. Testing and marking specifications, neck thread forms, and over pressure relief device requirements in many other areas of the globe (especially Europe) are different than North American standards.

In the US and Canada, SCUBA Tanks must be hydrostatically tested every five years (60 months) and we always ship cylinders with the absolute most current test date available to us. Most cylinders have a factory test date less than 12 months old. Less popular sizes of cylinders may have a slightly older factory test date as these are manufactured infrequently.

No, due to weight restrictions our doubles packages ship as individual components ready-to-assemble: two cartons containing the cylinders (and boots for those packages that include boots) with modular valves (including port plugs) installed in the cylinders hand tight along with a third carton containing the manifold crossbar, bands and bolt kit, two loose Evidence of Inspection decals (aka VIP stickers.). You will need to assemble the package yourself prior to filling or if you prefer arrange for a local dive shop to assemble them for a fee. Assembling a set of doubles is easy if you follow our detailed doubles assembly instructions.

Yes, they will be assembled and ready to fill, if shipped via ground service within the continental United States. Transportation security and customs regulations require cylinders that ship via air transport to be obviously empty and easily inspected. Effectively that means the cylinder and valve cannot be assembled if shipping to an international address (including Canada) or via any expedited shipping method.

If you are arranging to have your cylinders delivered to a third-party package forwarder for subsequent handling, you may wish to request on your order that we do NOT assemble your cylinders and valves.

All cylinders and valves sold by us, that we describe as Nitrox Ready, are oxygen clean and oxygen compatible from the supplier. Based on oxygen handing best practices, Dive Gear Express does not use any form of lubricant during valve installation. That means all Nitrox Ready SCUBA tanks sold and assembled by Dive Gear Express, prior to initial use, are oxygen clean and oxygen compatible from the supplier; we have done nothing to change that condition.

In rare cases, a shop will insist on some form of after-market "cleaning" before agreeing to fill a tank not sold by them. They have that right, but we want you to know that no such service can make a new empty cylinder and valve from Dive Gear Express any more oxygen clean or more oxygen compatible.

Every tank we sell is inspected by us immediately prior to shipment and all our technicians are PSI-PCI certified to perform such inspections. If the cylinder is ordered with valve and VIP, we include our shop evidence of inspection 3" X 6" month and year dated decal (aka "VIP sticker") that clearly indicates "Nitrox Ready" in large yellow letters on a green background. However, If the cylinder is ordered with the "No Valve / No VIP" option then our evidence of inspection decal is not included even though the cylinder itself is always inspected.

No, our tanks don't include the Large Nitrox Tank Wrap Decal used to indicate gas contents. If the cylinder is ordered with valve and VIP, we include our shop evidence of inspection month and year dated decal (aka "VIP sticker") that clearly indicates "Nitrox Ready". However, the VIP sticker is not used to indicate the gas contents and Nitrox Ready does not mean there is actually Nitrox gas in the tank. The tank wrap can be ordered separately, however please read our TekTip titled Do I really need that big NITROX wrap decal on my tank?
The CCR Cylinders and Valves in our Rebreather category have differences in their configuration than those in our Gas-Tanks category. The cylinders and valves themselves are physically the same in both categories; equally oxygen compatible and oxygen clean. However, the CCR cylinder selections are only appropriate for rebreather in-board mounting and include options to add Oxygen/Diluent contents decals. Cylinders configured for CCR will ship with the VIP decal unaffixed so it can be later applied to the cylinder wall in a location unobstructed by rebreather tank mounting systems. The CCR valve configuration options include our specialized versions typically only seen on rebreathers, along with options to select knob color and do not include a No Valve/No VIP option. Rebreathers only use DIN regulator fittings, so the included valve accessories for CCR are a threaded dust plug rather than a vinyl cap and do not include a DIN-to-Yoke insert adapter.
Yes you can, but we don't recommend it for two reasons. We buy the cylinders with a valve at a discounted bundle price and we pass that discount on to you. If you wish to purchase the cylinder without the valve then the reduction in price we can offer is a meager $30.00 considering the price of the valve and a VIP when sold separately. While we always inspect the cylinder before shipping, if there is no valve then we can't provide a VIP decal because it only applies to both the cylinder and valve together. It only makes sense to purchase without valve when you have absolutely no use for the valve and don't need the VIP decal.
The "Rejection Elastic Expansion" (REE) number stamped on the crown of some steel SCUBA cylinders is the maximum volume in cubic centimeters the manufacturer specifies the cylinder may expand during a hydrostatic pressure test. It is guidance to the tester and of no significant concern to divers. The REE number, if present, is NOT the free air capacity of the cylinder.

