Scuba BCD
Purpose
A BCD (Buoyancy Compensator Device, also called a BC) serves two essential functions: it holds your scuba tank securely on your back, and it allows you to control your buoyancy at the surface and throughout your dive. By adding air to the inflatable bladder through the power inflator (or orally), you gain positive buoyancy; by releasing air through the dump valves, you sink or maintain neutral buoyancy. Mastering your BCD is central to good diving — a diver with excellent buoyancy control uses less air, avoids contact with the reef, and dives more comfortably.
Features
Style
There are several different styles of BCDs and each will satisfy different needs and individual preferences.
A jacket style BCD is the most common one, especially in dive shop rental fleets. The bladder wraps around the back and sides, providing buoyancy around the diver's torso. Jacket BCDs are intuitive to use and stable at the surface. They tend to push the diver into a slightly head-up position underwater, which may be more comfortable for some divers, but does make maintaining good, horizontal trim more challenging.
A back-inflate style BCD will have the bladder bladder is positioned only on the back, which makes it much easier to achieve a horizontal swimming position (good trim) underwater. This style eliminates the bulk at your sides and is popular with more experienced recreational divers who prioritise streamlining and trim.
A wing & backplate style BCD utilizes a modular system of gear including an inflatable wing that attaches to a backplate and harness system. The wing & backplate system is used by recreational and technical divers and can be configured with different parts depending on the diving you're doing. Switch out the wing for a doubles wing for diving twin tanks or switch out the backplate between stainless steel and aluminum. Integrated weight pockets can be added or removed from the waist webbing as well as the tank bands depending on your requirements.
A sidemount BCD allows you to wear two tanks positioned at your sides rather than on your back. While this style has been most popular with cave and wreck divers, it has become popular with recreational divers who like having the extra tank of air and the buoyancy stability that sidemount provides.
Difference between a back-inflate or wing & backplate BCD and a side-inflate or jacket-style BCD:
Integrated Weights
Most BCDs will have special pockets for weights so that you can distribute your required weights across your body. Besides wearing a weight belt on your waist, you can put weights on your back (trim pockets) or on the side of the BCD. This will help your "trim" in the water (maintain horizontal position). Check the amount of weight that each pocket will carry to ensure you have enough space to carry the weight that you need.
Other Design Considerations
D-rings provide attachment points for accessories like dive lights, reels, slates, and SMBs. More is generally better — look for metal rather than plastic D-rings for reliability.
Cargo pockets with easy-access closures are useful for carrying safety gear and small accessories during the dive.
Adjustable straps are usually found on the shoulders, chest area, and waist area. These ensure a more comfortable and secure fit. The cummerbund that wraps at the waist area is usually adjustable as well.
Tank bands on the back of the BCD are what hold your tank securely to your body. You will have either 1 or 2 tank bands on your BCD, depending on the brand and style. The buckle on the tank band is either plastic or metal, metal being the more reliable and strong choice.
Some BCDs are specifically designed for women in mind with extra room around the hips and chest area as well as narrower shoulders and shorter torso length.
Care & Maintenance
After each dive, rinse your BCD well with fresh, clean water to rid it of any salt, sand, dirt, or chlorine. Give the power inflator a good rinse to get rid of any sand or salt that is caught under the buttons. Regularly rinse and clean the inside of the bladder by adding water and BCD cleaner to the inside either through the power inflator or over pressure releases. Rinse the bladder well, drain any water from the inside, add air to the BCD and store it slightly inflated. Your BCD should have a thorough inspection by a professionally trained technician at your local dive shop every 1-2 years or 100 dives. A BCD servicing will include testing the bladder to ensure it holds air, cleaning and repairing the power inflator, inspection of straps and other parts.