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

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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[@user46346bdtgry]

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

[@alaind831]

I don't think the issue is with metric (which makes so much more sense than imperial) but why measure the tank volume (which is useless without "at what pressure") as opposed to amount of air it holds - which is typically what end user cares. Same can be said about car gazoline consumption. I would much rather know how many (km,miles) I can travel with a given (L,gallon) of gaz, than how many L it takes to go 100km - I likely know the next gaz station is X km over and it's easier to know if you will make it my simple multiply (or just compare being bigger) rather than division.

[@mortenanlarsen]

Do you know the volume of the fuel tank in your car? Or would it be better to say that you have a 1000km tank?

[@alaind831]

@@mortenanlarsen of course you know the volume of your car tank because you pay dearly for it at the pump! $/gallon or euro/l. 1000km tank doesn't make sense since your consumption is such a variable from day to day, hills vs flat, traffic, etc... thought car computer will calculate that number so you know if you're gonna reach your destination which you know in distance.

[@almerindaromeira8352]

@@alaind831 but that is exactly the problem! Without a gauge I don't know the pressure inside and thus I don't know the volume of compressed air inside. 12 liters are 12 liters, that fact is invariable

[@javiercaselli]

You guys in the New World really need to start using the metric system... Just kidding, very informative as always, thanks!

[@AlecPeirceScuba_SeaHunter]

It's really only the US that doesn't use metric. Most other countries in the "New World" are metric. I'm just old and obstinate so I switch back and forth for fun. Alec

[@alaind831]

metric system makes so much more sense (having used both for a very long time), that said the US way of telling how much air you tank holds (what you really care about) makes more sense IMO. 12l tank means nothing unless you know/compare the working pressure too... in the US the typical 50/67/80/100/120 sizes really tell you how much air consumption you'll have. The pressure + material, but really the buoyancy full/empty spec, is the next number you care to figure out how much lead you need...

[@javiercaselli]

Thanks for your comment, I see your point but still, I also think that 80 cubic feet of air at sea level mean nothing the moment you get into the water, at a merely 10m/30ft dive those 80 cubic feet become 40 because of pressure, it's not a reliable figure by any means, IMHO. Bottom line is both the "European" and the "American" way of measuring the capacity of tanks only gives us starting point to work with and plan your dive. A 12l tank can last you an hour in a relatively shallow dive, and a 15l one can be drank in left than half that time beyond 20 meters. One of my greatest worries when I dive with a buddy I don't know is checking if the new guy or gal checks the gauges regularly.

[@Dive_Me_Crazy]

Shark food jumps in with shark food... I loved the way you introduced it. Imperial units always do my head in. I love getting 220 bar and sucking it till I get down to 5bar - then I stop sucking and start panicking :)

[@AlecPeirceScuba_SeaHunter]

Yeah! 5 BAR is technically empty. Time to panic! Alec

[@Dive_Me_Crazy]

The level of panic is inversely proportional to the depth. Maybe we should develop a recreational scuba panic chart?

[@pricediver]

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

[@AlecPeirceScuba_SeaHunter]

Thanks for your support Price. I hope something helps your diving. Alec

[@brianduc27]

Great video. Your the first I've seen break the difference down in an understandable way. Thanks :)

[@AlecPeirceScuba_SeaHunter]

Glad you liked it! That's what i try to do, make what others make complicated into the basic facts and how to use it. Scuba diving should be fun not work, right?

[@georgeibanez8117]

Keep making videos Alex, you have taught me so much over the years and made me a better and wiser diver!

[@AlecPeirceScuba_SeaHunter]

Thanks! Will do!

[@mvakkilainen]

Thank you for the video - Very informative

[@AlecPeirceScuba_SeaHunter]

Thanks for watching. Alec

[@bryanrhoads8058]

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

[@AlecPeirceScuba_SeaHunter]

Great to hear from you. I'm so pleased to hear that you're enjoying the best freshwater diving in the world. I've often said that divers in Ontario are the luckiest in the world. We are a 3 hour drive from the best shipwrecks in the world and a 3 hour flight from the best reefs in the world. Good luck to you and your diving family. Alec

[@amcaesar]

I’m traveling to Raja Ampat later in the year, and this is news I can use. I’m working on adapting my yoke reg to DIN in preparation.

[@AlecPeirceScuba_SeaHunter]

Glad to help out and enjoy Raja. Have been to Wakatobi and Palau, both great trips.

[@TauchEin]

I live in europe and know both systems. The truth is that in a 12l tank are a little bit more air. If I fill my 12l tank with 3000 psi there is around 85 cuft of air in it. If I fill it at 232 bar op (3360psi nobody do that) its nearly 97 cuft. If I fill to very usual 200bar (2900 psi) there are 83.5 cuft in it, while its 77.5 in the 80 cuft at the same pressure. So under all circumstances its a little bit more in 12l. Alec, thank you very much for your cool videos!!!

[@peterjulianphotos4659]

I was also thinking the same - both my 12.2 steel Faber tanks are filled to 232 which equates to 100 cuft

[@danielallis5491]

Thank you for clearing this up! I was so confused lol.

[@AlecPeirceScuba_SeaHunter]

Should have seen our divers faces when asked the same question 10, 12 or 15? Duh!!! A

[@dre64]

@@AlecPeirceScuba_SeaHunter LOL... 🙂We would have the same but the other way around... "You need 80 or 100?... Say what???"

[@theinfamousmrd]

Was hoping to be the first one to comment :(, got way too excited when I saw the notification of a new episode of Scuba Tech Tips

[@AlecPeirceScuba_SeaHunter]

Lots of good stuff coming Dalton. Thanks for watching. Alec

[@Random13]

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!

