Technical Diving Equipment
Deco and Stage Bottle Rigging
Decompression bottles store the gasses used on the ascent from a dive. They should be made of aluminum (instead of steel) since these types of tanks swing from slightly negative to slightly positive as their contents is consumed and so they don't adversely affect the diver's trim. Typical sizes are 30 Ft3 and 40Ft3.
Stage bottles are used to provide additional gas on dives where the back-mounted tanks alone cannot carry a sufficient quantity by themselves. Like deco bottles, stage bottles should be aluminum (instead of steel) for their superior buoyancy characteristics. The most commonly used size is 80 Ft3.
Both type of bottles, deco and stage, are clipped to the divers left side only. The bottles are clipped to the left shoulder and left hip D-ring. The right hip has no D-ring since this is where the light canister is mounted on the waist strap. The goal in rigging these bottles is to keep the top of the bottle in close to the diver to minimize drag, and to keep the bottom of the bottle fairly free to swing into the slipstream such that water can flow longitudinally along the length of the bottle. This has the benefit of minimizing the frontal area the bottle presents to the flowing water as the diver swims, thereby minimizing drag. The points of attachment on the bottles should be snap-bolt clips and rope. Never use suicide clips or any metal-to-metal connections. Suicide clips will entrap line when you least expect and have killed many divers over the years. Metal-to-metal connections have also killed many divers who became trapped and were unable to cut themselves free. This is why you should attach your clips to the bottles only with rope that can be cut free if necessary.
Additionally, deco and stage bottles should be permanently marked with the Maximum Operating Depth (MOD) of the gas they're intended to contain. The single largest cause of death among technical divers today is breathing the wrong gas. This happens when a diver gets confused and inadvertently opens the wrong valve or grabs the wrong regulator. If you can find a way to reduce the chance of this happening to you, you'll have drastically improved your odds The best way to do this is to mark your bottles with the MOD in big, bold lettering. Three inch high numbers are the way to go. Such clear markings permit you to positively identify the bottle you intend to breathe, and more importantly, permit your buddy to see which bottle you're attempting to breathe. With two people independently identifying the bottles at each gas switch, the chances of making a mistake (one that's missed by two people) is drastically reduced.
To deploy the stage/deco gas, you first identify the bottle and open only that valve. All other valves should be kept closed unless you're breathing from them. If only the valve attached to the bottle with the correct MOD is opened, only the correct regulator will deliver gas. Even if the other regulators were pressurized to keep water out, they will only deliver a fraction of a breath before stopping; only the correct regulator attached to the intended gas will deliver. Once you've done the gas switch and you and your buddy have double-checked that you're on the right gas, you shut down the stage/deco valve you were breathing before.
You can mark the oxygen fraction on a sticker near the neck if you like, but keep in mind that the FO2 is almost meaningless underwater. You don't want to be looking at a sticker with "31%" written on it than have to do a bunch of mental arithmetic to figure out if at your current depth that gas will kill you or not. With the MOD in big, bold lettering on each tank, all you have to do is check how deep you are to know if you can breath from a cylinder.
Below are some pictures of the best way to rig your decompression and stage bottles.
How to rig your stage/deco bottles.
Regulator Configuration For Doubles
This is how we configure our regs on a set of doubles:
Right post (as you wear them):
Left post (as you wear them):
The one thing that decides where the rest must go is the longhose.
When we share gas we donate our longhose. The hose is a longhose because we have to be able to share gas with the reciever swimming in front and the donator behind him. If we do this for instance in a cave or other tight spot we have the possibility of rolling our valves against the roof of the cave. In this case the left post will roll off and the gas will be shut off but the right post will only roll on so it will stay on. Because the right post can't roll off and create more problems in a serious situation we have the long hose on our right post.
Since the long hose is on the right post we need to have our backup reg, which hangs in a bungee cord around our neck on the left post. Otherwise we would not have any redundancy which is the purpose of two regs and a double tank in the first place. Read more about when to use doubles and single tanks here .
