2nds stage vs Octo...

[bug_power]

Okay...I know I need a safe second....however is there a difference between buying another second stage vs buying an octo?

[ObieWan2bWet]

Mostly the only difference in a normal reg and a safe second, 'octo' is the second is detuned so it does not free flow, and the color. Lots of people use normal regulators as seconds, especially ones with dive/predive knobs. If you do use a regular reg as a second that does not have a dive/pre knob, take it to a tech and have them detune it, telling them it is for a second. You may also want to look at inflator hose mounted seconds, they work well and you eliminate a hose from your tree.

[Christof]

I'm kinda confused Obi..... I wasnt aware that my primary "Freeflowed", or at least in my decades old scuba knowledge a free-flowing reg meant it basically leaked, i.e., always had air leaking around the diaphragm.... Could you enlighten me please??
I was going to use a "primary" as my "secondary".....

Christof

[OceanEd]

There are two ways you can create an Octo. Either use a second, second stage; or use an automatic inflator that is also a second stage. Both have advantages and disadvantages.

The ideal second stage Octopus has a longer hose than your primary second stage. This is so that when you are sharing air with someone who is out of air you have more room to manouver and move. If you use a typical primary hose it is shorter and you are in each other's face. The shorter hose will work, but it is harder to move horizontally if you have to swim a distance, and it makes for a very close buddy team if you are making a vertical ascent. It will breathe much better than an automatic inflator that is also an octopus, but you have the hose to contend with. Also, the octopus second stage is generally a bright color that can be seen easily by another diver who might need it and many times it is physically smaller than your primary.

I have never heard of you having to detune any second stage that you use as an octopus. You are receiving the same air at the same air pressure so there is no reason.

An automatic inflator/second stage is great because it eliminates a hose so you have less drag and less clutter. In an emergency you would use it as YOUR primary and the other diver would take your second stage and use it as the octopus. This is because the inflator/octo is on the inflator/deflator hose and it is too short for anything besides going right in your mouth. This also restricts your movements somewhat but you can deal with it. It means that you now have another diver breathing on a fairly short hose (your primary) and that somewhat restricts their movements.

The out of air diver will probably be looking for a brightly colored second stage and there will not be one in the "triangle" on your body where divers are now taught to secure the octopus. Keep this in mind because it means that if the person swimming up to you is out of air and very nervous they will many times go for the air supply they KNOW works and they can see, the one in your mouth. That's OK because that is the one they are going to be using, but if you are not ready for it it can get interesting. You can work with the situation but it is not ideal. Lastly, the air flow coming to most of these units is not comparable to a second stage. You will feel like you are getting less air when you are using it at the same time someone is also breathing from you primary second stage. For this reason you hope you only have to do a straight vertical ascent, and not have to swim any distance horizontally. Some instructors/divers I know that use the inflator/octo put a longer hose on their primary second stage in case they actually have to share air with another diver.

Either system will work for you. Just be aware that practicing sharing air in a pool or lake or ocean during a class is a totally different situation that having to do it for real when you have a very nervous diver at depth who is completely out of air. If you decide to use the inflator/octo (I have used one ever since Scubapro first invented them) then make sure the person you are diving with is aware of the set up and that they are going to be using your primary second stage.

I watched an out of air situation happen that was real, at Hole in the Wall, at 120 feet. Both divers handled it very well and had no problems getting out of the hole and coming to the surface. Of course, they had just finished an Advanced Open Water course and had been trained to do so. Still, it was very interesting to watch and evaluate the entire scenario.

[ObieWan2bWet]

Not to argue with you Ed, but if you do not de-tune a normal second stage, or use the dive/predive switch on "pre-dive", it will have a tendency to freeflow quite easily (if it is tuned properly). The easiest way to test what I am saying, is to hold both second stages, one being an actual safe second (yellow, red, or sold as one) with the mouthpiece facing up and jump into the water, 90% of the time the primary will freeflow, and the second will not. The other is the recommeded pressure differential for octos from the manufacturer is typically a little higher. I am not a tech, and only relaying what I was told by a couple of techs and many tech divers, including my tech instructor. My equip tech detunes my Viper so a slightly higher pressure differential is needed across the diaphram so free flow will not happen as easily, because I use as a second on a rubber lanyard around my neck with mouthpiece facing up and within reach of my mouth without hands, a very common Tech set up. You do not want a reg to begin freeflowing through a squeeze in a cave or zero vis, or on a clip far enough away from your eyes and ears, or in a pocket to freeflow you right out of air, the end result could be pretty bad.

Christof: A freeflow is not a leak from a diaphram or around it, it is the valve opening fully and literally blowing constantly. Air will continue to flow into the reg body until the pressure across the diaphram is increased (turning the reg mouthpiece downward in water or blowing into it) until then air continues to flow unabated. That is basically why I de-tune or slightly increase the pressure differential needed to open the second stages valve, when used as an octo.