[@AlecPeirceScuba_SeaHunter]

You got it Random! And we saw lots of sharks. Alec

[@Random13]

@@AlecPeirceScuba_SeaHunter Ah glad to hear, I enjoy going to Aliwal when I can, but stay in Mosselbay in the Cape, colder water but lots of great sea mounds to explore. And our population of juvenile great whites keeps it nice and empty for us haha! ;)

[@bristol8920]

Your right about the two different systems is a minefield, we in Britain changed from cu ft to litres due to the EU rules and regulations, and if not being familiar with it you could end up buying a larger cylinder which you didn't want, and also could put you over your no stop times and into decompression territory..... So still in sth Africa lucky you ...thanks for posting and keeping in touch ..have fun and dive safe to you and your colleagues.......

[@AlecPeirceScuba_SeaHunter]

I'm used to cubic feet and that's not about to change here despite Canada being 'officially' metric. It's just too easy to use cubic feet. We're back now. Great trip. I have some Tech Tip videos about it coming and I also have some 'Alec Peirce at the Ranch' videos. Check out that other channel of mine. Alec

[@lolanakahale1665]

thank you

[@AlecPeirceScuba_SeaHunter]

Thank you for watching Lolana. Alec

[@RaynosFAA777]

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

[@AlecPeirceScuba_SeaHunter]

The debate will rage forever but the yoke has its place - cheap, easy to use, more rugged and up to 3500, perfectly safe.

[@sindrome303]

Alec I have enjoyed watching most of your videos. still got a lot to watch yet lol. Thanks for all the helpful and useful information you are putting out. I dived as a teenager with friends, but this year I payed for my 16 year old son to do his dive course, and have since done 2 beach dives with him. My first in 22 years. Diving on the South West coast of Western Australia is extremely daunting as we live in the great white capital of the world. More divers chomped here than any other part of the world. I would love to see a good video on how to act, or react in a situation with an angry shark, More so how to tell if he is hungry looking, or just generally pissed off lol. should I wave my arms around and try to look bigger, or tuck them in, so they don't get bit off. Is there any point to shooting of my spear, and if I did, would a gill shot, or a shot in his mouth make a large shark think twice. I wish I could afford a shark shield, but there like $500. these probably sound like stupid questions, I just want to know ALL my options, and maybe what to expect. are there any good shark defense's you would recommend. for someone on a budget, Sorry for the long question. Just a final, note. could you put up more footage of your dives. I would love to see

[@alaind831]

recently say a documentary on netflix: Nova "Why Sharks Attack"... don't make yourself look like a seal is probably #1 thing. Great white are very visual (see green 'gray scale' only) especially above them (attack from below, retina has more detail upper part) and the Autralia scientist were testing a wetsuit to make you blend (mix blue/green/grey), as well as black/white stripe version to make you look like a venomous snake (especially underside of surf boards). Both of which were effective. Some sharks are more sensitive to electricity so the shield worked better for them. www.netflix.com/watch/80170517?trackId=13752290&tctx=0%2C0%2Ca7d3f4a9-89be-4ce0-bbe7-b5c775c5a3ae-28167735 I have the same concern on great white (red triangle south of San Francisco) but as diver staying at bottom we're much better luck than surfers...

[@icuppu2]

The best shark defense is to stay out of the water. There are more deaths on humans by dogs than there are shark bites, not shark kills, only bites It is far more dangerously to drive to a destination, statistically, than there is to fly there. Sharks don't get pissed off, they are eating machines and if you annoy them, they get hungrier or swim away as they do by dolphins. If a shark gets you, you won't know until he bites. If you are aware of its presence, swim towards it and his defensive mechanism will kick in because his genetic programming says that no stupid species would do what you are doing because they would not procreate and reproduce, so you must be a predator rather than a stupid prey that somehow escaped evolution of the most adaptable, and not the strongest and the fittest. We only lost one seal diver to a shark, and that is because he was provoking it. He should have just provoked it once to show his predator, but since he moved slower than the great white, the great white nibbled on him, similar to how a dog smells you to get to know who, what you are. Just because you are paranoid does not mean that you are not being followed. Teach your boy the eating habits of sharks and the actions they look for, like running or swimming away, which is a dead giveaway to a prey, most importantly, teach your boy the math, physics of scuba diving because we loose thousands of divers by not doing the math than by shark bites.

[@ScubaGirl68]

There is and always will be a competitive streak between whether to use cu ft or litres. Personally, I learnt with litres and know how quick and easy the metric system makes for calculations in diving. It's also fun to see some misunderstanding between yoke/A-clamp/International fittings and DIN. 80 cu ft is actually equivalent to 11.2 litres 3,000 psi is equivalent to 206 BAR (206.84 BAR for those that need the extra breath or two) 232 BAR is about 3364 psi There are a variety of other ways to show how much the cylinder/tank should be filled to outside the USA. WP = Working Pressure CP = Charge Pressure The Test Pressure is calculated differently too. It is 1.5 times the working pressure. So a 232 BAR cylinder will have a test pressure of 348 BAR and a 300 BAR cylinder will have a test pressure of 450 BAR. As shown in the video, when the cylinder valve is a DIN valve, you can use an "Insert" or "Doughnut" to convert it for use with a yoke 1st stage. If someone has a DIN 1st stage, then they will need an A-Clamp adapter so that their DIN regs can be used on the Yoke style cylinder valve. Yoke/A-Clamp/International clamps are only rated to 232 BAR or 3,000 PSI. Should you want to use a 300 BAR cylinder you will need the right style of DIN fitting on your 1st stage. That's right, there is a slight variation or two for DIN fittings with a 300 BAR cylinder. Finally, as you know, overfilling a cylinder is not a good idea. Sure you might get away with it, but it will shorten the life of the cylinder and it could explode at the filling station.

