Buoyancy Compensators are usually referred to as BCs or BCDs (buoyancy compensator device). BCs are considered a life support device, like your regulator, so research should be done when purchasing one. BCs are used to provide flotation at the surface and keep you neutrally buoyant underwater. They also hold your tank in place on your back. There are generally two types of BCs on the market today: jacket style and back-inflation (wings).
Jacket style BCs
Jacket style BCs surround your chest area and back like a vest. Basically, the air cell surrounds you. Jacket style BCs are very popular and cost effective and come in two styles: full-jacket BC and contour-jacket BC. The full-jacket’s air cell is around your chest and torso and over your shoulders. The contour-jacket BC is a cut down version with a smaller air cell.
Back-inflation BCs (wings)
Back-inflation BCs are becoming more and more popular among active divers. They have reemerged from the cave diving community and provide some real advantages. They provide less drag and more stability when swimming in a horizontal position. The air cell (wing) is behind your back, which means it does not squeeze or put pressure on your chest when inflated. Back inflation BCs are made up of a backplate that holds your tank, a harness system, and the wing.
A wing type BC is made of an inner bladder, external protective shell, inflator, dump valve, and corrugated hose. The external shell protects the bladder from abrasion or puncturing. The wing BC can be used with double of single tanks and comes in lift capacity sizes ranging from 35 to 100 pounds. Most technical divers use BCs with about 50 lbs of lift. Excessive lift increases the size of a BC and creates more drag. Some manufacturers offer high lift capacity BCs with a bungee cord retaining system designed to reduce the drag of the BC. Some wreck divers and deep ocean divers use two sets of wings or a dual bladder system, but cave divers generally use a single bladder or wing system. If you decide to use two separate wings or a dual bladder system, do not connect the second inflator system. Power inflators can jam open and cause the wing to inflate uncontrollably causing a rapid ascent.
Many of the BC systems are capable of weight integration. This eliminates the need for a separate weight belt. The weight that you need is placed usually in pockets on the BC. The pockets have handles on them so that you can pull and dump the weight quickly if needed. The added weight to your BC can be problematic and put stress on the BC itself. When transporting gear on and off a boat, the BC will be much heavier and be harder to handle. Before diving with a weight integrated BC, make sure you know how it works as each manufacturer makes theirs a little different.
The lift of a BC is the amount of weight it floats when inflated. Lift capacities on BC systems vary depending on the size and style, but can range from 20 to over 70 pounds. The average BC has a lift capacity of 40 pounds. Larger people sometimes need more lift capacity and BCs should fit well, so it’s important to look at and try out as many BCs as possible before buying one.
The air in the BC is added and removed through a valve. There are three types of valves: power inflator/oral inflator, exhaust/dump, and overpressure relief.
The power inflator is what is called a Schrader valve. The power inflator automatically inflates your BC when the inflation button is pressed. The valve also can be used as an oral inflation valve. When you place the opening in your mouth, you can depress the oral/dump button and blow in the air cell to inflate it.
The exhaust/dump valve is used to remove air from your BC. Exhaust valves can be found as pull-dump valves on the lower portion of the BC, in the inflator hose, which can be pulled to dump air from where it mounts to the BC, or the power inflator can be used to dump air.
BCs usually have a valve that automatically dumps air from your BC if you overfill the bladder. This prevents the air cell from popping.
Cost: $150 to $500
Backplate and harness
The backplate and harness mount to your single or dual tank system and are used to carry the tanks on your back. Backplates are made of aluminum, stainless steel, or ABS plastic. Softpac systems also exist and use a padded backpack system. The harness is typically made of webbing material. Some harness systems are simple single-piece webbing harnesses, while others are two-piece designs with padded straps, etc. All most all harness systems come standard with D-ring attachments for you shoulder straps and waist belt.
A backplate and harness system is designed to fit well, be flexible, and provide a low profile in the water. If you plan on using a harness system with thick wetsuits, dry suits, and thin wetsuits, sizing is very important as each exposure suit style requires more or less webbing to fit properly. You don’t want to cut off too much webbing when sizing so that you can’t where your system with various exposure suits. Many technical divers have two or more backplates and harnesses for use with different suits and configurations.
The buckles, D-rings, and other hardware that comes with a backplate and harness should be stainless steel, which is more durable against the elements. Some manufacturers use plastic buckles which aren’t as durable and don’t provide as good of hold on the webbing strap.
Cost: $100 to $200