Your Scuba Tank Comes Loose Underwater… Now What?
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Has your tank strap ever worked loose during a dive and allowed the scuba cylinder to move, or even slip completely out of the buoyancy compensator (BC) backpack? If not, you must be doing a good job of cinching the tank strap when mounting the BC. Mounting the BC so the cylinder stays put is a critical part of assembling a scuba unit
New BCs and those that have not been in the water for a while require special attention. When the tank strap gets wet it will likely expand a bit, allowing it to loosen during the dive.
A common solution is soaking the tank strap in water for a few minutes before mounting it on the cylinder. However, since that is not always practical, placing the strap in water for as long as you can, even if it is only a brief dunk, is better than nothing. A wet strap will remain tighter than one that is cinched when dry.
Managing a Slip-Up
If you log enough dives eventually you will be involved with, or at least observe, a cylinder slipping from a BC. It may not be your cylinder that comes loose, but you might be the nearest diver and, therefore, in a position to provide assistance.
At first, a diver won't realize he has a problem, but that will change quickly enough. When he turns his body upright the cylinder will most likely slip through the tank strap and end up dangling by the regulator hoses. He'll certainly take notice when the primary second-stage regulator begins pulling his head back and to the side and the mouthpiece becomes difficult to hold in his mouth.
If this were to happen to you the first thing you should do is grasp the regulator hose just above the primary second stage to keep the weight of the cylinder from pulling the regulator from your mouth. Retaining your air source is top priority.
Because several other hoses extend from the first-stage regulator and fasten to the BC — low-pressure inflator hose, safe-second regulator and submersible pressure gauge (SPG) hose — there is no danger of the tank separating from the diver even if it slips completely out of the tank strap.
The potential for a cylinder to come loose and slip through the tank strap is another reason to use the strap loop that is sewn into the collar of many BCs. During assembly of the scuba unit, the strap is placed over the tank valve before the regulator is mounted. The strap is designed to help the diver mount the BC at the same height on the cylinder every time. However, when the strap is in place it also prevents a slipping cylinder from sliding farther than a few inches.
Typically a diver's buddy or another diver notices that a cylinder is slipping before the diver himself notices. This makes resolving the problem easier — you have help.
Helping Another Diver
If you see that another diver's tank strap is loose or the cylinder is already beginning to slide out, first make contact and calmly inform him of the situation before attempting to help. Climbing on an unsuspecting diver's back without warning could lead to confusion and possible panic.
Signal to the diver to remain calm, establish neutral buoyancy and hover horizontally facedown. This position facilitates getting the cylinder back in place and secured.
With both of you neutrally buoyant, move behind the diver and position yourself over the cylinder. While maintaining contact with the cylinder, loosen the tank strap even more to ensure that the tank will move freely as you push it back into place.
Place two hands on the tank strap and one knee beneath the boot end of the cylinder. Align the cylinder so it is parallel with the BC backpack — often there is a crescent-shaped indentation in the plastic backpack — and perpendicular with the tank strap. Unless the cylinder and strap are property positioned, it is difficult to slide the cylinder into place.
Now in a coordinated effort push the cylinder up with your knee as you pull the strap downward. The strap won't move, but the cylinder should slide through the strap opening. Push the cylinder toward the diver's head until the top of the first-stage regulator is even with the BC collar. This may not be exactly where the diver typically positions it, but under the circumstances it will suffice.
With the tank strap in the desired position, move higher and straddle the cylinder. Placing a knee on each side will help you maintain your position while cinching the strap.
Before closing the buckle the tank strap must be tightened securely or the cylinder will work loose again. The exact procedure used to tighten the strap varies depending on the type of buckle. The black plastic buckle with slots through which the tank strap is threaded is most common.
To tighten the strap, begin by removing it from the end of the buckle. (You may have already done this when loosening the strap before attempting to reposition the cylinder.)
With the buckle open, grasp the free end of the strap and pull hard, as you do when assembling the scuba unit. Once the strap is as tight as you can pull it, partially close the buckle to retain the tension. Hold the buckle partially closed while you re-thread the free end of the strap back through the end slot. Without releasing the tension, snap the buckle closed and secure the end of the strap.
As a final test, place one knee beneath the boot end of the cylinder, both hands on the tank strap and attempt to move the cylinder inside the strap. The cylinder should not budge; if it does you need to open the buckle and tighten even more.
The most common problem divers face when repositioning and tightening another diver's cylinder is sliding it back through the tank strap. To keep the two from binding, the strap must be sufficiently loosened and the cylinder and strap exactly perpendicular.
The other common problem involves buoyancy. Both divers must establish and maintain neutral buoyancy throughout the process, unless the diver with the loose cylinder is on the bottom or holding onto a secure object.
Going It Alone
The easiest and safest way to resolve a slipping cylinder is with the help of another diver. And unless you are diving solo — a specialty certification that teaches students how to safely dive without a buddy — your buddy should always be nearby. But if he or she isn't and you discover your scuba cylinder slipping from the tank strap, you may have to resolve the issue yourself.
First and foremost, remain calm; there is no need for panic. As mentioned earlier, the cylinder will not completely separate from your BC. So as long as you keep the regulator in your mouth you will have a source of air.
Begin by addressing buoyancy. If near the bottom gently settle onto it and vent air from your BC. This will help you to stay put while securing your cylinder. If you are mid-water and the bottom or a stable surface is beyond your profile, establish neutral buoyancy.
Carefully remove your scuba unit and use the same technique described earlier for helping another diver reposition the cylinder and secure the tank strap.
After removing the BC make certain that it, without you wearing it, is neutrally buoyant. Weight-integrated BCs tend to be negatively buoyant when removed underwater. The BC sinking and you floating upward at the same time would make securing the cylinder a difficult task.
Once you're finished repositioning the cylinder and tightening the tank strap be sure to perform the final test described earlier; place one knee beneath the boot end of the cylinder and both hands on the tank strap; now attempt to move the cylinder inside the strap. Neither should budge.
It is not every dive that a scuba cylinder slides out of the tank strap, but it does happen, so it pays to know how to handle it. If you or someone with whom you are diving experiences a slipping cylinder, simply remain calm and resolve the situation as demonstrated here.
As a dive instructor I teach two things that can help alleviate this situation. First, when assembling gear, the diver should tighten the tank straps and then grasp the cam buckle and try to wiggle it up and down. If it moves at all, when the webbing stretches, the tank will be loose enough to slip. Second, once the diver is in the water and either doing an in-water predive safety check (shore dives) or an in-water check that nothing moved during entry, their buddy should do the same "wiggle" test (now with wet straps) to check. As prudent divers, we all know something found at the surface is usually a lot easier to fix than something found at 60 feet...