Scuba Tech Tips: How Much Air? Cubic Feet or Liter's – S06E18

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Still on vacation in South Africa, the dive shop asked what size tank he wanted, 12 litre or 15 litre? Alec explains air fill differences between North America’s cubic feet of air in the tank vs tank volume in liters.

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20 Comments
  1. Random 13 says

    Looks like Blue Ocean Dive Centre in Umkomaas, loads of black tips up top and raggies on the Aliwal reef….hope you got lucky and saw a tiger Alec!

  2. caetano coutinho says

    I have problems with ears while diving .most of the times water goes wts solution.any solution for protection for ear drum

  3. caetano coutinho says

    How Long last 12 liter in 15 meter dept average person in ocean .alec thanks.is it good idea to two tank for spear fishing?.thanks for giving us valuable time .I am learning scuba diving

  4. ScubaTastic says

    I have a question; how long can air in a tank be stored away without getting bad? Some people say few months other say 2 years with 50Bar store pressure other say put away with full pressure.

  5. Pricediver says

    These videos are so fun and helpful !! I can literally learn new stuff in every single tech tip videos. Thank you Alec

  6. darreng34 says

    We fill tanks to 200 bar in europe (plus minus). Not 232. Very easy. When you get to 100 bar, turn around and shallow up. Nothing could be easier. Safety stop at 50 bar. Minimum exit pressure 30 bar.
    Din are much safer than yokes. I like to provide the o ring rather than rely on a rental yoke o ring. Also din can handle higher pressures.

    12l at 100 bar relates to 1200l of air. What could be easier?

    On dive boats I often hear hissing coming from yoke divers. They're then stressing trying to sort the problem before jumping in. The Din divers watch the chaos with amusement.

    Never understood this psi business and I'm British (we invented the imperial measurement system)! Yes we're also metric!

    Being different makes the world a great place. Thanks Alex for the awesome videos. Keep up the great work.

  7. Skunki says

    We are able to buy imperial tanks in Europe. Cave divers and Tech divers use 80 cft as stage tanks for oxygen and decompression gases. They are stamped as 11,1 L. Imperial tanks are constructed somewhat different. When I empty an original metric 10 L tank, they will still drang you down. When you empty an 80 cft tank and lose it, you'll send it to the birds.

  8. MDO VIDEO says

    Can you rent a 100cf aluminum tank

  9. MDO VIDEO says

    What is the biggest size tank you have seen

  10. Oli4Post says

    First, I enjoy your video's! Keep it up! But I disagree with the conclusions Cubic Feet as OP is a better measure than the size of a tank. I understand your point of view but you miss the essential part we in Europe always look at/teach the size combined with the pressure. You don't get the max pressure of OP in you tank after fill and therefore you don't have the "cubic feed" OP equivalent available. Normally after fill the tank is still hot and when it cools down the pressure will drop to 190 or 200 bar. So, the amount of available air is always the result of a fixed value (size of the tank) and a variable (pressure). So when I want to go into the water and check my available air, I look at my pressure gauge and when it says 200 I instantly know with a 12 liter I have 2400 liters of air. How hard is that!?! When it is 180 bar it is 180×12 = 2160 liters. Still easy. And when I have a 10 liter the number of available air is 10×180=1800 liter or 10×232=2320 liter. Now, if my only information is that I have a 2784 liter tank (12 liter on 232 bar) like the Cubic Feet indication, I really have difficulty to recalculate (by head) the available air if my pressure gauge indicates I have 190 bar. It is 190/232*2784. I teach my students how to make a dive plan for every dive (on all levels). I prefer a simple and calculation bast on actual pressure. Size of tank x actual pressure = available air. Though with non-technical simple dives we turn around at 100 bar (1/2 tank) and surface at 50 (1/4), a lower tank pressure still means an adaptation of the dive plan based on less available air.

  11. Joe Soap says

    In Europe we use litres because that tells us the volume of the tank, ie how much space is inside. (We use litre for everything else too, like buying alcohol or Coca Cola, because 1 litre of water = 1 kg, handy if you need to measure & only have a weighting scales since lots of stuff is water based & similar density). So litres are more natural to use.

    For the pressure we use Bar because 1 bar = atmospheric pressure. That’s also very natural & easy to get a grasp of. Especially when we go underwater because for every 10 metres of depth the pressure goes up by 1 bar. ( at 10metres depth, the pressure is 2 atmospheres so the air volumes are halved, 20 meters there’s 3bar around you, air volumes are a third of normal. Easy to do on the fly!).

    It also means that at working pressure 232 bar (232 atm), we have 232 x 12 litres of air to breathe. Not too hard on the brain. Try working these numbers out using psi & cubic feet, you’d need a calculator to get the same accuracy

  12. Nick says

    Have you seen the new Garmin descent mk1? do you have any thought?

  13. John McGuinness says

    great vid as always mate, but where is Desiree ?

  14. amir khan says

    Hello Alec, I’m having dry mouth problem while diving and it’s quite painful. Is it because of my regulator 2nd stage ? Kindly help me as it’s really a stopper for me

  15. AbyssWalker says

    The way those tanks are is the exact same as we have in Australia, but we use mostly yoke valves.

  16. Not the ATF says

    I'm 15 and I've taken my confined dives and then I'll do my open water dives this spring for my certification, my step father is a master diver and my mom is also getting certified this spring. My joy for the water is from lake Ontario over in water town close to where your from. Your antique scuba series is awesome btw

  17. owen mougenot says

    Hi Alec, Another area for confusion is with the regulators. If the area uses bar in stead of psi the dive master might be confused with the readings on a non local unit. This happened to me in Cuba recently since I brought my own reg (psi) on a dive and they ran me down to 100 psi, I was under the pickup boat doing the safety stop so not a big concern but I don't like being that close to empty. Hope to see videos of the shark dives you are going on. Thanks Owen m

  18. Andrew Starmer says

    Great video Alec as ever, what about one on full faced masks as they become more used by recreational divers

  19. Alain Dumesny says

    interesting that our US steel tanks (many of which are made in Italy by faber now that worthingtons (which I have) and PST are no longer made) are 3442/3500psi so 237/241 bar slightly higher than 232 you mentioned. Likely all the same tank, but stamped differently for different regulations/markets.

  20. troop1026 says

    What is there to say my friend another great video.

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