[@alaind831]

> 80 cu ft is actually equivalent to 11.2 litres no it's not in general - you are assuming a set pressure. 80cf is the available air to breath, doesn't say anything about volume x pressure. The common 80cf ALU tank is MUCH larger (overall size and inside volume) than my 80cf HP steel tank - yet both are the same breathing time/air volume - my HP 100cf are very similar to that ALu tank actually yet 25% more air. Of course my HP are 3442psi vs 3000psi (and steel vs ALU, the latter having thicker walls). also Alec has couple video on DIN - like kzbin.info/www/bejne/Z6bZgH5sorqrorc

[@ScubaGirl68]

Ok, let's get specific then... If I had a steel cylinder made to a capacity of 11.2 litres and filled it to 206 BAR, then it will have the same contents as an 80 cu ft tank filled to 3,000 PSI. Also, a 10 ltr cylinder filled to 230 BAR has the same capacity too. (I'll let you calculate that one) A 12 ltr cylinder filled to 232 BAR is therefore similar, but not the same as, an 80cu ft tank. The 12 ltr will have more gas. The other issue for me is that calling it an 80cu ft tank has the danger of misleading people into believing that is how much gas will be inside. All too often when you get a short fill, so you won't get 200 BAR, but more likely something between 180-195 BAR.

[@AlecPeirceScuba_SeaHunter]

You answered your own question with respect to which system is easier. It depends on which system you were taught, that you have used and with which you are adept. So, I was a math teacher and I agree that the Metric system has some great benefits with respect to moving up or down the scale of the multiple. But, I was raised on the British system and do everything in that system, even today when many measurements have converted to Metric. It's simply quicker and easier - for me. And, at my age, I have no incentive to change. Every example you give using the metric system has its equivalent in the British system and can be as easily demonstrated by a diver adept in that system. This discussion is like steel tanks vs aluminum tanks, DIN vs Yoke, Stab Jacket vs Wing, Rockets vs new design, and so on. There is no answer. BTW, how dumb is it to measure car mileage in liters/100 kms?? I use miles per gallon, or you could use kms per gallon if you like or even kms per liter. Liters/100 kms is silly. I don't want to know how many liters I need to go 100kms. I want to know how far I can go with what I have in the tank. Why don't we all go diving?!! Take care guys. Alec

[@alaind831]

@@ScubaGirl68 > ...will have the same contents as an 80 cu ft tank filled to 3,000 PSI. you don't need to say "filled to 3000 psi" as 80cf IS THE CONTENT (assuming it's filled to proper spec, which varies from tank to tank (alu vs steel example I gave you) and yes shops might short change you, or overfill.. regardless pressure drops a lot when entering cold waters around here, so how much air you have becomes a variable anyway...

[@troop1026]

What is there to say my friend another great video.

[@AlecPeirceScuba_SeaHunter]

Thanks Mike. How's the weather in Montana? Alec

[@troop1026]

Alec Peirce Scuba -19c this morning my friend. Cold cold cold. But that is Montana.

[@Skunkiboi]

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.

[@AlecPeirceScuba_SeaHunter]

Thanks for that information Skunki, was not aware of that. Take care. Alec

[@alaind831]

that's really the difference between an ALU tank (typically 3000psi) and a HP steel tank (3500psi) - has all to do with metal buoyancy and thickness needed for that pressure (thinner walls on steel). Empty ALU floats, while empty steel still sink (yet are lighter on land - run the numbers!). I only dive HP steel for hat reason.

[@arl7138]

So a N. American 80 cu. ft. Aluminum tanks liquid capacity is 11,1 L?

[@Bierstadt54]

Good video - I like the water volume measuring approach myself. Measuring based on rated fill level is convenient most of the time; until mixing lp tanks and aluminium tanks and hp tanks and suddenly it is a lot more confusing.

[@AlecPeirceScuba_SeaHunter]

So a 15 litre tank holds 15 litres of water. How is that bit of information important? Alec

[@Bierstadt54]

Alec Peirce Scuba It indicates the physical size of the tank. I prefer to start there with the static figure for the tank capacity and then go to the dynamic component, which is the tank pressure. If all tanks were always filled to exactly 3000 psi that would be one thing, but they rarely are in my experience. Steel tanks have multiple pressure ratings depending on the tank. I like knowing exactly how much air I am diving with, and that is just easier when you start with physical tank size.

[@alaind831]

"how much air I am diving with" is not spelled out with just 12L vs 15L only... means nothing without working pressure, right ? I think you assume a working pressure and steel, then of course given 12L vs 15L or other sizes will relate to what you have used before and can compensate...

[@Bierstadt54]

Alain Dumesny Of course. One always has to do the math. Either that or forgo gas planning beyond the basic "head up at x psi" that normally is done. I like more gas planning than that.

[@bloodymarvelous4790]

Erm no... Americans don't designate how much air is in the tank, but how much air CAN be in the tank. An 80 cubic foot cylinder CAN hold 80 cubic feet, but it can ALSO be less. When you have an 80 cu ft cylinder at 3000 psi, and you put 2500 psi in the tank, you have 2500/3000 * 80 = 67 cu ft of air. When you put 2000 psi in the tank, you have 2000/3000 * 80 = 53 cu ft of air. When you put 1500 psi in the tank, you have 1500/3000 * 80 = 40 cu ft of air. A 12 liter tank is always 12 liters. When you put 200 bar in the tank, it contains 12 * 200 = 2400 liters of air. When you put 150 bar in the tank, it contains 12 * 150 = 1800 liters of air. When you put 300 bar in the tank, it contains 12 * 300 = 3600 liters of air. This may seem odd to Americans because you have an unmanageable system of units. The rest of the world has moved from weird units to the metric system, because it makes sense. Air pressure at sea level is 1 bar. That is a helluva lot easier to work with than 14.5 psi. 10 meters of water submerged equals 1 bar. Again, a lot easier to work with than 33 feet of water submerged equaling 14.5 psi. You may think the imperial system makes more sense than metric, but it doesn't. How many inches are in a mile? 63,360. How many centimeters are in kilometer? 100,000. That's a nice round number. What's your PPO2 on air at 20 feet? That's (20/33 + 1) * 0.21 = 0.337. What's your PPO2 on air at 5 meters? That's 1.5 * 0.21 = 0.315. That's a nice, simple equation.