The wing goes on the right post because of similar reasons why we put the longhose there. If we pass a tight spot and roll off the post with the wing inflator we don't want to find this out by sinking into the silt unable to inflate. This should however not really happen since standard procedure is to always check your valves when there is a possibility that the valves have touched the ceiling. Another reason, which is my favorite, is when you dive in cold water and your inflator mechanism freezes in the open position you can just dump your gas with your left hand while shutting down the post with your right. It's very effective and I've seen this done for real on several occations.
Since we have our wing on the right post we put our drysuit on the left, unless we are using a separate drysuit bottle. Actually using a separate bottle is neccessary when having a helium based breathing gas in your doubles and personally I prefer to use a drysuit bottle all the time. Then I can also use argon which is better due to it's lower thermal conductivity.
The last thing is the pressure gauge which we put on the left post. The reason for that is simply because it's easier to have it there as it wont be in the way of the longhose when we have to donate that. Another reason is when you are scootering you are using your right hand to scooter so you can unlip your pressure gauge and look at it without stopping or slowing down.
As you can see in the pictures I use Apeks DS4 first stages which are good reliable regs. Apeks together with Scubapro is probably what you see most tech DIR guys use.
I angle the DS4s to take the strain off the HP hose going to your pressure gauge and the longhose. How much angle needed depends on your tanks and valves. In the pictures they are rigged on a set of double 12 liter tanks which are small doubles compared to a set of double 18s or PST 104s.
Also notice on the right post that I use the back LP port to run the longhose. That gives the longhose a natural tendency to stay behind the wing. On some wings, like the circular Evolve from Halcyon, you might have to route the longhose OVER the wing instead of behind it - if you do use the other port. The reason one might have to go over the wing instead of behind it is because the longhose won't stay behind the wing which actually depends on how far your light canister extends down.
The backup reg needs to long enough so you can look to your left in the water. That is usually around 24" but depends on what first stages you have and how big/small your are. A custom hose length may be neccessary. If the hose is too long it will drop down over you right arm and usually be in the way of your right chest d-ring.
The wing inflator hose needs to go from the right post straight to the corrugated hose and run on the side closest to you. A 24" hose here is also usually fine.
The drysuit hose is run from the first stage down, under your left armpit, under the harness and to the inlet valve. Too short is a pain in the ass. The hose that comes with the drysuit is usually fine. Think it is a 36" hose but try with the one you have and see if it fits. If you use an argon bottle you need a shorter hose.
The HP hose for the pressure gauge needs to be long enough so you can operate it easily. Usually 24" is perfect but sometimes you may need slightly longer or shorter. Many people have tendency to use a too short hose here in their excitment to make everything is slick as possible so be aware of that. I use a 25" hose.
When measuring hoses most people don't know how to do that. Staying consistant with what is used in the hydraulic and pneumatic industry means that you measure from sealing surface to sealing surface on the assembled hose. So the threads are not measured on the barb and the length of the hose is longer than what the manufacturer cuts the hose itself when they assemble it.
But this doesn't matter much as the hoses from different sources have different lengths even if they are supposedly the same. Also length differences between different batches from the same manufacturer can occur. If you mail order make sure you can return the hose if it's really wrong. I usually buy mine in the dive shop so I can try it myself. Same thing with boltsnaps. Some are good and some are really bad but if you can try them first you can just get the good ones and leave the rest to everybody else.
This how we configure our regs on the doubles. Everybody is expected to have it the same way and with the proper hose lengths.
Most common mistakes for those preparing to take tech or cave training is using a too long hose for the backup and a too long HP hose unless they know it suppose to be shorter.
Why a backup reg?
Normally we breath from our primary regulator, our longhose. During decompression we use one of our deco bottles and when diving stage bottles we breath from them. When the longhose is not used it is always clipped of with an attached boltsnap to our right chest D-ring.
If we have a problem we donate the only regulator we KNOW is working - the one we are breathing. That way we also know that we give away something that is safe to breath at that depth - important when you use multiple gases.