Yes, but it's meaning is often misunderstood. Our low pressure steel cylinders are DOT-3AA-2400 design i.e. their fill pressure is considered to be 2400 psi by the US Department of Transportation rules. When we talk about LP cylinders having a 2640 service pressure, that is always 2400 + 10% overfill = 2400 + 240 = 2640 psi. It does NOT mean a 10% overfill on the 2640 psi service pressure.

If 3AA design cylinders can pass a elastic expansion evaluation during hydro testing then they qualify for a "+" stamped next to the hydro date. That "+" means they may receive a 10% overfill. This overfill allowance was instituted to improve material capacity during war time almost a century ago, but the rule remains in effect today. New cylinders will always pass, but although rare do fail on later tests, especially those that have been consistently overfilled. Many hydro test facilities will not stamp the "+" on subsequent tests after the first, because frankly the DOT prefers the + not be used.

Hot-dip galvanized (HDG) tanks develop a streaked and mottled appearance although over time that becomes more uniform. Do NOT attempt to remove the white, grey, or black looking discoloration, it is normal and part of the protection provided by the zinc metal coating.

Hot-dip galvanizing (HDG) on Faber brand steel tanks offers the best possible durability and corrosion protection. However, the cosmetic appearance of the thick hot-dipped galvanized finish is NOT as perfect and consistent as a painted finish over hot-spray galvanizing. We feel cosmetics is unimportant in relation to durability and only offer HDG finish when available for steel tanks.

No, but don't worry - we will completely seal your cylinder so that it will arrive with a factory oxygen clean interior. We sometimes receive this question based on the mistaken belief that filling the cylinder is necessary to protect the interior from contamination or moisture, however the US Department of Transportation says any SCUBA tank containing compressed gas can not legally be shipped via ordinary parcel delivery services.

If the tank was assembled by Dive Gear Express with our Nitrox Ready evidence of inspection decal (aka "VIP sticker"), then your oxygen clean and oxygen compatible tank is ready to fill without further preparation. Although local dive shop fill policies vary, there should be no safety related reason for objecting to initially filling the empty SCUBA tank with oxygen compatible grade Air or Nitrox. However, shops often enforce training agency requirements or community practices for labeling, which may require additional specific gas contents or MOD decals be affixed to the tank.

YES, you can take empty SCUBA tanks on airplanes. However, the Transportation Security Administration (TSA) has some very specific inspection conditions for tanks to be permitted in aircraft. For details, please see our TekTip Advice for Flying with SCUBA tanks.

Dive shops following best practices will not fill cylinders marked as being oxygen clean with ordinary CGA grade "E" compressed gases typical of most dive shop fill stations. In this case, the fill station operator can simply remove our Nitrox Ready decal and replace it with one they prefer. If you wish to order any of our tanks intending to use them strictly for air only, then upon request we can substitute an "Air Only" black and white version of our shop evidence of inspection decal (aka "VIP Sticker").

Quick Reference for 232 bar cylinders:
18L (141 ft3) and 15L (117 ft3) = 8-inch (large);
12L (95 ft3), and 10L (78 ft3) = 7-inch (standard);
7L (54 ft3) and 5L (39 ft3) = 5-inch (small).

These are simple approximations, for more detailed explanations please read our article Metric vs Imperial SCUBA Cylinder Sizes.