What is a scuba tank’s lifespan? Aluminum tanks can last for 10-15 years and steel scuba tanks can last for decades; there are steel tanks made in the 50’s that are still in use today. These numbers are only achievable assuming they have been properly maintained. If not, then corrosion, rust, or physical damage can compromise a tank and force you to replace it much sooner than expected. As for how long a tank lasts in terms of using up the breathing gas, an 80 cubic feet, 3000 PSI aluminum tank can last for about 45 to 60 minutes at a depth of around 10 m (30 ft) before you need to surface.
Making sure your tank is in good condition is every certified diver’s responsibility. Since a scuba tank stores your much-needed air supply, you want to make sure it’s not compromised. In this article, we will be going over the lifespans of aluminum and steel tanks, as well as how you can prolong them. We will also discuss the safety inspections that your tanks must pass so that they can continue to be in use.
What is a scuba tank’s lifespan?
Scuba tanks are required to pass a visual inspection every year, and a hydrostatic test every 5 years in the US. Depending on where you live, certain parts of the world require more frequent hydro testing. Tests can only be done by facilities that have been approved by the US Department of Transportation (DOT).
All scuba tanks for sale should already be inspected visually and hydrostatic tested by the manufacturer, so they’re good for the initial year.
Aluminum Scuba Tank Lifespan
While we feel this estimate is too high, many dive shops say that aluminum tanks can last up to 20 years if properly maintained. We’ve seen a few aluminum tanks that have passed 3-4 hydrostatic tests. This means that they have been in use for 10-15 years.
Aluminum tanks are designed to withstand the stress of 10,000 hydrostatic tests or 100,000 refills. Technically, this means an aluminum tank should last for several decades, not just one or two. The reality is that tanks are enormously affected by the care and handling they receive. Even though aluminum tanks are most commonly used for recreational diving in tropical waters, they are still susceptible to damage.
For instance, when diving in the ocean, saltwater will lead to rust and corrosion if the tank isn’t thoroughly rinsed off. Aluminum tanks are generally more corrosion-resistant than steel, however they are not immune to it. Additionally, changes in pressure and temperature as well as physical damage can decrease a tank’s lifespan. In other words, the wear and tear of general use decreases the lifespan of an aluminum tank down to approximately 10-15 years.
Steel Scuba Tank Lifespan
Steel is a more durable material than aluminum, and theoretically they can last for up to 50 years if properly maintained. However, in the same way that aluminum tanks don’t last as long as the specs say, the reality is that imperfect care and usage causes the tank’s lifespan to decrease. It’s more accurate to say steel tanks have a much longer life span of at least a few decades, with the potential for much more if they are given exceptional care. There are tanks that have been in use since the 70s that are still going strong today.
Steel tanks require more maintenance and are more vulnerable to corrosive damage than aluminum, so one should be extremely thorough with their cleaning.
General Maintenance Tips for a Long Lifespan
If you want your tank to have a long lifespan, you need to know how to take care of it. This way, it will pass multiple safety inspections and be safe to use throughout its life. Here are some tips to keep your tank healthy and in good condition.
Always keep some pressure in the tank for storage
Having some pressure in the tank (200 psi) will keep moisture out and reduce the likelihood of internal corrosion. A full tank can increase the chance of corrosion forming inside. Additionally a full tank places immense stress on the material and can compromise its integrity if stored for longer than 3 months. Conversely, an empty tank will allow moisture to form inside.
Rinse your tank with freshwater
Salt will cause your tanks to corrode faster. After a dive, particularly in saltwater, thoroughly rinse the salt particulates off the tank before drying it and storing it. Remember to keep the tank valve closed prior to running water over it. Even when diving in freshwater, you should still thoroughly rinse it afterward.
Do not overfill your tank
Each tank has a maximum fill pressure and you should stay within it. The material will not be able to support this pressure and will weaken over time. In the worst case, the material will simply tear open which is extremely dangerous to you and everyone close by. The dive shop staff should know what they are doing, but it doesn’t hurt to let them know what your tank’s maximum fill pressure is just in case. Besides, filling up a tank costs money, so you don’t want to overpay anyways.
Handle with care
You might think that your scuba tank is a sturdy piece of equipment. It is, but you never know when a dent, scratch, or gouge will allow the metal to be corroded, weakening the cylinder. Treat your tank as gently as possible and don’t toss it around or handle it like it’s indestructible.
Store tanks vertically
Unless recommended otherwise by a visual inspector, store your tanks vertically, preferably in a tank holder so it won’t fall. If there is any moisture in the tank, when stored vertically, it will form at the bottom and corrode the thickest part of the wall tank instead of the sides.
Fill your tank at reputable air stations
If you’re getting your tank filled by a mysterious cloaked figure from out the back of his van, the air going inside probably isn’t the cleanest. Keep in mind that even small amounts of contamination, such as carbon monoxide, will be amplified under pressure. You should take measures to ensure the air you are breathing is clean. Only get your tanks filled at trusted dive shops.
