Redundant Air: H Valves, Ponies, Doubles, And The Surface.

[boulderjohn]

You can easily die in shallow water if you have an entanglement hazard combined with out of gas.

Another instructor and I were setting up for a scuba demo day at a local lake. We set up a diving platform with lines running from it in anticipation of people coming and joining us for activities. It took a while. It was getting near time for things to get started, and we were nearly done. We were both nearly OOA, and I sent him in so he could help get the shore activities started. There was only one minor thing to do on the platform (15 feet deep), and I went down to do it while he headed for shore on the surface. I did the job and headed back toward the surface. I stopped suddenly less than two feet from the surface. My tank valve has somehow become entangled in a line while I was on the platform, and the line was stopping me from reaching the surface. I made a couple unsuccessful attempts to get free, and then look a look at my SPG. It read dead empty. I took my gear off, got to the surface, fixed the entanglement, put the gear back on, and headed in with an empty tank. That is the closest I have ever come to becoming a scuba statistic, and it happened two feet from the surface.

 

[2airishuman]

Another instructor and I were setting up for a scuba demo day at a local lake. We set up a diving platform with lines running from it in anticipation of people coming and joining us for activities. It took a while. It was getting near time for things to get started, and we were nearly done. We were both nearly OOA, and I sent him in so he could help get the shore activities started. There was only one minor thing to do on the platform (15 feet deep), and I went down to do it while he headed for shore on the surface. I did the job and headed back toward the surface. I stopped suddenly less than two feet from the surface. My tank valve has somehow become entangled in a line while I was on the platform, and the line was stopping me from reaching the surface. I made a couple unsuccessful attempts to get free, and then look a look at my SPG. It read dead empty. I took my gear off, got to the surface, fixed the entanglement, put the gear back on, and headed in with an empty tank. That is the closest I have ever come to becoming a scuba statistic, and it happened two feet from the surface.

I think that story is insightful and I'm glad you shared it.

My preferred means of avoiding OOA due to simple exhaustion of the primary air supply is to bring lots of air relative to the requirements of the dive. It is not necessary for there to be redundant components to do this although that is certainly one method.

One of the benefits of a slung pony is that readily facilitates abandonment of the primary kit at depth in the event of entanglement.

 

[2airishuman]

So, germane to this discussion is the question: Why NOT dive with redundancy? Here's my list:

• Complacency
• Laziness
• Ignorance
• Arrogance
• Inconvenience
• Too expensive
• Misguided agenda

• Streamlining for better movement through the water
• Keeping an uncluttered kit to facilitate underwater activities such as hunting or photography
  
• Keeping the focus on safety through skills to avoid over-reliance gear
• Maintaining minimal kit size where space and weight are at a premium, as when access to the dive site involves a several mile walk, or where flight logistics complicate bringing a pony bottle

 

[The Chairman]

• Streamlining for better movement through the water
• Keeping an uncluttered kit to facilitate underwater activities such as hunting or photography
• Keeping the focus on safety through skills to avoid over-reliance gear
• Maintaining minimal kit size where space and weight are at a premium, as when access to the dive site involves a several mile walk, or where flight logistics complicate bringing a pony bottle

Like I said: Misguided agendas...

If your stage bottle clutters you up or impedes your swimming unduly, you're probably doing it wrong. IOW, you're avoiding safety gear due to a skills issue. Since I've started using an SPG, I've never ever run out or gas. I still always dive with redundant air. Be it a buddy, a stage or a bail out, it's important to have that redundancy.

 

[Reku]

I think that in ANY situation where you are alone you NEED to have a redundant system (doubles, sm, pony etc.). Not only that but you also need a plan - you can die in 8 feet of water quite easily.

When I dive solo (90% of my dives) I bring 4 lights and 2 of everything else. This includes twice as much back/travel gas and twice as much deco gas needed for the dive. Chances are I won't use the extra gas - so it goes back in the jeep completely full for the next dive but it is nice to have regardless.

Generally I just stash the extra gas near the area I'll be in. It's nice to have a complete set of gases sitting nearby in case of emergency. On top of already diving sidemount and then taking into account the stashed gas - I believe I am sufficiently prepared.

Some people think I'm crazy - and they are right! However it works for me so I'm going to keep on doing it.

*I have had to use the stashed gas before - another diver I found was OOA and I didn't have enough air for both of us to surface (and I had 30mins of deco to do..). We shared air until we got to my stash and then I gave the diver a tank and he surfaced and left it at the front desk for me. I found the diver at about 125' and the stash was at about 110'. I'm not sure how he actually went OOA and I've never seen him since.

 

[letonac]

By the way, H valves do not provide redundancy. It just give you the possibility to have two first stages but juste one tank. That is not a solo diving configuration at all.

In any case, as solo diver, I am using an extra tank, either by using twinset, or sidemount or maybe an AL40 with my single tank (on H valves in France ). No other set up for solo? even shallow, I am not a fan of

 

[Subcooled]

It sucks to run out of air when you are negative (I tried it in a pool) and Murphys law dictates that you run out of air just when you reach the maximum descent speed You cannot inflate a wing or suit then, so better be wearing a jacket BCD with weight pockets, and not a backplate and wing. At what depth would you prefer to experience this?

(ok, experienced divers do not run out of air, but what if you had a single malfunctioning tank, or polluted gas, or you were distracted by pretty fish)

 

[fsardone]

(ok, experienced divers do not run out of air, but what if you had a single malfunctioning tank, or polluted gas, or you were distracted by pretty fish)

Fact is if you are diving solo, you have to have redundancy ... if you want to come out alive from water.
Redundant buoyancy and air source. When I dive solo, I have the dry suit on one of my post and BCD inflator on the other and I dive with separate bottles or closed manifold, switching regs every 10-20 bars.

In addition to that I can ditch abot 20% of my ballast ...

 

[DevonDiver]

I was trying to start a general, abstract discussion, not one about the specifics of my local lakes or my skills.

Why? There's prudent guidance given in solo diver training. Why the need to second-guess that advice? Unless looking for supportive justifications to over-rule that advice because it doesn't fit with what you want to do??

 

[DevonDiver]

It sucks to run out of air when you are negative

How deep was Quero when she perished?

Shallow... negative.... solo.... fatal.