Litres, metres and bar

Diving with the metric system in Australia

American divers diving in Australia can become somewhat confused because we use the metric system. Instead of measuring depth in feet, we measure it in metres. Pressure is measured in bar, weight is measured in kilograms, and tank size (we call them cylinders) is measured in litres.

Of course we can't forget temperature. As far as Victorian divers are concerned, water temperature in the summer gets above 21 degrees the way we measure it. Burrr that's cold, isn't it?

Imagine a group of American divers exchanging confused looks at the beginning of their first Australian dive briefing. Their dive master says, "We'll descend to 30 metres, explore the wreck until we reach 80 bar, and return to the boat after a three minute safety stop at five metres. Don't forget to take a few kilograms off your weight belt since we won't be using wet suits, after all the water is a nice warm 21 degrees."

If you were one of those being briefed, would you be confused? One of the most important things you learned while getting certified was not to panic. Don't do it now either. This stuff isn't that hard, even if you flunked high school math. After reading this article you'll be able to work through it.

Let's take a look at each of these goofy measurements without going into all the decimal points and other boring stuff. By leaving out the math, you won't get bored. If you're a tech diver and want to know how to figure things out down to the last square cubed decimal power to the Y factor, you're reading the wrong web page.

Litres

Take a look in your refrigerator at that large plastic bottle of soda. The label says it holds 68 US fluid ounces, or 2 litres. If it were a scuba tank, you'd be looking at a 2 litre scuba tank, which would be about the size of a very, very small pony bottle. Not very confusing huh?

Unless you're a tech-diver, you're used to diving aluminium 80s. You probably have a few in your hall closet with out of date VIP stickers on them. The Australian equivalents (as far as capacity in a basic sense is concerned) to your beloved 80s, are 10.5 litre tanks. Of course the 10.5 litre Australian tanks are typically made of steel, so they are heavier than aluminium tanks, even though they are shorter than 80s.

If you're a tech diver with a set of double 100s, you can store 12 litres of coffee in each tank for those late night Flipper or Sea Hunt reruns.

The bottom line about tank size is this: in Australian diving standards, scuba tanks are measured by the volume of water they can hold in litres.

As a better guide, the following table gives you the dimensions and properties of a typical range of steel tanks, as used in Australia. These tanks all have a rated fill pressure of 232 bar (3,365 pounds per square inch) and a tested pressure of 348 bar (5,047 pounds per square inch).
 

TANK DETAILS
  Water
Cap.
Tare
Weight
Len. Dia. Buoyancy
Empty Full
25 cf 3 litres
101 US fl oz
3.4 kg
7.5 lbs
500 mm
19.7 in
100 mm
3.9 in
-0.5 kg
-1.1 lbs
-1.25 kg
-2.8 lbs
40 cf 5 litres
169 US fl oz
5.8 kg
12.8 lbs
460 mm
18.1 in
140 mm
5.5 in
-0.5 kg
-1.1 lbs
-2.0 kg
-4.4 lbs
55 cf 7 litres
237 US fl oz
7.6 kg
16.8 lbs
605 mm
23.8 in
140 mm
5.5 in
-1.0 kg
-2.2 lbs
-3.0 kg
-6.6 lbs
75 cf 9 litres
304 US fl oz
10.4 kg
22.9 lbs
495 mm
19.5 in
178 mm
7 in
-1.5 kg
-3.3 lbs
-4.0 kg
-8.8 lbs
85 cf 10.5 litres
355 US fl oz
11.3 kg
24.9 lbs
560 mm
22 in
178 mm
7 in
-1.0 kg
-2.2 lbs
-4.0 kg
-8.8 lbs
100 cf
standard
12.2 litres
413 US fl oz
12.9 kg
28.4 lbs
625 mm
24.6 in
178 mm
7 in
-0.75 kg
-1.7 lbs
-4.25 kg
-9.4 lbs
100 cf
compact
12.2 litres
413 US fl oz
14.2 kg
31.3 lbs
515 mm
20.3 in
204 mm
8 in
-1.5 kg
-3.3 lbs
-5.0 kg
-11 lbs
125 cf 15 litres
507 US fl oz
16.5 kg
36.4 lbs
610 mm
24 in
204 mm
8 in
-1.0 kg
-2.2 lbs
-5.25 kg
-11.6 lbs
150 cf 18 litres
609 US fl oz
22.4 kg
49.4 lbs
715 mm
28.1 in
204 mm
8 in
-0.75 kg
-1.7 lbs
-5.75 kg
-12.7 lbs

Metres

A metre is 3.28 feet. Why? Well that's another story. For now, just accept it is.

Why should you care? Depth descriptions of dive sites given during dive briefings in Australia, are given in metres. If you are renting gear, your rented depth gauge or dive computer will tell you that you're at 18 metres instead of 60 feet deep.

