Almost all scuba divers will require some kind of lead weight to balance their own natural positive buoyancy. Cold water divers usually require large amounts of lead and as a result, knowing what kind of weighting systems are available is useful when selecting a weighting system to purchase. Let's first examine some of the weighting concerns.

Neutral buoyancy at the surface is normally acquired by selecting enough lead weight so that a diver bobbing on the surface will float with their mask just below the surface of the water upon exhaling and then float with the mask just above the surface upon inhaling (this test must be done in the actual open water environment with all gear on, buoyancy tuning done in a pool will not be correct for salt water).

However this neutral buoyancy may not be desirable for practical reasons. The first concern is the tank the diver is using. Steel tanks have different buoyancy profiles than aluminum cylinders. When a steel tank is full of air it is roughly 6-7 lbs. negatively buoyant and when empty becomes about 3 lbs negatively buoyant. Aluminum 80 cylinders however are about 3 lbs. negative when full and become 3 lbs. positive when empty (larger aluminum cylinders become even more buoyant when empty). This means that at the end of a dive, a diver who is neutrally buoyant with a full tank now becomes positively buoyant at the end of a dive. This can make doing a safety stop at 15 feet of water difficult and potentially could lead to a runaway ascent during the last 30 feet of water (the most critical zone where ascent speed must be controlled). A prudent diver will then add at least 3 lbs of lead to counter the buoyancy profile of an aluminum tank.

If a diver is wearing a drysuit, runaway ascents are a greater risk if the diver is not constantly purging air from the suit upon ascent or if he or she cannot purge it fast enough. As a result being a little more negative than neutral (above and beyond countering buoyant empty aluminum cylinders), may be desirable to help prevent runaway ascents and to help make safety stops easier to perform. This overweighting though is a delicate balance. Too much weight can stress a diver both physically and mentally while too little weight can make ascent control and safety stops problematic (too much weight can also exceed the buoyancy limits of your BCD and exposure suits making ascent at depth problematic, uncontrolled sinking may result).

All beginner divers should keep in mind that fine-tuning of weight should not be done right away. It is difficult to say when to attempt to do it but after doing a significant number of dives, a cold water diver can usually trim at least 5 lbs. of lead off of their belt. This is usually due to anxious beginner divers not exhaling completely upon descending. Humans usually have an expiratory reserve capacity which is an amount of air in the lungs that remains after a person has exhaled. With effort, a person can still exhale more air. Thus with experience, a diver who is more accustomed to the underwater environment can learn to exhale the expiratory reserve capacity when descending. This means that less lead is required to allow a diver to comfortably descend when this skill is learned. Until this skill is learned, it is best to leave fine-tuning of your weighting system to a later date.

Once you have determined how much weight you need, the next step is to choose the weighting system. Warm water divers with very little lead weight can really choose any kind of weighting system without any real concern. Cold water divers however should not concentrate all of the lead weight in one location. Because of the large amount of weight worn by cold water divers, concentrating it in one place would mean that in the event of requiring the ditching of your weight system would result in a dramatic change in buoyancy that is likely to result in uncontrolled buoyant ascents leading to injury. Breaking up the location of weights allows a diver to ditch fractions of the lead weight thus permitting a more controlled buoyant ascent (i.e. breaking up the weight into separate pockets with 25% of the weight in each can allow a diver to ditch 25% of the weight at a time rather than 100%). There are many weight systems that when used in conjunction can make cold water diving more comfortable and safer.

The oldest form of weighting is the use of hard lead weight belts. These belts use a nylon webbing belt with hard lead blocks attached to it. As a diver descends and the exposure suit compresses, these belts can become loose and may slip off of the waist. Because of this disadvantage, some belts have bungee cords woven in to take up the slack of a belt when an exposure suit is compressed.

Hard lead weight belts are the cheapest system but are also the most uncomfortable as the hard lead block does not conform to the body's shape very well.