[OceanEd]

Obie:

Interesting. I will try it with my class Tuesday night. I agree that the primary 2nd stage usually freeflow's when it is immersed with the mouthpiece up. I have never tried it or noticed with the Octo because all our students and divers have it clipped on to their BC's.

I always thought that the intermediate pressure coming out of the first stage to any low pressure port was the same pressure. I also thought that the dedicated octo. second stages were the same as the primary second stages except for the color and sometimes the size.

If I understand correctly, you are saying that it is the octo 2nd stage itself that has to be "detuned"? Or is it just a normal 2nd stage that is used as an octo?

[ObieWan2bWet]

Obie:

Interesting. I will try it with my class Tuesday night. I agree that the primary 2nd stage usually freeflow's when it is immersed with the mouthpiece up. I have never tried it or noticed with the Octo because all our students and divers have it clipped on to their BC's.

I always thought that the intermediate pressure coming out of the first stage to any low pressure port was the same pressure. I also thought that the dedicated octo. second stages were the same as the primary second stages except for the color and sometimes the size.

If I understand correctly, you are saying that it is the octo 2nd stage itself that has to be "detuned"? Or is it just a normal 2nd stage that is used as an octo?

Ed, I can't tell you if this is industry wide, or simply a caver/techie thing, what I can tell you is the low pressure from the first stage hose to either second has nothing to do with it... sort of... the actual second stage pressure differential required to open the second stage valve is what I am discussing. If you don't detune, or increase that pressure requirement at the second stage, (either a primary used as an octo, or an actual colored octo that should already be set to a higher differential pressure) then they will tend to freeflow very easily, just like a primary does regularly if it is tuned properly. That is why the crews I deal with tweak primary regs when used as "octos" a little to not freeflow as easily, or use the dive/predive switch in the predive position, which does the same thing.

I have a rubber tube that is zip stripped together to form a loop, that we wear around our necks, the mouthpiece of that "octo" is forced through the loop, the purpose is to be able to access the reg without using your hands, you simply bend head down and open your mouth to get to the spare. The problem with that set up is the mouthpiece is always pointed upwards, which tends to create unwanted freeflows at inopportune times if not "de-tuned" a hair. I am not sofisticated enough to tell if the reg is that much harder to breath at depth because of the increased pressure required, I only know it will deliver in an OOA or ascent (I will also occasionaly breath my octo on ascent, otherwise it never gets used). I know a lot of tech guys who still use this method, and it was the way I was taught. (loose DIR fundamentals)

When we cave we actually use our secondary on a long 7' hose wrapped DIR style around and under tank then around neck, for exactly the panic reasons you describe, the primary is left in the predive switched position on the neck lanyard. If OOA situation arises, the primary (actually secondary)... the one your breathing is used as the buddy reg. Because it is 7' long it can be used "in line" single file for a swim exit out of overhead enviro.

That's my story and I'm sticking to it. I'm pretty sure subjecting primary and octos to similar conditions with your students, you will see that the primaries freeflow at a greater percentage than the true octos. :D

Let me know how it works, I have tested it on a limited basis with a few regs here and there with my equip., but never with a classful of multple different regs and octos.

[dagodiver]

I was diving Ginnie yesterday and while on my deco stop I was playing in the "current" and could get my reg's to freeflow with no problem just from the current. I dive the ATX-50 DS4 setups that have the +and- control for "cracking" pressure or as you are calling it a dive and predive control.
I always leave by backup/neck reg in the - position and dont have any problems with the free flow but I can take the one out of my mouth that is on + and can get it to freeflow with no problem. I am not talking about the volume control screw that is another control feature. Hope this helps.
I made it to the "White Room' yesterday.! :cool:



Dago.

[OceanEd]

Mike:

Great description. From what I visualize and from what you said, you have a second stage close around your neck that is always in the position with the mouthpiece up. I
can see how that would be a cause for concern when it comes to freeflowing. When one of our regs freeflows because a student puts it in the water with the mouthpiece up, we simply have them turn it over and it will eliminate the problem. You can't really do that in the situations you describe.

Thats what I love about Spearboard. I am always learning new things and finding out more about different ways to do stuff.

[ObieWan2bWet]

Ed: I am humbled that I can offer a pro like yourself anything useful... thanks.

Dago: That's quite a penetration, 700-800ft... enter at the Ear and through The Lipe, SE down through Keyhole and Cornflakes, and then did you make the jump north to the Expressway Tunnel S to the bottom of the Big Room, or stick to the west tunnel and all that current right to the Bone Room and then to the White Room? Are the Mastadon bones still there? Good it has been dry lately, during rainy season that place can rip a mask off and freeflow a reg IN your mouth in spots.

[kaborkian]

It's pretty much industry-wide that an octopus is "harder" to breath, IE, set for a higher dP than a primary second stage regulator. This is for several reasons, some of which have been mentioned.