[@AlecPeirceScuba_SeaHunter]

Thanks for sharing the math with everyone. Should help anyone who needs data to the decimal point. A

[@pucioy]

Thanks for video Alec. One more point of confusion - In Europe high pressure means something else than in States. Beacuse of using DIN system high pressure for me is 300 Bar not 232 Bar, like in States. 300 Bar tanks are of course heavier and it is rare that any dive center will fill it up to that pressure ( usually they do 270 Bar) and for winter diving I just bought 232 Bar tank beacuse of safety ( lower pressure - lower possibility of frozen 1st stage but I equal capacity buying big 18l tank with double valve for two 1st stages).

[@AlecPeirceScuba_SeaHunter]

HP tanks, anything above 3442 psi must use HP DIN connectors (ie 7 threads). In North America, tanks like this are not common and many dive shops are not setup to fill to the full working pressure. Many divers prefer to use 2 tanks than one HP except for specialized purposes and profiles. Thanks for sharing.

[@DEVINE.IMAGE.]

If you asked me if i wanted a 80cf tank i would not know what size that would be but a 15ltr is a tank i use

[@Bierstadt54]

Alec, when you get some time could you do a video covering all the lp and hp steel tanks? lp tanks seem to owe a lot of their popularity to overfilling to 3k+ psi, and that doesn't seem quite kosher. But obviously a lot of divers think otherwise and have experience to back it up. So...?

[@AlecPeirceScuba_SeaHunter]

Filling a tank beyond its working pressure is a non-starter. It's illegal for a dive store to do it; it shortens the tank life; it places the tank, o-rings, valve and safety blow-out under stress. Why not simply get a tank that suits your purposes? Putting knobby tires on a Honda Civic does not make it an off-road vehicle. Someone is going to get hurt. Alec

[@Bierstadt54]

Well, that is pretty much what I am asking. It doesn't seem like a good idea for the reasons you mention, and yet it is pretty much the norm for Florida cave divers. Obviously these are very experienced technical divers who are not making their tank decisions lightly. I know that many of them use overfilled lp tanks, but I would like to know why. Valve, o-rings, and safety blowout are all going to be the same hp-rated items as on the hp tanks; only the tank itself is going to be under significantly more pressure then it is rated to. Why not buy an hp100 instead of an overfilled lp85? It can't just be the cost, right? Why are lp tanks popular when a diver could buy a hp tank that is rated to the pressure the diver wants to use? This is what I want to know. Thank you.

[@alaind831]

I think I know why. I recently sold a double 85 LP faber 2400psi DIN (picked up during a garage sale among other dive gear) and was wondering why it was so easy to sell and why would anyone use LP steel (I use HP steel) given their lesser buoyancy specs. Well turns out that specific Faber tanks sold in the US as 2400psi (or maybe they were 2200+ rated) are the exact same tanks used in Europe at 220/230bar so tech dive shops in the know will fill it to 3300psi instead of stated 2400. Apparently faber didn't go through the costly process to relabel them for north america. At least that's what the tech diver who bought it told me.

[@JakkM]

Not all the DIN valves can be transformed to yoke by an insert: the valves that go in a high pressure steel cylinder (which has an OP of 300 bar, as opposed to 232 bar) are slightly longer: they have 7 threads as opposed to 5. DIN regulators can go on either valve, but the valves on a 300 bar cylinder can never be converted to yoke. Moreover, not all 232 bar, 5 thread, valves can be converted to yoke by an insert (they also need to have a small dimple on the back do to so), though most do. So actually DIN regulators are more versatile: if you have a DIN regulator + yoke-to-DIN adapter you can essentially use any cylinder, but the opposite is never true.

[@AlecPeirceScuba_SeaHunter]

Ok. So you're telling me that there are 2 different DIN valves, each requiring a different adapter to use a yoke on them (you're quite right by the way). How is that easier than a yoke valve? A yoke is a yoke. I think the yoke's on you. The most versatile system is a yoke adapter on a 300 BAR DIN regulator. That can be instantly fitted to a yoke valve, 200 BAR DIN valve or 300 BAR DIN valve. So you're not changing the tank valve but the reg fitting. Much quicker and easier. Alec

[@JakkM]

You are certainly right, a yoke-to-DIN adapter plus a DIN regulator is the most versatile (in practice all DIN regulators are 300 bar). The reverse, a 300 bar DIN-to-yoke adaptor is not supposed to exist (since it would allow you to fit a yoke regulator, not designed to handle 300 bar, on a 300 bar cylinder), but apparently there are some home-brew models out there. BTW, the DIN story is actually even more complicated than just 232 vs 300 bar: there is another standard for DIN valves, that was designed to be used for nitrox mixes (to prevent people from diving nitrox while thinking it was air). It is essentially exactly like the standard DIN setup, but the valves have a wider diameter (this is normally referred to as M26). The diving community seems to have largely interpreted this (quite correctly) as a bureaucrat solution to a problem that doesn't exist, and very few people use these, but they are out there. Adapters to "standard" DIN exist, but not to yoke. So to have a regulator set that can truly be used on any kind of cylinder you should have a 300 bar (standard) DIN regulator, together with a yoke-to-DIN adapter and an M2- to-DIN adapter...