Signs of corrosion
You may not be qualified to perform a visual inspection yourself, but you can still determine if your tank has been compromised. If you see or smell anything unusual out of the tank valve, it’s possible that the insides are corroded. If you tap the side of the tank and heart rattling inside, you must open it for a visual inspection.
Water inside the tank
If you find water inside the tank, and it has not yet corroded or there is very little corrosion, there is a chance to save this tank. You can rinse the inside with fresh water or steam clean it, then dry it thoroughly with warm air. Afterwards, let a qualified inspector determine the extent of the corrosion and if the tank is still in good condition or not.
Signs of problems
If you notice any possible signs of problems, you should err on the side of caution and take it to a dive shop or repair facility to have it inspected.
How to Keep Moisture Out of Your Tank
Most steel and aluminum tanks are ruined by corrosion. The best way to prevent this is to keep the tank from coming into contact outside of diving. The following tips will keep moisture away from your tank as much as possible.
Always leave some air in the tank
Do not completely drain the air out of your scuba cylinder, and if you do, never leave the valve open when storing it. If the tank is completely emptied during a dive, close the valve immediately. At the earliest opportunity, remove the valve and inspect for moisture inside the tank.
Drain air slowly
When you let air rapidly escape from the tank, it can cause condensation to form on the interior of the tank. The reason is that as the air expands rapidly, it also cools quickly, releasing some vapors in the process that will reside in the tank as moisture. If you must let air out, do it slowly. The best way to do this is to partially submerge the tank in shallow water, with the tank valve above the water, and slowly let some air out.
Only attach to dry fittings
Before attaching a regulator or filler nozzle from a compressor, check that all the fittings are dry. One way to ensure this is by temporarily opening the tank valve and then purging it before attaching a regulator or filling the tank. This action will blow away any droplets that may have formed by the opening. Even a small amount of moisture can corrode the interior of the tank over a short period of time.
Tank boot and attachments
After you rinse and dry your tank, remember to inspect the tank boot and any backpack attachments. Water may still be trapped in small areas. These accessories may transfer the water to the tank, where it may enter through nicks and scratches and begin corroding the exterior of the tank.
Safety Inspections
In addition to general maintenance, some official testing must be done on the tanks to ensure they are safe. These safety inspections verify the integrity of the tank so that you can continue to use them safely.
Once your tank passes an inspection, it will be given a sticker or a stamp with an expiration date. If your tank is expired (due for an inspection), then dive shops will not fill your tank until it has a valid sticker. Tanks that fail the inspection should be replaced as soon as possible.
The two tests that a tank must successfully pass are the visual inspection and the hydrostatic test. The visual inspection is done once a year. The hydrostatic test is done once every 5 years in the US.
The Visual Inspection
During the annual visual inspection, licensed technicians will inspect both the outside and inside of the tank. They are checking for cracks, obvious dents in the material, and corrosion. They use snake cameras and various imaging modes to inspect the interior of the tank. The valve is also inspected.
If a tank successfully passes, it receives a sticker which displays the date of the inspection and when that sticker expires. All divers should inspect this sticker to make sure that it is still valid prior to diving. When purchasing or renting a tank, a sticker that has been issued within 6 months is still considered recent.
The Hydrostatic Test
Hydrostatic tests are conducted every 5 years and require specialized equipment to test it. This test is to determine the integrity of the material and whether it can withstand the pressure of additional refills.To test this, the technicians will fill the tank to 5/3 of its maximum capacity with water. Yes, you read that right; the tank is over-pressurized to 167% of its capacity. The cylinder is held in an armored tank and submerged in water to protect the technicians in case the tank is compromised.
Both aluminum and steel will flex when subjected to this immense pressure. It is this flex that technicians will measure by calculating the displacement of water around the tank. If successful, the metal will return to its original shape once the pressure is released. If the metal remains flexed, or if the cylinder rips open during the test, then it has failed the test.
Once passed, the tank will receive a stamp on the exterior, indicating that it has passed the hydrostatic test as well as a date indicating when the stamp expires. This is so that divers can see that it still has a valid stamp before using it. When purchasing or renting, If the stamp has been issued within 2 years of a hydrostatic test, it is still considered recent.
Compromised tanks should be disposed of. However, some divers find creative ways to use the tanks as furniture or as fixtures in dive destinations.
Closing Remarks
The best way to ensure your steel or aluminum tank has a long lifespan is by taking proper care of it. Moisture is the silent killer of tanks, so you should do everything in your power to keep your tank clean and dry after diving. Follow the tips outlined above to keep your tank lasting as long as possible.
Whenever you are purchasing a renting a tank, always check for the visual inspection sticker and hydrostatic test stamp before accepting it. If you have multiple tanks, check to see that the tank you plan on diving with doesn’t have an expired sticker.
Before buying a scuba tank second-hand, ask to see a documented history of visual inspections and hydrostatic tests to ensure that the tank is still in good condition. It is your duty as a certified diver to make sure your tank is safe for use so that you do not endanger yourself or anyone around you.
That’s why if your scuba tank has failed a hydro test, then you need to dispose of it properly, just as you would as any of your other old scuba gear. If you want a scuba tank that lasts a long time, consider checking out our review of the top ones to find a reliable one for your needs.