After donating our regulator we need something else to breath - our backup regulator. Since our backup is what we are going to use in an emergency we need to find it fast and we need to be sure that it is going to be there. Let's see how we can do that.
The backup second stage hangs around our neck like a necklace. The necklace is made of elastic bungee, aka shock cord or surgical tubing. Surgical tubing is smoother but will deteriorate and dry rot after a couple of years. Bungee however will hold for many years and can be found in most hardware stores or marine stores. If you want it in black you may have to lock around though.
Make the loop the length that you can just reach the regulator with your mouth while wearing it. That way it's going hang quite close to you but not so close that you can't look down while diving.
The cord or surgical tubing is put under the same tie wrap as the mouthpiece on the second stage. If you use bungee then make a knot when you have adjusted it so it can't be pulled through. With surgical tubing that is not necessary.
Let's say you get something wrapped around your backup regulator and you keep swimming without noticing. If your backup reg was not securly attached it would be pulled out and if you needed it it would not hang around your neck anymore.
Some people use a loop that is put around the mouthpiece. As you can understand from above that is not a good idea. I actually used to have it rigged like that when I started tech diving because that was how I was taught. After having had the backup coming undone twice so that I could not find it when I needed it I stopped using the loop.
Picking a suitable second stage
Since the backup will hang upside down it will be prone to freeflow. Actually most second stages are suppose to be adjusted when serviced so that they freeflow in this position. To solve that problem you have three options:
Option number three is what I prefer. Now I can detune the second stage underwater and if I need to breath it for an extended amount of time I can tune it up again.
In the pictures above the cracking pressure adjustment is the metal knob to the left (Apeks TX50). The following second stages currently in production (2006) have this adjustment; Apeks TX50/100/200, Apeks ATX50/100/200, Apeks XTX50/100/200, Scubapro G250, Scubapro S600.
Apeks and some other manufacturers put hose protectors near the second stage. Cut them off as they will only stop the hose from doing a nice soft bend. When you decide on the proper length for the bungee don't forget that wearing a hood will make it shorter.
If you like something fun to do, you can practice getting the backup reg in your mouth without using your hands :)
With this setup we know where our backup is and we are going to be 100% sure that it is going to be there when we need it. What more can we possible ask for?
Single tank, H-valves or doubles?
When we do recreational no decompression diving a single tank is the weapon of choice. For anything deeper than 100ft / 30m or anything involving decompression or an ovearhead environment like wreck penetration, caves or similar the doubles are the right choice.
The reason is simple. If we do a dive in the ocean and we experience a malfunction with our equipment and can't breath we can signal our buddy and share gas with him. Obviously we want to terminate the dive but what if he also has problem now? Well, we could both do a swimming ascent straight to the surface. That gives us the ability to handle two severe problems without getting into real trouble.
When we venture into an overhead environment or we have mandatory decompression to complete we have to stay down and our option to go to the surface has been removed. Now we don't have any way to survive two severe equipment problems. So we need to carry more equipment - what we call redundant equipment. A set of doubles has two connected but independent regulators consisting of one first stage and one second stage each. If one fails we switch to the other. If that one fails too we start sharing gas with our buddy.
Why not just a H-valve and two first stages on a single tank?
That may seem like a good solution but it's not really for a couple of reasons.
Deeper dives, decompression and overhead are complex dives and since we don't have the option of going to the surface we need to handle the problem under water. To be able to do that we need to carry more gas then we intend to use - reserve gas. If we are deeper 5 minutes worth of gas is a whole lot more than it would be shallow. So these dives require a bigger safety margin and a single tank is simply not big enough to carry an adequate amount of reserve gas.
Another drawback to using two first stages on a single tank is complexity. You need to be as familiar with your configuration as a double tank diver but also you need to be able to reach back and operate your valves because if you can't shut it down you have gained nothing. H-valves and Y-valves are often difficult to reach and the configuration is not streamlined and neat because you have to much regulator and not enough room.