Hard lead weights may be coated with vinyl for cosmetic reasons and for some protective value. Dropping a lead weight on a boat deck or other sensitive area can be more damaging that dropping a vinyl coated lead weight of the same weight.

Releasing this kind of weight system results in the loss of all the weight stored on it.

While bulkier than the compact lead blocks, lead shot is usually contained within a sealed pouch either forming part of the belt (Seasoft belts) or placed into pockets within a belt. Lead shot being able to move, allows the pouches to conform to the form of the body and thus makes it more comfortable to wear (especially for women).

These belts are often less durable than hard weights as the weight pouches are usually made of neoprene and are sensitive to abrasion damage. Pouches made of materials like Dyna-Hide offer higher durability than the neoprene counterparts.

These weight belts are significantly more expensive than a hard weight belt but for repetitive charter dives, they are well worth the money.

Releasing this kind of weight system results in the loss of all the weight stored on it.

DUI and other companies make a weight belt that also includes a suspender harness. This makes wearing the belt while standing or diving vertically or diving horizontally easier as the pressure of the weight is spread out across the shoulders and the waist rather than just the waist. An additional advantage is that the weight is located in two independent pouches that can be deployed one at a time. This means that 50% of weight instead of 100% can be deployed from this weight system.

Some BCD's come with a weight system forming part of the BCD. While the BCD is heavier for a buddy to help a diver to get into, the system has two primary advantages. The first is that when a BCD is inflated, the lead weight is physically supported by the BCD and not the diver's back. Comfort in the water is unparalleled with this system.

The second benefit is that weight integration usually concentrates weight in two locations on the BCD allowing 50% of the weight to be deployed at a time (some exceptions like newer Zeagle BCD which use a single rip cord to deploy the weight leading to the loss of 100% of the weight). This again is important for cold water divers who don't want to have an uncontrolled buoyant ascent when ditching their weight system.

Ankle weights are minor weighting systems that allow divers to trim the weight balance. Drysuit divers will often find that their boots are too buoyant leading to a head down position while diving. Ankle weights can make the boots neutrally buoyant and can help to re-distribute some of the lead weight from the weight belt to the legs.

Also a minor weighting system, these weights allow a re-distribution of some of the lead weight from the weight belt to the tank. This weight is then supported by the buoyancy of the BCD and results in more diving comfort. However do not place too much weight on the tank as it can make the tank have a tendency to flip a diver onto his or her back when rolling to the side (a characteristic of heavy steel tanks). Also try to locate the weight in the center of the tank so as to avoid excessive force causing the head or the feet to dip below the horizontal.

Some divers with a bit of ingenuity, use the hard packs within a BCD (for mounting a tank) to store lead. By drilling a small hole into it, moderate amounts of lead shot can be used to fill the hollow interior. This in effect makes the hard pack a quasi-integrated weight system.

Keep in mind that a diver should not place the majority of the weight in a hard pack as this source of weight cannot be deployed in the event that positive buoyancy is required leading to a potentially dangerous situation.

Cold water divers are recommended to combine multiple weighting systems so as to allow the deployment of fractional amounts of weight at a time rather than all at once. For example a diver that locates 30% of the lead on a weight belt, 50% in an weight integrated BCD (with the ability to deploy 50% of this weight independently), and the last 20% in ankle weights and/or tank weights and/or hard pack weights, has lots of flexibility for ditching fractional amounts of weight in an emergency.

Another reason that this kind of weight distribution is desirable is when a diver is in an overhead environment. Should an opening be too small for a decked out diver to pass through, exiting the tank pack and sending the pack through first might be required. However, a diver in an exposure suit exiting a pack without any lead weight on their person will quickly become positively buoyant and may float away from the negatively buoyant pack. Thus distributing the lead weight allows egressing a pack to be safer as neither the diver or the pack will be as likely to float away.

Distribution of the weight also makes it easier for a buddy to help you put your weight integrated BCD onto your back.