Recommendation for recreational pony bottle size

[herr2720]

I use a AL19 set up to mount to my main tank (it's like my LP98's discordant twin) when I dive solo. With a buddy I'll sling it so it's easy to give away if need be. It creates about a -2lb full with gear that I offset with a 2lb weight in my rear trim pocket. Yes, it creates a little extra drag, but I'm not in a hurry and if I was I'd use a scooter.

For me a 19 is nice as I fill/top it off with a whip off my main tanks so it never really gets to 19 unless it's filled at the LDS, so really it's frequently just a 13-15cf tank, more than enough for me. When I bought it at LP it was only $10 more than the AL13 so it was worth it to me.

 

[tursiops]

I moved the octo from my main to my pony as SDI Solo Diving Course recommends.

SDI Solo course does not actually recommend this. The course recommends (even solo) you dive with standard recreational gear, but add a pony with reg and SPG (or mini-gauge). The course does say, although, you might want to remove the octo from your primary 1st stage, since you are not likely to use it, but that would be *for solo diving only*. The OP does not mention solo diving, so he should keep the octo, and add the pony as a reserve.....not as part of his gas planning.

Anything smaller than a 13 cuft is a waste of time, and a Spare Air is a joke....at best it might get you to your buddy, a few feet away. I have a 13 I only use if I'm traveling by air, and sometimes that is all you can rent. A 19 (as many have said) is the smallest to really give you a reserve, and a 30 would actually give you a 1/3 of your total-gas (assuming an 80 is the back gas) as a reserve. So, 19 or 30 is the usual recommendation, and 13 is acceptable. If I'm teaching the solo class, the student must have at least a 13 (or independent or manifolded doubles) or an H/Y-valve. The SDI class allows a Spare-Air; I don't (instructor prerogative).

As to moving the octo to the pony, I think that is a bad idea, unless you are *always* diving solo. In any mixed team, it is possible to cause more problems than solve them, because the OOG diver does not expect to not find an octo. You might think to move the octo back-and-forth from primary to pony, but every move is a chance for a lost port plug or screwed up o-ring. Why bother? Just add the pony as an independent system.

Right now you can buy a new but old-hydro 13 for $70, with a convertible K-DIN valve for $35 more.

 

[GrumpyOldGuy]

Do you travel by air? If yes, then a 13 is the largest that you can travel easily with.
Do you want you tank to fit in most boat racks? If yes, then the 13 is still the answer (the 19 depends on the boat)
If you want to be sure you have something big enough no matter what, sling a 30 or 40
If you want enough for your described dives, then the 13 will fit your needs.

I have a 6, a 13 and a 30. The 13 is my favorite and gets used often in So Cal. The 6 is really small and takes some serious thought as to what dives I use it for and no safety margin. The Spare Air is a joke. The 30 is a PITA, it is a good size for someone wanting to push to the limits of rec diving and nothing wrong with it outside the hassle of dealing with the bulk top side.

 

[Hatul]

I'd recommend a 13 cu ft for you. It's enough for most situations and still small enough not to interfere too much. It's a compromise.

 

[rhwestfall]

I was gifted a 13, thought it was cool (now I have a 19 - thought it was better, and a 30 - realized what the heck I needed). It (the 13) is basically is my tire service tank, or "training/quarry" tank just so I am always used to a tank being there. i consider it "somewhat inadequate"....... YMMV. Attempting to be safe is never wrong. Just make sure what you are selecting is going to do what you need it to do.

 

[Kharon]

SDI Solo course does not actually recommend this. The course recommends (even solo) you dive with standard recreational gear, but add a pony with reg and SPG (or mini-gauge). The course does say, although, you might want to remove the octo from your primary 1st stage, since you are not likely to use it, but that would be *for solo diving only*.

First they most certainly do recommend this. Page 82 of the SDI Solo Diving Manual: "It is important to note that the solo diver does not need any other type of redundant regulator like an Octopus or Air2. ... By having an Octopus or Air2, the solo diver has two problems the normally would not need to deal with if they didn't have those two pieces of equipment: An unnecessary failure point and extra drag from the equipment they don't need." I would add they also constitute an additional entanglement threat. These same considerations apply diving solo or with a buddy and no where do they say "for solo diving only" nor do they recommend "standard recreational gear". Those are entirely your intimations/extrapolations, and wrong.

As to moving the octo to the pony, I think that is a bad idea, unless you are *always* diving solo. In any mixed team, it is possible to cause more problems than solve them, because the OOG diver does not expect to not find an octo.

Once again, simply wrong. Same page: "Along with the standard way you would normally store an octopus regulator, is the same way you would store your redundant second stage ..." My pony is yellow, the hose is bright neon yellow, the reg is yellow, and the reg holder that is in the exact place anyone would expect to find an octo is bright yellow. What confusion??? More confusion would be caused by having three hoses/regs with two of them yellow octos - making it difficult to know which is the right one to grab or the very atypical Air2 configuration. Virtually no one sees and practices with an Air2 in OW training.

Moreover, once they get the reg in their mouth I can unclip and hand off the pony thus freeing myself from a possibly panicked diver who could bolt to the surface. I don't want an octo tied to me that teathers me to an OOA diver. With the exception of catastrophic equipment failure they have already shown dangerous incompetance.

