Can You Change Scuba Tanks Underwater?

Last Updated: November 30, 2023

Yes, you can change scuba tanks underwater. The process is called a gas switch or gas swap. It is a relatively simple procedure that can be done in a few seconds, provided you have the right equipment and are well-practiced.

Some people call it a tank switch, but this term is less accurate as many other things besides the scuba tank itself go into the equation. Switching air tanks underwater is a critical safety skill, and any diver should know how to do it in case of an emergency. This can help you get more bottom time or deal with an out-of-air situation for one of your buddies.

diving with multiple tanks

Switching Air Tanks Underwater

Before going into details, it’s important to understand that you must be trained to change air tanks safely. You should never attempt this without proper training. When you want to change your oxygen tank, you first need to know what kind of tank valve you have. They come in three different configurations: manifolded, twinned, and independent.

The configuration is a big deal when it comes to swapping a scuba tank underwater because each one will determine whether or not it’s safe for you to switch out your air supply.

Are Scuba Tanks Refillable?

Yes, scuba tanks are refillable. However, it’s not as simple as filling up your car at the local petrol station!

Scuba tanks are filled with compressed air, which means that the air inside the tank has been squeezed into a much smaller volume. This takes special equipment to do correctly and safely, so you’ll need to take your tank to a dive shop or fill station to get it refilled.

How Many Times Can You Refill a Scuba Tank?

Scuba tanks are made from steel and aluminum alloys, and these metals will slowly corrode over time. Because of this, there’s a limit on how many times they can be refilled before they need to be retired.

So it basically depends on how old your tank is. The older the cylinder, the more exposed it is to the elements, and the more likely it is to fail an inspection. Some people like to compare tanks to cars, saying that they will always eventually break down no matter what you do.

This number varies depending on the size of the tank, but as an example, an 80 cubic foot steel tank should be disposed after 300 fills.

The average life expectancy of a scuba tank can vary depending on where it was made and how much it has been used. If you are someone who fills your tank up every day or two, then you should probably plan on replacing it after 5-10 years of use. If you only use your tank a few times per year, you should be able to get 15-20 years out of it before needing a replacement.

Can You Dive With 2 Tanks?

Yes, you can dive with two tanks. The only thing you need to do is make sure that the first tank you will use is the one you have your primary regulator on.

This is because when you breathe off of a tank, you will always be putting more pressure on your regulator. So, if you were to breathe off of your second regulator on your second tank, the gas would not come out because it would be fighting against the pressure of the first tank.

If you want to dive with two tanks and use one at a time, all you need to do is hook up your octopus (secondary) from the second tank onto your BCD. Then, when there is no air left in the first tank, simply switch over to your octopus and continue diving with your second tank. It’s really as simple as that.

Final Thoughts

Ultimately, there are many variables to consider before deeming oxygen tank changes difficult. The size and complexity of the tank(s), buoyancy control placement, and the presence (or lack) of a dive boat on standby all come into play when deciding whether it’s practical to make an oxygen tank change during a dive.

While it seems that most recreational divers would not be able to do this without endangering themselves or others, trained professionals can perform these tasks without hesitation, under the right circumstances of course.

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