One that's been missed I think is the cost/marketing. A "good" second stage that you plan to use all the time is usually setup as easy to breath as possible without leaking or freeflowing while it's in your mouth. It takes precision gear to get this to happen (more $$). Most people don't want to spend the extra cash to get two high $$ regulators, so companies produce a no-frillz cheap version and market it two ways: one with yellow plastic sold as an octopus, and one with black plastic sold as an entry-level primary.

Ed, something you may have noticed and haven't thought of is that you will normally see a leak (not freeflow) from your main way before you ever do from your octo. If your first stage seat is leaking slightly causing higher than design second stage pressure, your lower-set dp primary main will leak slightly, but your octo wont. When this happens, your (well, mine anyway) reaction is to cover all the holes in the main to see if it stops. If you manage to get it to stop, the pressure will build a little more and the octo will begin to leak. Soon as you take a breath or somehow relieve a little pressure, the octo leak stops. This problem is classic with a leaking first stage seat that's sometimes mistaken for a problem with the primary second stage.

For the original question, you should evaluate how you plan to dive and what you need the gear for. Personally, I think there's a much greater chance of me getting tangled up with a loose octo hose than me ever needing to use said octo. The only possible panic situation I can think of where I will need my own octo is when my primary fails stuck closed, which I think is nearly impossible. Therefore, I use an inflator-style octo like this one:

http://www.diverite.com/products/ProductDetails.aspx?productID=RG2200

[dagodiver]

Mike,
I did the bone room and then the white room route, the vis was great and the flow was normal. i had my big tanks all cranked up and we just took a nice slow pace and had a good look around. We played up in the lips bypass area and the top of my tanks show it. On the way out during deco we observed some divers that should not have been in there so we waited and made sure they came out ok and I ended up with about 75 minutes under water. This time of year doing the deco in the open area isnt all bad as there are alot of nice bathing suit bottom's to look at.! :D


Dago.

[ObieWan2bWet]

... If your first stage seat is leaking slightly...

I just had a random moment chuckle reading that... every time I pull out and use my old Sherwood first stage and regs set up... someone inevitably surfaces and says "hey man did you know your tank/first stage is leaking?" I chuckle and say "man that's awsome, I love it when that happens"... and the looks I get when I say that... that was the chuckle part. :D

Anyone who knows the old Sherwood first stages will appreciate that. ;)

[Christof]

Thanks so much guys... Heres a dork question for ya... In my old days of tanking, I simply used my BC for a backup... Only had to once, and I would just inflate slightly, then inhale... Did that from the bottom in 110 ft up, deco'd at around 15 ft for a few minutes, then finished my accent.. My buddy said I was nuts when I even suggested using my Zeagle in that fashion... I guess my question is, why not?? Is the mouthpiece for manual inflation only??

Christof

[ObieWan2bWet]

Mmm... that is an emergency bail out air source, but it is a quite advanced technique. There are quite a few MAJOR issues with that scenario that need to be considered however, which is what makes it an advanced technique.

If you have enough air to power inflate your BC, why would you need to use your BC? Even in an OOA at depth, as you ascend Boyles law takes over and you should be able to get a few puffs from your tank/reg as you ascend, more than likely at least enough for an emergency controlled ascent to get to the surface. Only reason I can think of to use your BC is catastrophic failure of your primary and secondary regs, or first stage, that's by statistic possible, but very unlikely. Second, on ascent your buoyancy control is critical, and if you are not spot on swim up weighted it could be very difficult to maintain neutral buoy and depth adding and relieving air from your BC (without dropping weights). If you are peak buoyed, you probably won't have enough air in your BC to use anyway. Also if you have manually inflated your BC (I do regularly simply to conserve tank air, and I don't need much at depth because I am peak buoyed for my gear set up, normally 1 puff or so is all I need to get neutral at depth) you could have a dangerous CO2 build up and "bad air" so to speak in your BC that if breathed could cause you to black out and drown. Lastly in a panic mode OOA stress situation, heart racing, lungs screaming for air situation it will be very difficult for the average diver to stay calm, and to exhale that last breath, or bubble on ascent knowing they don't have anymore air to breath, the normal reaction is to hold thier breath, which is real bad, and again why it is considered an advanced technique.

I don't recommend even considering it unless you have absolutely no other option, and if you are OOA and peak buoyed it probably won't work anyway.

[Marlinman]

I just had a random moment chuckle reading that... every time I pull out and use my old Sherwood first stage and regs set up... someone inevitably surfaces and says "hey man did you know your tank/first stage is leaking?" I chuckle and say "man that's awsome, I love it when that happens"... and the looks I get when I say that... that was the chuckle part. :D

Anyone who knows the old Sherwood first stages will appreciate that. ;)


I still dive older Sherwoods, and have had that experience waaaaaaaayyy too many times. :lol: