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BCD and Single Tank Systems

  • $999
    Agir Brokk Single Tank Package
  • $1821.35
    TECLINE Single Tank Complete Package
  • $869
    xDeep NX Zen Deluxe BCD
  • $549
    Agir Brokk Blackbird 28lb Donut Wing
  • $869
    TECLINE Peanut 21 Single Tank System
  • $45
    TECLINE 2kg | 5lb Trim Pockets (pair)
  • $469
    xDeep Xeos 28lb Wing
  • $469
    xDeep Xeos 38lb Wing
  • Special Price$599
    xDeep Ghost BCD
  • $135
    xDeep Dumpable Weight Pockets (pair)
  • $469
    TECLINE Peanut 21 Single Tank 46lb Wing
  • $829
    TECLINE Peanut 21 Ultralight Single Tank System
  • $469
    TECLINE Donut Single Tank Wing

GEAR GUIDE

Should I use a backplate and wing or BCD? 

Reliability, durability, and modularity guarantee the backplate and wing (BPW) will always be superior to BCD designs. The BPW is simple: a length of webbing threaded through a pressed metal plate and attached to a protected bladder. We recommend a BPW for all backmounted diving, which includes a standard single tank recreational setup.  

If any component wears out or is damaged, you can just replace that component.  You can also swap only those components you need to change between different equipment configurations (e.g. the same backplate and harness can used for both recreational and technical/CCR dives by replacing only the wing).

For more information about choosing a BPW, see the Gear Guide for our Buoyancy-Control category. For information about choosing a BCD keep reading this page.

HOW TO GET GOOD TRIM WITH A BCD

Most divers are taught in their Open Water course to mount the cylinder so that the cam band is just below the neck curve (where the cylinder walls begin curving into the neck).  This configuration does not take account of the physical characteristics of a scuba cylinder and forces a diver into an inefficient head-up fins-down position which tends to damage the reef, stir up silt, and waste both energy and air.  In short this common error causes environmental damage and shorter dives.

You can achieve good trim with a BCD by understanding the balance point of a scuba cylinder. The horizontal balance point of a scuba tank is about one third of the distance between the start of the neck curve and the centre point (from base to top of valve). This is where you should put your single cam band, or top cam band for dual band systems, to attach your BCD.

The cylinder walls are the thinnest part of the tank. The base is a concentration of mass, more so for aluminum cylinders where the base is thicker than the walls.  The cylinder neck is another concentration of mass and has the thickest walls, plus weight of the valve and first stage regulator.

For more information about good trim and how it is important, see the Gear Guide for our Buoyancy-Control category.

HOW TO CHOOSE A BUOYANCY CONTROL DEVICE (BCD)

Our advice: compartment or wing jacket with integrated weights and no integrated regulator. 

Air Bladder: What are the different types of BCD?

There are three main configurations for a jacket style BCD based on they style of air bladder: (1) basic jacket, (2) compartment jacket, (3) wing jacket

The cheaper, basic jacket BCDs use a single compartment, formed by two airtight layers, inside and outside, that are sealed around the edges. There will be a single air bubble siting at whatever point is highest on the BCD. If you roll to your side, you will feel the bubble roll around within the BCD to stay at that highest point. Most rental gear will use this system, however if you are buying gear it is probably better to invest in something more comfortable.

Compartment jacket BCDs are designed with internal compartments, so that each point within the jacket has a limited range of expansion. This causes the air to be more evenly distributed around the BCD, to avoid the single air bubble effect. Air movement within the BCD is slowed as air moves and equalises between multiple compartments, making for smoother transitions as you move around in the water. Compartment jacket BCDs are much more comfortable to use.

The advantage of both basic and compartment jacket BCD is that on the surface the air will settle in a ring around the diver and keep the diver vertical in the water. This keeps your head clear of the water with the minimum of effort.

Wing jacket BCDs use a single compartment shaped as a ring or horseshoe on the diver's back around the air tank. This setup has amazing advantages for keeping the diver horizontal in good trim while under the water. A disadvantage is that it takes more effort to remain vertical on the surface.

If you do a lot of boat dives, and may be waiting at the surface for some time, it may be worth buying a compartment jacket BCD. For divers concerned about buoyancy control and trim underwater, a wing BCD is definitely recommended. 

Harness: How to fit and adjust a BCD 

Adjustable straps are great, it helps you get in and out of your gear without needing to be a gymnast. You should be able to adjust both shoulder straps, and the waist band. 

Make sure the ends of adjustable straps can be secured and are not hanging loose. If your BCD does not offer a solution to this problem then some 1.5cm | 0.6in wide sections from bicycle inner tube, or bungee rings fitted to the fixed base of the strap will allow you to tidy away the loose end. 

Make sure the harness fits comfortably. If you have to fully tighten each of the adjustable straps, then you need a smaller size. The harness fits properly when you only have to tighten each strap by about two thirds for the correct fit. 

Crotch straps keep the BCD from riding up around your shoulders. Crotch straps are not commonly part of a recreational BCD, but can be easily added with some flat straps and a plastic clip. 

D-rings are stainless steel half rings that you can clip gear to. Positioning is important. Ideally you would want four D-rings: one on each shoulder (in line with your armpit), and one on each hip is plenty. Even technical divers carrying multiple gas tanks don't use more than four D-rings.

Rigid back plate

The back plate sits between the BCD and the tank and is the foundation of your dive gear.  Hard plastic or aluminum is most appropriate for recreational divers. Make sure the back plate is durable, rigid and appropriately padded to sit comfortably against your back.

Cam bands/Tank straps

Cam bands are generally Cordura straps with Velcro to tidy away the loose end. The buckle may be hard plastic, aluminum or stainless steel. Hard plastic is lightweight and rarely fails. Stainless steel is heavier but allows greater tightening and resists damage. Aluminum is rare but is lightweight for travelling and has all the advantages of stainless steel.

Integrated weights

Integrated weights are a great innovation, they take the drag of your weight off your lower back and make for a much more comfortable dive. That said, there is a lot of rubbish out there. Integrated weight pouches break and get lost all the time, and they can be expensive to replace.

Key points to note when selecting an integrated weight system:
- Durability of fabric to withstand the wearing from solid lead blocks;
- Ease of use, make sure you can easily insert the weight pouches by yourself, with your gear on, while wearing gloves;
- Secure lock - this might work great in the shop, but will you be able to clip it in as easily once the plastic has been worn and damaged from hard use? Velcro fades and loses its effectiveness, soft plastics both expand and wear away, hard plastics snap;
- Inevitably, ease and cost of replacement.

It is best to think of integrated weight pouches as consumables similar to car tyres. You can go a long time without replacing them, but they will need to be replaced eventually. How you treat them will determine how often you have to replace them.

Trim weight pockets

Some BCDs come with small pockets on the back just large enough to fit a 1.36kg | 3lb lead block each.  These are great for distributing weight, especially if you can manage with just 2.7kg | 6lb of weight and will be able to use the trim weight pockets alone rather than integrated weight pouches or a weight belt.

Sometimes these are located on the tank strap itself - this is not a good option as it will greatly increase the concentration of weight along the center of the diver's back causing a tendency to rollover in the water. 

Trim weight pockets should be located on the BCD, on either side of the air tank for improved stability in the water.

Pockets  

Your BCD should include one or two pockets for cleanly stowing accessories, and internal d-rings or lanyard for securing accessories. 

A technical diver will generally have one, maybe two, thigh pockets to carry necessary accessories. A recreational diver who needs more than two pockets is carrying unnecessary gear.

Integrated Regulator (Secondary Air)

Some BCD’s feature a second stage regulator integrated into the inflator. The idea is to allow removal of the alternate air source (aka octopus, backup regulator) from the regulator set. This is a terrible idea and a failure of contingency planning. 

The whole point of the alternate air source is to share gas with a diver who does not have sufficient gas to reach the surface safely.  You are, by definition, in an emergency scenario at this point and both divers will be experiencing elevated stress.  

You cannot both breath from a BCD integrated regulator and control your buoyancy. It is a terrible failure of contingency planning to find yourself taking a regulator from the mouth of a near panicked out-of-air diver in order to dump gas and avoid a runaway descent, or add gas and avoid fighting a negative buoyancy descent. 

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