Should I buy a pony bottle?

[dumpsterDiver]

We've not heard back from Boulderjohn?????.

In my experience his comment was not correct (except maybe for the honking scuba Pro reg that was discointinued 30 years ago)???

Haven't any of "you people" ever breathed down a tank? If it is done with a digital pressure guage it is quite obvious that you can continue to breath for a long time; even as the pressure approaches zero.

When I was an instructor this was a REQUIRED portion of the course for every student. They must know what it feels like when the tank approaches "E" so they don't freak out.

To say that it is impossible to utilize the last 3 cu-ft of an 80 cu-ft tank is a significant mistake in my opinion.

A diver can do a lot with 3 cu-ft on an ascent and for a diver to assume that there will be no air when the pressure reaches 140 over ambient could make them do something stupid on an ascent.

Maybe there are some other regs that will not deliver air, but i've never found one. Being able to milk the last 10 -15 breaths from a low tank could be the difference between life or death in a critical situation.

 

[mathauck0814]

We've not heard back from Boulderjohn?????.

In my experience his comment was not correct (except maybe for the honking scuba Pro reg that was discointinued 30 years ago)???

Haven't any of "you people" ever breathed down a tank? If it is done with a digital pressure guage it is quite obvious that you can continue to breath for a long time; even as the pressure approaches zero.

When I was an instructor this was a REQUIRED portion of the course for every student. They must know what it feels like when the tank approaches "E" so they don't freak out.

To say that it is impossible to utilize the last 3 cu-ft of an 80 cu-ft tank is a significant mistake in my opinion.

A diver can do a lot with 3 cu-ft on an ascent and for a diver to assume that there will be no air when the pressure reaches 140 over ambient could make them do something stupid on an ascent.

Maybe there are some other regs that will not deliver air, but i've never found one. Being able to milk the last 10 -15 breaths from a low tank could be the difference between life or death in a critical situation.

Last summer we took our AL40 stages and went into a river behind a country club in New England to pick some golf balls off the bottom (~6-7 feet). We're talking no BC, just a plate with a 40 slung. Down for a few minutes, back up; rinse - repeat, etc.

Anyway - I sucked that tank dry (I mean - bone dry). When I took the reg off and opened the valve not a single sound. I reject the notion that you would require more than the IP to be present to get a breath.

That said - I was darn nearly snorkeling without the tube, so I suspect if you were to breathe a tank "dry" at depth, you'd have some air when you got to the surface just due to pressure release and gas expansion.

 

[dumpsterDiver]

Last summer we took our AL40 stages and went into a river behind a country club in New England to pick some golf balls off the bottom (~6-7 feet). We're talking no BC, just a plate with a 40 slung. Down for a few minutes, back up; rinse - repeat, etc.

Anyway - I sucked that tank dry (I mean - bone dry). When I took the reg off and opened the valve not a single sound. I reject the notion that you would require more than the IP to be present to get a breath.

That said - I was darn nearly snorkeling without the tube, so I suspect if you were to breathe a tank "dry" at depth, you'd have some air when you got to the surface just due to pressure release and gas expansion.

Funny you should say that. I worked for years as a golf ball diver, often in water that was too dirty to read a pressure gage. I would know I was getting low on air by the increased resistance and I often breathed a tank down to zero before getting out (of course I was just 6-10 feet deep)... but still; I've done it literally hundreds of times and to read that it is impossible on here is surprising.

 

[idive2]

That a reg will not deliver any air below 140 psi above ambient pressure?

Anyone else know anything about this?

It is really a very important consideration if the last 3% of your air supply is completely unusable?

Anyone have a reference for this information?

I ran a tank down once and the pressure on the gauge was around 200 psi when I took my last breath
from the reg. The reason I was aware of the gauge reading it was a safety stop that I felt I had to make and was watching
the gauge very closely. I remember reading this stuff about the reg not being able to deliver air all the way down to zero
and still wonder if that was what I was dealing with. When I did disconnect the reg and check the tank there was just a bit
of pressure but it did not seem like 200 psi but kinda hard to tell.

 

[Mantra]

Make sure you go through all the posts in that thread and read all of Rich Murchison's posts (Hint: now I know the answer(s))

if you visit the thread, his excellent info is indeed impossible to miss. My understanding was that the exact time would still be an 'it depends' based on physical characteristics, relative surface/depth flow rates notwithstanding. Great thread though, isn't it! Lots of sophisticated stuff there.

 

[mathauck0814]

I ran a tank down once and the pressure on the gauge was around 200 psi when I took my last breath
from the reg. The reason I was aware of the gauge reading it was a safety stop that I felt I had to make and was watching
the gauge very closely. I remember reading this stuff about the reg not being able to deliver air all the way down to zero
and still wonder if that was what I was dealing with. When I did disconnect the reg and check the tank there was just a bit
of pressure but it did not seem like 200 psi but kinda hard to tell.

You were likely at (or nearly at) 0. SPG are most accurate in the middle of their range. <1000psi I don't really trust it to be exact. But you should be out of the water by then in a lot of cases anyway.

 

[dumpsterDiver]

I ran a tank down once and the pressure on the gauge was around 200 psi when I took my last breath
from the reg. The reason I was aware of the gauge reading it was a safety stop that I felt I had to make and was watching
the gauge very closely. I remember reading this stuff about the reg not being able to deliver air all the way down to zero
and still wonder if that was what I was dealing with. When I did disconnect the reg and check the tank there was just a bit
of pressure but it did not seem like 200 psi but kinda hard to tell.

Almost for sure, your guage was off (by about 200 psi). 100 psi is a lot of pressure, think of how hard a bike tire is with that amount of pressure in it.

 

[Hawkwood]

if you visit the thread, his excellent info is indeed impossible to miss. My understanding was that the exact time would still be an 'it depends' based on physical characteristics, relative surface/depth flow rates notwithstanding. Great thread though, isn't it! Lots of sophisticated stuff there.

Mantra, that's why I qualified with "answer(s)". Thanks for pointing me to that thread by the way.

 

[ianr33]

Best source of emergency air is a good buddy. Failing that a small pony (13 or 19) seems a reasonable choice when travelling. First stage failure may be rare, but blocked filters from debris in the tank are not unheard of. (Ask Dr Bill about that)

If you do decide on a pony sling it. (Ask Dandy Don why mounting it on your main tank is a bad idea)

Slinging a second 80 works great for extended dives, but I can't see the average Caribbean dive op allowing that! Similarly with H/Y valves,they only work if you switch the valve first.

 

[Hatul]

Best source of emergency air is a good buddy. Failing that a small pony (13 or 19) seems a reasonable choice when travelling. First stage failure may be rare, but blocked filters from debris in the tank are not unheard of. (Ask Dr Bill about that)

If you do decide on a pony sling it. (Ask Dandy Don why mounting it on your main tank is a bad idea)

Slinging a second 80 works great for extended dives, but I can't see the average Caribbean dive op allowing that! Similarly with H/Y valves,they only work if you switch the valve first.

I would flip that around. The pony makes a better source of emergency air than your buddy. First it's much easier than sharing air and making an ascent together, and it does not affect my buddy's air supply. A good buddy is better than a pony for diving emergencies, but just for the extra air the pony is at least as good.