How to Determine the Volume of a SCUBA Tank

The amount of air, or volume, in a SCUBA tank is important in dive planning because it directly impacts the amount of time you can dive at a particular depth. The volume of a SCUBA tank is a measure, typically in cubic feet but also sometimes in liters, of how much air the tank can hold at a given pressure. For example, an 80 cubic foot tank with a fill pressure of 3,000 psi will contain 13 cubic feet of air when the pressure in the tank is 3,000 psi.
SCUBA tank manufacturers permanently stamp markings into the exterior of a tank so they are in compliance with United States Department of Transportation regulations. Manufacturers typically include volume as one of these markings.

Instructions

Difficulty: Moderately Easy

Things You’ll Need:

SCUBA tank Manufacturer's specification
SCUBA tank
Manufacturer's specification

Step 1

Look on the neck of the SCUBA tank to find the stamped manufacturer's name.

Step 2

Look up the manufacturer's specifications for a description of the neck markings. Neck markings are sometimes called crown markings.

Step 3

Look on the neck of the SCUBA tank for the volume marking, using the manufacturer's description as a guide to which marking to read. This marking is typically something like AL80 or S80, which would indicate aluminum-80 or SCUBA 80.

Step 4

Read the number of that marking as the volume of the SCUBA tank, which is read as either cubic feet or liters depending on the manufacturer. For example, Catalina Cylinders uses a cylinder identifier of S80 to indicate a SCUBA tank with a volume of 80 cubic feet.

Tips & Warnings

The South Florida Spearfishing Club has a tank volume calculator on their website. This tank calculator computes the volume of gas actually in the tank based on the tank's volume rating, psi rating, and actual psi.

Although the U.S. Department of Transportation does not require volume to be stamped on the exterior of a tank, reputable manufacturers include it in their standard stamp. If you have a tank that does not include these permanent stamps, fully investigate the safety of the tank before using it.

Resources

Article Written By Susan Roberts

Susan Roberts has more than 15 years of marketing, business and technical writing experience. Her business writing has appeared in online trade publications such as TechWeb and ComputerWorld. In 2009 she began publishing online articles in categories including healthy living, family and food and wine. Roberts has a Bachelor of Arts in technical writing/mass communication from Texas Tech University.

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