[@alaind831]

> there is another standard for DIN valves, that was designed to be used for nitrox mixes (to prevent people from diving nitrox while thinking it was air) > wider diameter (this is normally referred to as M26) I wonder if that is what I ran into in France while renting some 15L nitrox tanks. We had to use DIN adapters to use their DIN regulators - I assumed they were DIN300 to DIN200 length issue, but didn't check carefully. thought it odd only the nitrox tank needed those and that they rental regulator were maybe not DIN300. Hummm...

[@Lawdwarf]

@@alaind831 stupid old laws. any air with oxygen over 22% is treated as pure oxygen and must be stored in separate kind of tanks that must not allow to be used by the same regulators as standard air

[@alaind831]

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.

[@AlecPeirceScuba_SeaHunter]

I strongly suspect that all current steel tanks can easily handle 3500psi and more. However, to satisfy divers, they stamp them 3442 so yokers can use them. It simply opens the market to a lot more divers. The difference in amount of air is almost unmeasurable so, why not? Alec

[@alaind831]

I'm just surprised they list them 232 bar and not higher, or some round number say 250, given that most euro diver probably uses DIN anyway and they don't have the US 3442psi (237bar) restrictions of Yoke (

[@ScubaGirl68]

@@alaind831 different manufacturers and the cylinders/tanks will be made to the specific working pressure which is stamped on it. I prefer the pressure to be in BAR but I also know that 3,000 psi is equivalent to 206 BAR.

[@alaind831]

@@ScubaGirl68 what Alec and I are saying is that the manufacturer very likely has the same mold and fabrication, but stamps it differently for different markets... would make $$ sense

[@ScubaGirl68]

@@alaind831 The testing procedures are very different in the USA to those adopted within Europe. I'm acutely aware that should someone present a tank stamped "DOT" to a fill station in the UK, that they are unlikely to get it filled. Certainly, as Faber are now exporting their product to the USA it might be confusing, but without someone from Faber confirming one way or the other, I know enough to know that the USA has some very different manufacturing requirements to Europe. If Faber are making tanks for the USA market, then it is possible that they are using a different specification of metal for that market. The test procedures at the factory may also differ. As for filling a 232 BAR cylinder to 240 BAR and allowing it to cool down to about 230 BAR, I would argue that this depends on the specific markings on the cylinder. There was a bulletin issued in the '90s which clarified that a cylinder marked "CP" should not be filled above the "Charging Pressure". However one marked "WP" could be filled above the "Working Pressure" with the intention that it cools down to the working pressure before use. There may have been an amendment issued to relax things since then, but I haven't seen such a document.

[@nickbaldus]

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

[@AlecPeirceScuba_SeaHunter]

Garmin GPS products are popular here but not their watches, wrist timers, or the newer dive computers. There are literally dozens of similar well-proven products on the market from well-known scuba gear companies that offer all the same features and more for less money. The GPS feature is the only area in which the Descent Mk 1 excels of course, and that's only usable on the surface. I'm not discounting it entirely but it's not enough of a biggie to make your decision. Air integration is universally available now with almost all dive computers and that IS biggie. What could be more important that having a computer that measures your air consumption and tells you at all times how much longer you can stay down? And all other dive computers offer exactly what the Garmin does. Personally I don't like the small wrist-watch style dive computers (although I'm currently using one!). In clear, warm water they are easy to read but in any low vis conditions like cold, fresh water lakes, they are tough to get the info you want quickly. So it also depends a bit on what dive conditions you enjoy - or don't enjoy! Spend some time in your LDS looking at and trying on different dive computers. A good dive store will let you try some or arrange to borrow one from an staff member for you to try. Once you've actually used it underwater, the answer will come to you. Also don't be sold by a long list of 'available features'. Similar to cell phones, you will find that you use a tiny fraction of all it's capabilities - but you pay for them all up front and they can make accessing information a tedious process while also complicating the device. BTW, I like Garmin and use their GPS in my car, while hunting, camping, etc. I didn't know until recently that they'd started to enter the dive market. They have a lot of catching up to do. I hope this helps. Alec

[@cajicoutinho3899]

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

[@ScubaGirl68]

The answer very much depends on your own breathing rate. This can and does vary but many agencies give a starting figure of 25lt/min for at the surface to help you to work things out. You then take the depth and work out the ambient pressure. The ambient pressure at the surface is 1 BAR. Every 10m of depth you add 1 BAR. The ambient pressure at 15m is 2.5BAR. The calculation would, therefore, look like this: 25lt/min * 2.5 BAR = consumption rate = 62.5 litres per min Now you need to work out how much gas you have in that 12ltr cylinder. Simply multiply the capacity by the pressure. So assuming it is filled to 230 BAR, then it would look like this: 12ltr x 230 BAR = 2760 litres Finally, divide 2760 by 62.5 litres. This gives you just over 44 minutes at 15m. Ok, there are some important things to add, but hopefully, you get the idea. So what are the important things to add? First of all, you should always keep a reserve. Some will say that you should surface with 50 BAR, others will argue 1/3rd. Next, you need to include the time it will take you to get from the surface to the bottom, then add the time it takes you to get from the bottom to your first stop. You then have to work out how much gas you're going to breathe at the stop (safety or mandatory stop) and then from the stop to the surface. So, assuming that you want to surface with 50 BAR and stop at 5m for 3 mins, the planned time you can be underwater with your 12 ltr cylinder at 15m has dropped significantly. Of course, none of this takes into account any required decompression stops or no-stop dive times. Please consult your dive tables and/or dive computer for that information.