In short, my rig follows SDI recommendations and works diving solo, with a buddy, and diving either way (solo or buddied up) and running into a random OOA diver from another group.

 

[Rich Keller]

I use a 30 cu/ft because it is more versatile for deeper depths and I can also use it for shallow water shore dives as a primary tank.

 

[Colliam7]

I'm looking to purchase a back up spare breathing pony bottle system for recreational diving here in So. Cal. People have recommended the Spare Air others says go to a 6cf rig and yet others say go for a 13cf. I'm not a tech diver and the deepest I have ever gone is 100, but I usually stay between 40 to max 80 feet max. Any suggestions??? Thanks, Vlad

The answer may depend in part on how people interpret the phrase 'back up spare pony bottle system'. As a preamble, it is fine (and absurdly irrelevant) to say that use of proper gas management and proper buddy skills means you will never need a pony. Proper gas management INCLUDES consideration of a redundant air supply. I may have great buddy skills but be paired either with a complete putz, or someone (like me) who justifiably does not accept that his/her buddy 'owns' any part of their gas supply.

I interpret your statement to mean a redundant air source that will allow you to safely a) terminate your dive, and b) surface, if you have a catastrophic failure of you primary air supply at the most extreme point in your dive (deepest, farthest from the ascent line / surface / whatever. IF that is your goal, then some calculation of how much air it will take to accomplish those objectives is a good basis for determining the needed size. The deepest you have ever gone is 100 ft, so you could use that as an 'extreme point' for planning. Better yet, use the depth limit of recreational diving - 130 ft - as the basis.

Do you know your air consumption rate (SAC/RMV)? If not, use something conservative (i.e. higher than it probably is), say 1 cfm, for planning. The better approach is to measure YOUR specific consumption rate.

At 130 ft, with a SAC of ~1 cfm, you are using ~ 5 cfm. If you have a catastrophic gas supply failure, do you think your gas consumption will remain the same, or possibly increase? That question is a bit of a set up. It probably will go up. Will it double? Will it increase by 25%? Who knows. For planning, why not assume it will increase by 50%, to 1.5 cfm. This is something of a worst case scenario, but why not use the worst case? Hope for the best, plan for the worst.

So, you are at 130 ft, and you have a catastrophic gas supply failure. How much gas do you need in a redundant air supply, to allow you to a) figure out what is happening, then b) begin, sustain, and successfully complete a normal ascent? Figure a minute at depth to change to your redundant air supply, sort things out, get to the ascent line, etc., then 4 minutes to ascend comfortably at 30 ft / min to a safety stop depth, then 3 minutes at the safety stop. VERY roughly, at an assumed increased consumption rate, you may be looking at needing as much as 30 cf. Gas goes quickly when you are under stress, and things are not going well.

Sounds like a lot, sounds like it is probably more than you would actually need. In my own case, I dive with either a 30 cf or a 40 cf pony bottle, as a redundant gas supply. I have never needed it, but that fact has no predictive value for the future. But, IF I need it, I have a redundant supply that makes sense. It may not be enough, or both gas supplies may fail, . . . - the list of statistically improbable outcomes is long. But, I am pretty sure that, diving within recreational limits, I should have an adequate redundant supply to deal with most contingencies.

In reality, your SAC rate may be a bit lower than 1 cfm. In reality, the urgency of a situation such as a catastrophic gas supply failure might drive you to ascend at 60 ft / min (or more), in reality you may decide to blow off the safety stop. You may need less gas. But, if I am going to plan for the worst, I am going to do just that. Otherwise, I will not dive deeper than 60 ft, and I will carry only a 3 cf Spare. (And, in my spare time, I will go to Las Vegas or Atlantic City, and put all my available funds on the table, and HOPE for a big win that will take care of my retirement.)

What size to buy? I see little point in anything less than a 30 cf bottle. If I can absolutely be sure I will not go deeper than 60 ft, I could argue for something smaller. But then, the issue is, why go smaller than 19? With a 19 cf bottle, I can scab the bottle to my main gas supply. I still need to buy the bottle, I still need a regulator for the pony, I still need to VIP it, hydro it., etc. 6 vs 13 vs 19 - it makes almost no difference in cost or 'cumbersomeness'. Moving from 19 to 30 means moving from a bottle attached to you main gas supply, to a slung bottle.

In the end, however, it is entirely up to you. To paraphrase Clint Eastwood, 'Do you feel lucky?'

 

[GrumpyOldGuy]

^^ How do you pack your 30/40 when you travel via airlines?

 

[Aqua-Andy]

Why all this speak of "octo"? The reg that the OOA diver gets should be the one that was just in your mouth, not some reg on a funky colored hose strapped to some random part of your dive system. If you had an equipment issue and lost access to your air would you want the reg they have strapped to them and probably was dragged through the silt? Or would you rather see the reg they were just breathing from being shoved into your mouth? As for the pony just do the math, it's that simple. No point in having a pony if it can't get you back safely. Just don't forget when doing your calculations, when the turd hits the fan you will not be breathing as calmly as when you are relaxed. You may also want to factor in some time to get situated when you have to switch to your back up air supply.