Unless you have a waterproof calculator, you may want to write a metre to feet conversion table on the back of your slate. After all, you'll need something to do on the bus trip out to look at those kangaroos in the bush, just in case you decide to spend the day not diving. Or you can use this one.
 

DEPTH  
Metres Feet Used for...
3 metres 10 feet Safety Stop
5 metres 15 feet Safety Stop
18 metres 60 feet Open Water depth limit
30 metres 100 feet Advanced Open Water depth limit
40 metres 130 feet Recreational Diving depth limit

Bar

Bar is the way Australians measure pressure, as well as a place we go when the weather is too bad to go diving.

If you want to get technical about it, (without wearing doubles that is) 1 bar equals 14.5 psi. So if you take a 10.5 litre tank and fill it to 232 bar, you'll have about 85 cubic feet of air at 3365 psi. Almost like an 80. Get it?

Most Australian dive operators will insist that you are back on board the boat with at least 50 bar (725 pounds per square inch) in your tank. Luckily for you, most Australian pressure gauges have the red warning block between zero and 50 bar, and we all know why.

Weight a Minute

Did you know that a 15 kilogram weight belt will send you to the bottom faster than one weighing 20 pounds? You should, because when the nice Australian dive master asks you how much weight you'll need when picking out a rental weight belt, you could become an anchor instead of a diver if you don't.

A kilogram is 2.2 pounds. A good rule here is to divide what you wear back home in half. That's how many kilograms you'll need, as long as you're wearing the same thickness of wet suit you normally dive.

Where's the Ice?

"The dive master says the water is 26 degrees, shouldn't I rent a dry suit?"

No, not at all. That was 26 degrees Celsius. The water is really 80 degrees Fahrenheit. Temperature conversion requires a calculator unless of course you're a math wiz. To save time and brainpower, take a peek at the conversation table below. It covers most temperature ranges for recreational diving.
 

TEMPERATURE
Fahrenheit °F Celsius °C
40 °F 4.4 °C
50 °F 10 °C
60 °F 15.5 °C
70 °F 21 °C
80 °F 26 °C

So What Else is Different?

Remember those short scuba tanks? They're not only different because they're short. Put a DIN valve on top of the tank, and watch the American diver try to figure out how to attach his or her regulator.

Actually, it not so bad. Unlike the Europeans, most Australian dive operators use Yoke valves, just the same as most American dive operators. The Australian dive operators that use DIN valves usually have it as an option, not as their standard. So if you're bringing along your own DIN regs, it would pay to be safe and bring along your regulator DIN to Yoke adapter as well.

We talked about the temperature in the last section. Many Victorian dive spots require thick (5 mm or 7 mm) wet suits and hoods Not something many "tropical resort divers" are accustomed to.

The quality of hire gear will be as good, or better, than you're used to. However, you may save a dive or two by calling ahead and asking what brands and equipment configuration a dive operation uses as rental gear.

When in Rome?

You know the saying, and it's true when it comes to diving too. While you're on the phone to a dive operator asking about their equipment, ask about their dive procedures as well. Make sure the methods used, and sites visited, are within your skill level.

Do not be afraid to ask for help or further explanation of a procedure from a dive master or instructor, and don't be afraid to cancel a dive if you're not sure it's for you. Shop around until you find a dive operation running dives that are right for you. If you have a buddy, talk it over with him or her. If one of you doesn't want to go, don't go.

Speaking of Your Buddy?

If you left your dog and favourite dive buddy at home to take care of the house, you'll obviously be paired up with someone you've never dived with before, unless one of those really neat coincidences occur. Thanks to the popularity of the huge US based dive certification organisations like PADI, there's a good chance you may end up diving with someone who has been trained to dive the same way you were. But you're not always that lucky.

Find out who you'll be diving with before the dive, and talk to that person about his or her skill level, and expectations for the dive. Talk about emergency procedures, and make a dive plan you both understand and agree to.

Speaking of Talking

Australian dive organisations have dive masters and instructors who speak English. Some may speak other languages as well.

Dive briefings are important, but only if you can understand what is being said. If you don't understand something, ask. If you don't agree with something, please raise your concerns.

So there you have it. Once you tame your litres, metres, and bars you'll be ready to dive anywhere.

Safety in Diving

Diving Tips

  1. If you require the services of an instructor or dive master to go with you on a dive, then ask to make sure this is included.
  2. Inspect equipment and become familiar with it (even if it means a pool or shore dive first).
  3. Review dive procedures with a dive master before signing up for a dive.
  4. Become familiar with your buddy and his or her dive skills and expectations.
  5. You've heard it before — Plan your dive, dive your plan.
  6. Inspect your rental gear before leaving the dive shop.
  7. Have fun. Make new friends (dive buddies).

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