[@Oli4Post]

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 180x12 = 2160 liters. Still easy. And when I have a 10 liter the number of available air is 10x180=1800 liter or 10x232=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.

[@AlecPeirceScuba_SeaHunter]

Thanks for watching Oli. I re-read your post several times and I think I finally got the idea. Doing so brought 2 things to mind: 1. darn I'm glad I use an air-integrated computer. It tells me exactly how long my air will last at any time, any depth. 2. what a diver finds easy to use (hence the best system) will depend largely on how he was trained and is accustomed to. That is, while your explanation is good and it seems to make sense, I would find it very hard to apply after so many years of using cubic feet pressure to determine remaining air. I think our systems are the same but with different units. It's a bit like Celcius versus Fahrenheit. There's no way I'd feel comfortable in my house if the temperature is 21 degrees - 71 degrees is OK but not 21!! Mind you it could be my age too. Thanks for watching and for your input. I'm sure a lot of my European viewers found it worthwhile. Alec

[@glennlooper4840]

I never really do in water gas planning. I pre plan my dives. With the cuft rating of a tank it is simple as well. divide the tank size (cuft) by the rated pressure and you get the tank constant. Once you know this constant then multiply it by the psi in your tank. and that is your cuft. For example take the very common AL80 rated at 3000 psi. 80/3000=.026. If i only have 2800 in my tank after it cools then i have 74.6 cuft of air. Granted this may require a calculator, but i usually have my cell phone that has a calculator built in. and i usually plan my dives beforehand. I try not to go all willy nilly half cocked jumping in the water. But if i did, i could use my slate to multiply things out by hand if i was really that curious. Like they say, plan the dive and dive the plan (know your available gas, sac, planned depth, etc).

[@DontScareTheFish]

The other point Oli didn't cover is when teaching diving with the metric system most of the math gets simpler because the units mostly cancel out and in most situations you're left with just a number. If you've had a good instructor (teaching you how you can make the numbers smaller first rather than multiplying into big numbers and then trying to divide them) you're always dealing with small numbers which can be done in your head. The cylinder volume is measured in liters. Your breathing rate is measures in liters per minute. The liters cancel each other out and you're left with minutes. Pressure weather in your tank or due to depth is always in bar, so the units cancel and you're left with a number. While the depth is measured in meters, when thinking about air usage you talk in absolute pressure in bar. At the surface we're at 1 bar and for every 10 meters we add another bar. So we just divide the depth by 10 and add 1. Now if I was was to go to 25 meters to get the pressure you would be breathing at at 25 meters (just over 80ft) is 3.5 bar (25/10 = 2.5 for the depth and 1 for the surface). If my SAC rate is 18 liters / min and I have a 12 liter cylinder I know I would breathe 1.5 bars per minute. Assuming a standard 50 bar reserve the above 200bar @12L gives me 150bar of "usable" air divided by my 1.5 bars /min gives 100 mins (usage at the surface) divided by 3.5 (for the depth) gives a little over 25 mins of dive time ignoring you use less air on a deco / safety stop. At any point in my dive I can look at my contents gauge (in bar) and get a good idea of how many minutes of gas I have left in my tank. Instead of using 1.5 and 3.5 per above I'll either think 2 & 4 or multiply them together and just think 6 so if I had 120 bar in my 12L tank I'd have a little over 10 mins before hitting my reserve. How does that compare to the imperial system with it's CuFt and PSI etc?

[@alaind831]

Timothy, I get why planning is simpler with smaller number as you describe above (and having been raised on metric, but living with stupid imperial). The one thing that's nice about how they measure air volume in the US is that you KNOW a 100cf tank has 25% more air than a 80cf rated tank. Simple as that! so it makes switching easier if you know you're gonna consume more (hunt vs take photo, etc..). Those tanks could use very different pressures (commonly 3000psi, but there are many 3300psi alu tanks, or HP 3442/3500psi steel tanks) doesn't matter. In the 12L vs 15L tank, you have to compare rated pressure to see relative sizes of air. In both cases you need to know the actual fill pressure to know the % of the ideal air volume you are getting... usually less but sometimes you're lucky and get an overfill :)

[@DontScareTheFish]

"you KNOW a 100cf tank has 25% more air than a 80cf rated tank" Are all the 80cf / 100cf tanks measured to the same psi eg 3000 psi or are some 100cf tanks physically smaller but rated to higher pressures ? I was under the possibly false impression that just like in Europe you can get higher pressure cylinders. In Europe cylinders are generally 232 bar, but you can get 300bar cylinders too. I see your point about the 100cf vs 80cf cylinder. The same can be said about a 10L vs 12L vs 15L. I know a 12L tank is 20% bigger than 10L. When teaching in the metric system you always calculate the volume gas in the cylinder by volume x pressure so you're never lured into the false sense of "I have a 100cf cylinder so I must have 100cf of gas"

[@cajicoutinho3899]

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

[@rickycarter6371]

A hood will keep water from flowing in and out of the ear. Some people have to descend a little slower. You might want to try to equalize more, and if you start to feel discomfort you can ascend a little equalize and then start to descend again. It's also a good idea to practice equalizing even before you get in the water to get your ears used to it. Nasal decongestants help also, anything that will dry up your sinuses. Hopefully this helps. Have fun, and be safe!

[@ozjohnno]

great vid as always mate, but where is Desiree ?

