Weighting systems
0 of 4 hands-on
01 Introduction
Most divers are naturally buoyant, and a wetsuit and a cylinder add to it. Weights cancel that, so you can sink and stay at depth. Getting the amount right is one of the most important parts of comfortable diving. Too little and you cannot descend. Too much and you work harder, use more gas and damage the reef.
Objectives
- Explain why divers need weight and what affects how much they need
- Compare weight belts, integrated weights and other systems
- Describe how to check your weighting and why you must be able to release it
02 Watch
Finding your weight
4 min · Video in production
- 1
A diver at the surface, floating at eye level with an empty BCD and holding a normal breath.
- 2
The same diver exhaling, and slowly sinking.
- 3
A weight belt, an integrated weight pocket and trim weights on a cylinder, each shown in use.
- 4
A diver releasing weights with one hand at the surface, and floating up easily.
03 Learn
Why you need weight
A diver's body, a wetsuit and a cylinder that is nearly empty together float. To descend and stay down, the diver adds lead weight until the whole system is just buoyant enough to hover. A good rule is that at the end of a dive, with a nearly empty cylinder, a diver should still be able to hold a stop in shallow water without effort.
What changes how much you need
| Factor | Effect on weight needed |
|---|---|
| Thicker or newer suit | More weight, because there is more neoprene to float |
| Drysuit with undergarments | More weight, because of the gas inside |
| Salt water instead of fresh | More weight, because salt water is about 2.5% denser |
| Aluminium cylinder instead of steel | More weight, because aluminium becomes buoyant when nearly empty |
| Body type and lung volume | Varies from person to person |
| Extra equipment such as a camera or a light | May change weight needed, and trim |
Weight systems
- Weight belt: lead blocks threaded on a belt with a quick-release buckle. Simple and easy to adjust, but it can slip and put pressure on the lower back.
- Integrated weights: pockets in the BCD with quick-release handles. Comfortable and common, but the BCD holds more weight, and divers must make sure the pockets are fully clipped in.
- Trim weights: small weights on the cylinder or on the harness, to help balance a diver and keep them horizontal.
- Soft weights: lead shot in pouches, which are gentler on the body and easier to carry.
A simple weight check
- 1.Put on all your kit, with the BCD empty and the cylinder about a quarter full, or have an assistant simulate that.
- 2.In the water, hold a normal breath. You should float at about eye level.
- 3.Breathe out fully and slowly. You should begin to sink.
- 4.If you do not sink, you need a little more weight. If you sink while holding a normal breath, you have too much.
- 5.Adjust in small steps, and note your total weight for each exposure suit and cylinder combination.
Predict first
A diver wears much more weight than they need, 'to be safe'. What is the likely result?
Weight distribution and trim
Where the weight sits changes how a diver lies in the water. Weight on the hips can pull the legs down. Weight on the shoulder or high on the back can lift the legs. Moving a little weight, using trim weights or choosing a different cylinder position, helps keep a flat, horizontal body that is efficient and reef-friendly.
Take a guess first
A diver weighs 6 kg of lead in fresh water. In salt water, which is about 2.5% denser, a suit might need about 1 kg more. If the diver also changes from a steel cylinder to an aluminium one that needs a further 2 kg, how much lead might they now need in total?
Handling lead
- Lead weights are heavy. Lift them correctly, and watch your back and your feet.
- Wash your hands after handling lead.
- Never drop weights from a boat or jetty, and secure them so they do not fall.
- Store lead securely and safely, away from children.
04 Explore
Try it yourself
Put the steps of a weight check in order.
Put the steps in order.
- 1Breathe out slowly and check that you begin to sink
- 2Hold a normal breath and check that you float at eye level
- 3Put on your kit, with the BCD empty and the cylinder about a quarter full
- 4Record the weight for this suit and cylinder
- 5Adjust the weight in small steps
05 Apply
Scenario
A diver comes to a new site in a rented 5 mm suit and an aluminium cylinder. Last week, in their own 3 mm suit and a steel cylinder, they used 6 kg. The dive guide says, "Just use the same as last time."
What is the best approach?
06 Check
07 Summary
Key points
- Weights cancel the natural buoyancy of the diver, suit and cylinder.
- Suit, water type, cylinder material and body type all change the weight needed.
- Weight belts, integrated weights and trim weights each have strengths. Release must be easy and clear.
- Check your weighting whenever your kit changes, and avoid over-weighting.
Before you apply this in the water
- Have I been trained by a qualified instructor for this?
- Am I medically fit to dive?
- Do I have a buddy and a plan?
- Am I diving within my training and limits?
Answer every question in the Check section to mark this lesson complete.