Need more gas - now what?

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Dan_P

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As we dive deeper and also use other breathing gases than air, our gas volume needs naturally increase.

Obviously, what's the point in having, say, 30 minutes of no-deco time at 30m, if you only have gas for 20 minutes?

The answer, of course, is to bring more gas.
For probably the vast majority of divers, that means swapping out the original BCD and single-tank, with something else; but what, and why?

Going through a few different options, one will probably at some point encounter a few main categories:

Backmount or Sidemount
Manifold or Independent
High Pressure or Low Pressure connections

They each have pro's and con's, so let's have a quick chat about those - and most importantly, the "why" of things:

 
For most folks looking for more gas, a bigger tank is going to be a better option than BM or SM doubles. There is not much of a learning curve moving from Al80's to steel 120's if you want ~50% more gas.
 
For most folks looking for more gas, a bigger tank is going to be a better option than BM or SM doubles. There is not much of a learning curve moving from Al80's to steel 120's if you want ~50% more gas.

I hear what you're saying.
The most common in metric, is going up from a 12L to 15L, where a 15L is a usual go-to solution when diving to 30m.
That'll last for an air dive to that depth.
But, when we start going further, either looking into tech or simply using nitrox to extend bottom times, that gas will no longer be enough.
That's when it starts making sense to scale up.

On more of a sidenote, I think it makes sense to use from the start a system that scales to cover that eventuality, as both 30m-certifications and nitrox courses are very popular.
 
Sure thing. But six months later, it's entry-level tech, and then we'll be stuck with an extra tank in the garage.
My point is, scalability is a nifty thing, and at some point, the manifold question enters the equation.
 
Don't forget the diver's physical ability to safely pack more gas. It can be different for the same person diving off a boat than off a rocky beach at the bottom of a cliff. Sometimes the best, and most fun, course of action is to stay shallower and/or a shorter time. Even if you can pack the weight, wearing doubles plus 2-4 slung bottles just gets in the way --- not what you want for lobster diving for example.
 
Don't forget the diver's physical ability to safely pack more gas. It can be different for the same person diving off a boat than off a rocky beach at the bottom of a cliff. Sometimes the best, and most fun, course of action is to stay shallower and/or a shorter time. Even if you can pack the weight, wearing doubles plus 2-4 slung bottles just gets in the way --- not what you want for lobster diving for example.

Agreed, the right tool for the job. I giggled at the picture of two tanks plus 2 deco tanks for a lobster hunt :wink:
For me personally, I enjoy diving a system that scales all the way from 1 tank to whatever, on the same "interface". That way, I can bring one tank when that's what I need, and any number of bottom tanks plus deco tanks, when I need those - and swap them in-water.
I mention this in the video, when addressing low-pressure connections.

What I’m seeing more and more is divers moving straight to rebreathers.

Then they discover, for deep dives they need bailout cylinders, for when the s**t hits the fan.

It's scary stuff, that. I think we're much in alignment on the perspective on Consequence of Failure versus Probability of Failure, as I mention in the video. To me, it makes a world of sense to have a solution in place for a single failure, even if it is not the most probable failure (in your example, any CCR related one).
 
I have AL80s, HP100s, HP117s, and a brand new HP130. I fit the tank to the dive. For added capacity, I have an AL40 I can sling either as extra capacity or bailout depending on the dive. I have also dived using a HP150, and know people who use them regularly. If sufficient gas volume to do the bottom time is the criteria, there is no need to go to doubles, single tank diving is quite viable. A regularly done local dive sees me using a HP117 and finishing an hour or more later with 1,500psi. I would not use a HP130 or HP150 for that. My son will use a HP100 on the same dive because he doesn't breathe. We like the reserve on those dives. The dive I did with the HP150 was one normally done either as a boat dive or as a shore dive but often with a DPV. We did it as a looooooong swimout shore dive submerged as we were going into the shipping channel. Doubles would not have provided more gas.

Our diving regularly includes wreck diving to 30M on EAN32 with ample gas in our large tanks to make use of our allowed NDL.
 
I have AL80s, HP100s, HP117s, and a brand new HP130. I fit the tank to the dive. For added capacity, I have an AL40 I can sling either as extra capacity or bailout depending on the dive. I have also dived using a HP150, and know people who use them regularly. If sufficient gas volume to do the bottom time is the criteria, there is no need to go to doubles, single tank diving is quite viable. A regularly done local dive sees me using a HP117 and finishing an hour or more later with 1,500psi. I would not use a HP130 or HP150 for that. My son will use a HP100 on the same dive because he doesn't breathe. We like the reserve on those dives. The dive I did with the HP150 was one normally done either as a boat dive or as a shore dive but often with a DPV. We did it as a looooooong swimout shore dive submerged as we were going into the shipping channel. Doubles would not have provided more gas.

Our diving regularly includes wreck diving to 30M on EAN32 with ample gas in our large tanks to make use of our allowed NDL.

Thanks for your reply.
I can see where you're coming from, and I've been through that view and aspect on dive gear myself, too.
As soon as I started diving, I'd get a full kit, and then when it got a bit colder, I'd add a new wetsuit, but as I went deeper I'd need to add a drysuit instead.
As I needed to position myself more effectively, I'd get different fins from those split ones, progressively larger tanks, going from a BCD to a different solution, you name it.
The issue in that was 1) I didn't get to consistently "recycle" what I was learning and how I was diving, which really made things more cumbersome for me, and 2) I ended up with a tonne of gear that I'd end up selling cheap anyway.
Second-hand marketplaces and, particularly, scuba gear vendors generally love this approach.
For a diver though, it's burdensome and costly.

There's also the aspect of redundancy when entering overhead environments. I wouldn't want to be far inside a shipping lane, wreck or cave, turning at my reserve + 1/3 gas and then have a failure on my only tank - particularly if my team member had been skip breathing an even smaller tank all the way, and we now had to contend with increased gas consumption due to stress.
It stands to reason that one single tank failure would probably end up meaning the whole team needing to surface in that shipping lane, and hope for the best.

For me, I ended up with an isolatable solution that simply has 1 AL80 integrated when I dive within the 18m range, 2 AL80s when I dive within 30m range, 2 80s and a 40 for the 50m range, 3 80s and a 40 in the 60m range, etc., progressively adding more tanks integratable with added depth. Same 2 regulators throughout.
Or, add a rebreather component on top of the same base.
Zero waste and 100% consistency throughout the training path, and dives. I think for me, that made my diving a lot easier.

But, as I mention in the video, there are of course more ways to approach both consistency, redundancy and compartmentalization.
 
https://www.shearwater.com/products/teric/

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