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  • Writer's pictureBrian

Gear Assembly & Pre-Dive Checks – Tiny Metal Bombs

Hello everyone, today we are providing a quick refresh on how to assemble your gear and why it is important to check your equipment before going out on a dive. This will be a multi-part series working our way from the tank to the BC, looking at the weight systems, and finally the regulator.


If it’s been a while since you’ve put your gear together or you are used dive masters and instructors putting your gear together then listen closely. It doesn’t matter if you are a new diver or an experienced diver, every diver should know how their equipment works and how to trouble shoot it.


Valve Faces:

So, let’s start with the simplest one – your tanks…or cylinder, or bottles, or whatever else you like to call the pressurized metal bomb strapped to your back 😜 


The first thing I like to check is the O-ring (if it’s for a yoke). Look and see if the O-ring:

A) is there

B) what condition it looks to be in


If the O-ring looks worn out or has little scratches and cuts in it, then this could be an indication of a potential failure in the water. Last thing you want is to hear a loud pop behind you followed by hiss of air escaping from between your regulator and the tank.


While you are looking at the O-ring take a minute to inspect the valve face. Does it have threads? If it does, then most likely you have a DIN valve which is designed for a DIN regulator to thread into. Do not be alarmed. There is not supposed to be an O-ring here.



Air Check:

Next, I like to sample my air before hooking up my regulator. Remember, high quality air should have a refined dry taste in your mouth, leaving you thirsty at the end of your dive 😂 AKA cotton mouth.


To test the air place your hand over the valve and carefully open the valve until some air blows out over your hand. What we are looking for is dry odorless air. Anything else like oil, water, dust (brown or white), or any funny smells means you should not use that tank.


Oil and water can mean the filters on the air compressor are old or expired and should be replaced. Water can also be a sign of moisture inside the tank from a “Wet Fill”; when water is blown back into the tank during the re-fill process. Red dust can be a sign of excessive rust from a steel tank and white dust can be a sign of excessive oxidation in an aluminium tank. Yes, I spell it AL-U-MIN-EE-UM.


Cylinder Markings:

If everything has passed so far, then it’s time to move onto the more technical aspects of your tank. The tank markings. While it’s a good idea to familiarize yourself with what all the markings mean the ones we are focusing on today are the material, the tank pressure, size of the tank, and the most recent hydrostatic test date.

Remember tanks can be made of steel or aluminium and different sizes and pressure ratings can affect your buoyancy. Now chances are you will most likely find aluminium 3AL (3ALM), 80cft (11 litre), 3000 PSI (310 BAR) on most tanks you rent when on vacation, but that doesn’t mean that will always be the case.

Especially if you are a gas guzzler or are more of a floater than your buddies, you may want a high-pressure steel. Most aluminium tanks start to gain positive buoyancy when you are more than halfway through your air. Now that’s not a big deal when your deeper than 30 ft (10 metres), but as you get ready for your safety stop you may find it more difficult to maintain neutral buoyancy.


Steel tanks will retain their negative buoyancy qualities even as the tank pressure decreases, which means it is easier to maintain neutral buoyancy at your safety stop and you won’t need as much weight as someone in an aluminium tank. Also, steel tanks are available in 100cft (12.9 litres) giving you a larger volume of air to use on your dive.


It’s always prudent to do a weight check with your dive leader if you don’t remember what you use. And don’t worry about how much weight you use, everyone is different. I’ve seen 6’4 250lb man use 2# in a 5mm wetsuit and 5’3 120# woman use 20# in a 3mm. Some people float and some people sink. I am a sinker, but personally I wish I could just float and not have to kick to always stay up.




Last thing we are going to check is the hydrostatic test date. This is stamped into the neck of the tank near the valve. They are stamped with the month first in big numbers, followed by a funny symbol or 4 smaller letters and numbers in 2 columns and rows, and then lastly the year.


Tanks are required to be tested every 5 years in which the tank is over pressurized to 5/3 of its working pressure. During this process the tank is submerged in a sealed chamber and the inspector looks for changes in the volume of the tank or any other noticeable differences. After the hydrostatic test the tank is visually inspected externally and internally for any damage.


If the tank should fail any of these tests or inspections, then the tank is condemned and pulled out of service. If you find a tank without a visual inspection, not the worst thing in the world. Who knows it could have come off during a dive or it’s on the bottom of the tank where we don’t always think to look. However, if your tank is missing that 5 year stamp, meaning it’s been more than 5 years since it was last tested, then DO NOT USE THAT TANK.


This is part 1 of our series. Next article will focus on the BCD and the assembly and testing process when setting up your gear.


As always, this Brian (owner of Bamboo Reef) your fearless leader. I’m always lost, but happy to share the journey with you.

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