Spare air/pony bottle---should I get one?

[JohnN]

Please explain, any first stage I know will deliver down to 0 psi tank pressure relative to the regs surrounding pressure.

My take on A SpareAir is that it better to do a CSEA with one than without. If he takes it on every dive because it is easy and unobtrusive, that is much better than a larger cylinder that is left behind because it is a pita to deal with.



Bob

My understanding is that balanced 1st will stop delivering air when the IP is reached. Even if you're correct, that 150 psi represents (150/3000)*3 is a whopping 0.15 ft^3

Its a free world out there and most anyone can aspire to receivea Darwin award. I wouldn't want to try a CSEA from 100', For me, a Spare Air doesn't increase my odds when poo hits the fan, and I don't have a regular dive buddy I would trust my life with

 

[doctormike]

SDI does accept a H-valve as redundant airsource. Here are even self reliant divers who were using a single tank and H valve as redundant airsource (during the course while solo diving at 80 feet depth). One single failure (tank neck) can lose a divers gas.

23.8 - 2

https://www.tdisdi.com/wp-content/uploads/files/sandp/currentYear/SDI/part 3/pdf/individual/SDI Specialty Standards_23_Solo_Diver.pdf

Yeah, I wondered about that H-valve thing. I guess it's a legacy of some sorts. Maybe they figure that catastrophic gas loss is almost always from free flow 2nd stage, burst LP hose, or less commonly a first stage failure. The H-valve deals with all of those, it only is inadequate if you have a tank neck (burst disk or o-ring) failure. And I guess SDI crunched the numbers and figured that something like that was such an extremely remote possibility that they decided to give a pass to the few people who wanted to do the class with an H-valve.

 

[AdivingBel]

I'm a photographer ergo, I dive with redundancy. It is foolish not to.

I was referring to the probability of both a catastrophic gas loss and losing even an insta-buddy in a high viz environment on the same dive.

If you choose to not dive as a buddy-pair (due to photography or any other reason), you should absolutely sling a pony. Saying it's foolish to not sling a pony when diving with a buddy especially in the environment specified by the op (warm water, high viz) is your opinion, but it's not borne out by reality (if that's what you're saying).

 

[redacted]

My understanding is that balanced 1st will stop delivering air when the IP is reached. Even if you're correct, that 150 psi represents (150/3000)*3 is a whopping 0.15 ft^3

Its a free world out there and most anyone can aspire to receivea Darwin award. I wouldn't want to try a CSEA from 100', For me, a Spare Air doesn't increase my odds when poo hits the fan, and I don't have a regular dive buddy I would trust my life with

Your understanding is incorrect. When tank pressure falls below IP, the 1st stage valve simply stays open.

A properly sized pony will provide more reserve that a spare air. Both are better than nothing.

 

[scubadada]

...A properly sized pony will provide more reserve that a spare air. Both are better than nothing.

This topic has been discussed many times. In Florida, I generally dive solo, I take the topic reasonably seriously, though I have never had an equipment malfunction resulting in air loss. Divers should make their own calculations covering the dives they do. I use twice my average RMV in my calculations, maybe a bit high, but on the safe side.

So, with a 3 cf Spare Air, I could make a normal direct ascent to the surface from 60 ft, not bad. From 100 feet, I'd have to hustle at a little over 60 ft/min to make a direct ascent to the surface, not terrible, better than nothing. From 130 feet, I'd have to ascend at nearly 100 ft/min to make my direct ascent, that's really fast, but better than drowning.

On the other hand, with my 19 cf pony, from 130 ft, I can spend a minute at the bottom, make a normal ascent, and have a 3 min safety stop.

 

[KeithG]

Thanks for the quick and thorough replies. I looked at several previous posts on the subject but I probably should have given more detail. Most of not all of dives will be warm water high vis dives so my main concern is similar to one of the replies...having my buddy wander off on me.

IMHO, Not needed for (my understanding of) your type / level of diving. It is an equipment solution to a very simple skills problem. This is the basic forum, not advanced. You appear to be doing warm water high viz group dives with a DM.

This discussion ties into a few threads I started after our last vacation trip: one was about becoming an equipment christmas tree, the other was about club trip divers diving as a group and not buddy pairs.

The equipment thead raised the concept of minimal vs minimum gear: lots of peoples MINIMUM gear list means they are taking stuff they do not need (me included).The club trip thread revealed that lots of people feel it is okay to dive as a group without a distinct buddy.

But you need to make your own decision based upon your dives.

Some other things to think of:
- exactly what are you going to do when your dive buddy wanders off? how would redundant gas supply help?
- what were you doing that allowed your dive buddy to wander off? a buddy team failure means both people failed.

 

[JohnN]

Your understanding is incorrect. When tank pressure falls below IP, the 1st stage valve simply stays open.

Thanks, appreciate the education

 

[BRT]

This topic has been discussed many times. In Florida, I generally dive solo, I take the topic reasonably seriously, though I have never had an equipment malfunction resulting in air loss. Divers should make their own calculations covering the dives they do. I use twice my average RMV in my calculations, maybe a bit high, but on the safe side.

So, with a 3 cf Spare Air, I could make a normal direct ascent to the surface from 60 ft, not bad. From 100 feet, I'd have to hustle at a little over 60 ft/min to make a direct ascent to the surface, not terrible, better than nothing. From 130 feet, I'd have to ascend at nearly 100 ft/min to make my direct ascent, that's really fast, but better than drowning.

On the other hand, with my 19 cf pony, from 130 ft, I can spend a minute at the bottom, make a normal ascent, and have a 3 min safety stop.

I hope you use a bigger tank than an AL80.

 

[uncfnp]

@AdivingBel
I apologize if I came across too strong in my defense of redundancy. It was not my intent to imply divers needed ponies or such but to provide a safe place to explore options and necessary info to do so if he/she so chooses. There is a history on SB that ponies are a "gear solution to a skills problem" so I get a bit defensive or mother henish if I think this is happening to the poster. My own choice is not to carry a pony on most warm water, low risk dives that are not true solo. Even then I don't carry on relative shallow, low risk dives.

I have had three acquaintances, two online and a third IRL, pass while buddy or group diving. My own early experiences with my partner is in part what lead me to explore solo training. While overly attentive at times, whenever I truely needed his attention it was impossible to get. I tried tank bangers and other noise makers all to no avail. And a moments inattention by the buddy is all it takes (Have you ever had an OOA and tried to breathe from a near empty tank? I have, twice). So even diving together I learned to be very self reliant very early own and I have encouraged the same in him. Now even when we dive together we both expect to be able to deal with situations on our own. So I find I tend to encourage this self reliance in others that are not doing true team/buddy unit diving.

As for instabuddies, I really have little opinion since as said I only have the one experience and it was positive enough that I started a thread about my good instabuddy dive.

 

[scubadada]

I hope you use a bigger tank than an AL80.

For what, exactly? How is this related to my post on redundant gas supply?