Another reason why some want to use an H-valve is so that they can use the same setup for their doubles. Besides the very busy configuration you also get the wrong hose lengths because these have to fit you doubles where the first stages are located on each tank and not in the middle. So while it might work it is not optimal.
What to do instead?
Well, I suggest getting a dedicated first stage for single tank diving with the right hose lengths. It's not a major investment and if don't use it often you could skimp on getting second stages and just move those between you double regs and your single reg. You also have the advantage of being able to use any tank on your vacation since you have it setup already. And most important you don't have to deal with the unnecessary complexity of having two first stages that is of no gain because any dive requiring two first stages also requires the added gas of a set of doubles.
So in summary use a single tank with one first stage for dives down to 100ft / 30m not requiring any decompression and not venturing into any kind of overhead. Use a set of double tanks for the rest and skip the H-valves all together.
Gas Switching Procedure
Breathing the wrong gas at the wrong depth will kill you.
This is a simple procedure yet it can cause big problems for those trying to do it fast and mess it up. Remember, slow and deliberate is always fast. Also keep in mind that all deco and stage bottles are turned off when not in use. That prevents us from loosing gas without knowing it and is also an additional safety step preventing us from breathing the wrong gas.
These are the most common mistakes for those relatively new to this:
Switch to stage or deco bottle
1. Wait until you reach the switching depth.
2. Hang up you primary light (turned on, pointing down).
3. Choose the proper bottle by looking at the MOD label and show it to your buddy who verifies it with an OK (depth and gas is correct).
4. Grab the second stage with your right hand and route the hose around your neck.
5. Open the valve and purge the second stage.
6. Remove the longhose (with left hand) and put the stage/deco reg in your mouth and breath.
7. Clip of the longhose on the right chest D-ring.
8. Unclip your light and signal you buddy that you are ready with an OK.
Switch back to the longhose.
1. Hang up you primary light (turned on, pointing down).
2. Unclip the longhose and hold it in your right hand.
3. Remove the reg from your mouth with your left and pull the hose over your head.
4. Put the longhose in your mouth and start breathing.
5. Close the valve on the bottle you where breathing.
6. Lift the innertube with your left hand (thumb) and push the hose in there.
7. Pull on the hose and make sure the second stage is secure under the innertube.
8. Unclip your light.
Switching between multiple bottles
If you need to switch from one stage to another, from a deco bottle to another or any combination, you go to the long hose first. Like this:
1. Switch back to the longhose and stow the bottle you are breathing.
2. Move bottles around if it makes things smoother.
And you can have the light clipped off until you have completed the whole process.
If you are switching deco gases, let's say from 50% to Oxygen, you switch to backgas (longhose) at 9m/30ft for the last couple of minutes. That gives you time to stow the 50% and move things around. Then ascend to 6m/20ft and deploy the oxygen. This is the cleanest and safest way to do it.
When doing more than 20 minutes on oxygen you have to do a gas break to keep the gas exchange effective. When you go to breath the longhose you can stow the reg on the oxygen bottle just by clipping the second stage to one of the boltsnaps or the handle. Anyway you chose to stow it, you NEVER let regs hang around your neck. Why? Because when something happens you will not know what you are breathing or even if it is turned on.
When you switch deco gases it's best to do it one at a time, especially if you're not very experienced. The chance of something going wrong is always bigger at the gas switches so it's a good idea to supervise each other. I have stopped people from breathing oxygen at the wrong depth or choosen the wrong bottle several times. Also it's easy to get something into the second stage, like small sticks, sand, clay and if you breath that you may need some help to recover. That's by the way why you need to purge the second stage before breathing it. But we all make mistakes, right?
When you are using stages in the ocean you often suck them dry or almost dry. Then you switch to the backgas (unless you have several stages which is uncommon). If you want to you can signal you buddies, show them the switch sign and everybody can do the switch. Nice if you have similar gas consumption since everybodies stages should be getting close to empty. If you are experienced you can switch on the fly though.
Last Modified On:
Life's a beach...then you dive !!!