[@AlecPeirceScuba_SeaHunter]

Don't get me into that hornet's nest again!! Funny how an attractive girl can bring out the worst in some people. I'll bet even that statement will raise hackles. Thanks for watching John. Alec

[@owenmougenot712]

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

[@AlecPeirceScuba_SeaHunter]

Most SPGs have color-coded dials - green for lots of air, yellow for getting low and red for 'Go Up'. It's a universal language and should be understood by everyone. Start checking out an Air-Integrated computer. After the usual first reservations (I'm an old, old diver!), I love it now. It shows your remaining air pressure, it shows how long that remaining air will last at the current diving conditions (depth, effort, etc) AND it alerts you with flashes and/or beeps when you're getting low. Perfect for inattentive divers or dumb divemasters. Take care. Alec

[@owenmougenot712]

Thanks for the suggestions, yes us "old" (I mean, experienced and worldly) guys tend to adapt to new things cautiously (what's wrong with my beta-max video player?) I just watched seahunt 2-27 the getaway and noticed that tank mounted propulsion unit and also the "porta-sub" that he has used before, this might be an interesting topic for your vintage scuba series the various things that led to the current diver propulsion devices like sea-doo makes. Keep the videos coming Thanks Owen m

[@alaind831]

I recently took my computer to europe and switched the units to bar/m to make it easier with other divers (not that others would check mine and tell me what to do). That's nice thing about computer - adapt. Surprised they didn't see yellow/red in your analog pressure gauge.

[@JACKMB594]

If you know it's not the local unit, why don't you convert it? Only takes a moment to work out approximately many bar you have.

[@sparkyobrian6417]

dive gear express sells spg's that have bar and psi on sane gauge face.

[@mvakkilainen]

The reason for the OP on the tank is because there are 2 different pressures used in Europe 200/232 Bar & 300 Bar. The OP is clearly marked on the tank so that the Diver can calculate the air in the tank accurately.

[@AlecPeirceScuba_SeaHunter]

I'm not sure how knowing the OP helps the diver calculate the air in the tank. The air capacity depends on the tank capacity. That's why knowing the air capacity of a full tank i.e. 80 cubic feet, is useful. I think the OP is there to ensure the tank is not overfilled. Alec

[@mvakkilainen]

Hello, The OP is to tell the diver at what pressure the tank should be after filling and what the setting on the compressor should be. The calculation here in Europe are for lets say a 12l 200bar are 12L*200bar = 2400L of air / my air consumption about 24L/minute = 100 minutes of max air at 1bar or surface and 50 minutes at 2bar or 10 meter depth. this makes making a dive plan and calculation relatively simple. Or at least for me. Our compressors here are normally fitted with overflow valves that are set at about 220 and 310 bar to make sure over filling is almost impossible.

[@alaind831]

300 bar (4350psi) god goodness, who makes and especially where can you get such a fill :) ? I feel so inadequate with my 237 bar tanks...

[@hanskuijsten2380]

@@alaind831 I don't know where you're from, but here in the Netherlands allmost all divecentres can fill 300 bar.

[@alaind831]

@@hanskuijsten2380 nice! yeah in the US we can't buy 300bar tanks (usually 237bar at most which can still take Yoke - likely the reason) let alone get that kind of fill (firefighter carbon tanks are that high I believe so they must have fill stations for those). Even when I was in France last summer it was hard to get a good 230bar bar fill...

[@amirkhan-fw4fk]

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

[@AlecPeirceScuba_SeaHunter]

It's a very common problem Amir. So common that there have been several devices introduced over the years to combat it. Unfortunately, none have been really successful. The problem comes from the fact that the air you are breathing is very dry. It's dry on purpose. When scuba breathing air is produced, the water is removed (almost all, can't get it all out) so as you dive your mouth slowly gets drier and drier. Some divers suffer more than others of course. Since the devices offered don't really help all you can do is have a good long drink of water just before the dive and have more water ready when you surface. One of the benefits of diving in fresh water is that you can take little sips occasionally. That's NOT recommended if diving in the ocean. Hope this helps. Alec

[@user46346bdtgry]

A tip I heard is to take the reg out and take a mouthful of sea water, swish it around & spit it out. The salty water will get you salivating like mad! (wouldn’t really recommend it myself for obvious reasons but you’re an adult, so your decision)

[@alaind831]

My regulator breathes a little wet (or used to) when completely upside down - couldn't you use that (or take mouth piece off and put it back) to get a little bit of moisture back in (alas salty) ?

[@un_lucio]

That "cubic feet" air you're talking about must stink horribly of blue cheese and used socks ;P BTW: the whole world uses that system (AK SI units), it's the people in North America that for some reason didn't get the update memo and are still stuck in the middle ages :P come guys, join the fun: it's easier I promise :D

[@AlecPeirceScuba_SeaHunter]

North America is different in many ways and we tend to value our uniqueness. While any sensible person will acknowledge the benefits of the metric system, that doesn't mean we will adopt it without resisting. No sane person would drive on the right-hand side of the road either but I understand lots do. Take care. Alec

[@alaind831]

Alec spoken like a true Canadian on the 'uniqueness' - kinda hard when you are surrounded by the US...

[@fxpmike]

@@alaind831 That's true and apply as well for Mexico, i'm watching this video because i'm doing my SSI advanced open water but the only version in spanish they have it is the one from Spain, so they talk about bars and tanks in liters and i get really confused because here in Mexico being surrounded by the U.S. we are used to psi's and tanks in cubic feets (at least for scuba, and how we fill our tires... and also we buy paint in gallons... and our tools measurement are on inches... we are doomed)

[@alaind831]

@@fxpmike didn't realize mexico was using imperial system... I feel for you guys.

[@fxpmike]

@@alaind831 It isn't the everyday system but it has found the ways in technical and industrial aspects

[@mdovideo1414]

What is the biggest size tank you have seen

[@AlecPeirceScuba_SeaHunter]

In portable tanks, once you get to 100 cubic feet you've pretty much maxed out. For more air you have to add more tanks. I have had three 72 cf tanks on my back for a total of 216 cubic feet but it's barely manageable on your own until you get into the water. I have partially completed a very large diver tank set-up and hope to complete it sometime in the near future. It will have over 400 cubic feet of air!! I'll certainly let you know how it works. Alec

[@alaind831]

If you go HP steel tanks (which have much better buoyancy than ALU tanks) you can get 130cf/17l (faber) per tank which my friend has. I own a 120cf/15.3l worthinton which I use when hunting and it's quite manageable... my main tank are 100HP/13l steel version of the same (which are same size as 80cf Alu yet require less overall weight for 25% more air!). I sold a double 2x120HP of my tank to someone, as well as 2x85LP - both of which are quite heavy... with lead bars as you can loose 15# or more of air when going empty! I started with doubles back in the late 70s but the new HP single are plenty for me now...

[@joediver7669]

There are 130cuft 3442psi tanks that can be plus rated 10% above OP so about 140cuft. I used to do 2 hours dives on mine.

[@Skunkiboi]

Biggest tanks I've ever seen were Double-18 L at the Attersee, Austria. My Double-12 L looked so small and insignificant compared to them.

[@anthony9thompson]

An Abrams

[@mdovideo1414]

Can you rent a 100cf aluminum tank

[@AlecPeirceScuba_SeaHunter]

Sure. Some stores have them, some don't, but if you call and arrange for it in advance, they can get one for your to use. Kevin does exactly that when he's on a dive trip. Alec

[@TreVox]

hahahahaha kevin oh kevin.

[@theveryfirst]

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.

[@AlecPeirceScuba_SeaHunter]

Thanks for watching. In Canada we are fully metric except all my devices are still imperial (i'm old). Not wanting to start a battle with this video, but divers who cross continents don't always understand the different preferences and measurement systems. Safe diving my friend. Alec

[@sparkyobrian6417]

I have both and in addition I have 300 bar din regs which I can use on both 300 and 232 din bottles, granted most shops here in my area dont fill to hp sadly.

[@kathyweigelhi-lophotovideo2984]

Do other countries use nitrox?

[@djsalose]

LA5150 er do in sweden,

[@AlecPeirceScuba_SeaHunter]

I can't state for sure but, all divers have access to the internet so, even if they are not taught Nitrox, I'm sure they know about it and can or will get it. Certainly in North America, the Caribbean, South America, UK, Europe, Mediterranean, Red Sea, Australia and the entire South Pacific, Japan, Korea. What else is there? I think it's safe to say that it's everywhere. Availability in all these locations may vary. Alec

[@shaunduvenage]

Thats my local dive shop you are at.

[@AlecPeirceScuba_SeaHunter]

That's cool. Had a great time in South Africa but the first 2 days of diving were cancelled due to huge waves.

[@KimonFrousios]

I think separating the size of the tank from the pressure of the air in it is more sensible, because the same amount of breathable air can be achieved with different tank volumes and air pressures and that affects the amount of weight you need to carry.

[@AlecPeirceScuba_SeaHunter]

I agree, I think. The most useful measure of a tank is the amount of available air - not the pressure, size or weight. If you know how much air the tank holds when full, you know how long it will last. That's why 80 cubic feet rather than 15 litre is better. At normal breathing rate of 1 cubic foot of air per minute, an 80 will last 80 minutes. 15 litre is amount of water that tank will hold. What good is that information?? Alec

[@alaind831]

kimon, I disagree. #1 you want to know how long you will last so available air is critical. #2 you need to look at buoyancy spec to see how much lead you need. Just because it's 12L tank doesn't tell you how much air without checking WP. Nor does it tell you if it's made of steal or Alu, if low pressure (thinner wall) or High pressure (heavier) all of which affect how they sink... 80cf at least tell you #1 part. Now I HATE imperial system...but at least I get a volume of air without any calculations...

[@wgo100]

Metric (should) rule(s); metric=logic

[@AlecPeirceScuba_SeaHunter]

Scuba diving isn't logical. Alec

[@johnthomas2070]

Literal thinkers. DIN regulators

[@AlecPeirceScuba_SeaHunter]

Conservatives love yokes. Alec

[@robbiemify]

What's a liter ??? is it anything like a litre ????

[@AlecPeirceScuba_SeaHunter]

Almost the same. You must get confused by cubic feet vs litres too Robbie. We should all agree to measure tanks based on how long the air will last at 30'. Or is that 9m? Alec

[@pucioy]

1 liter is 10cmx10cmx10cm and 1liter of pure water weights 1 kg

[@jetfire245]

Good god. Screw using liters to measure tanks, that makes no sense at all.

[@djsalose]

why?

[@thefooooob]

Haha you never had to plan a dive have you? Ever had to calculate minimum pressures, turn pressures, etc? Simple example: 15L tank at 1bar has 15L of air in it. 15L tank at 2bar has 30L of air in it. 15L tank at 100 bar has 1500L of air in it. Now do that in cubic feet and psi and report back whether it's easier, the same, or harder. And all this without yet including the fact that an AL80 tank doesn't actually have 80 cubic feet of air at the rated pressure.

[@AlecPeirceScuba_SeaHunter]

Actually it does - or very close. However, I think the point is that knowing how many litres a tank has in it doesn't help you calculate the remaining time. So to your challenge - an 80 cubic foot tank has 80 cubic feet when full. Couldn't be easier. And if you know how much air you consume per minute (generally around 1 cubic foot at the surface), it's supremely easy to know how long the tank will last.

[@jetfire245]

thefooooob that's why I have a problem with it I guess

[@jetfire245]

Alec Peirce Scuba that's why I have a problem with it I guess.