The Importance of Proper Weighting

By Gemma Smith

So you have certified as a new diver and want to get in the water diving and practicing as soon as possible. You remember from your introductory scuba diving course all the main skills you learned. There is just so much fun stuff to work on and improve upon when diving! It’s all too easy in the enthusiasm of wanting to get UNDER the water to forget that a large part of what makes your life easier as a diver takes place BEFORE you even first start your descent. Proper weighting is, without a doubt, one of the most important requirements for the competent diver. It, unfortunately, seems to be one of the most commonly overlooked though. I worked for a year in one of the busiest dive centres in the Caribbean. The problem that reared its ugly head, again and again, was novice, and sometimes even experienced divers, having problems because of incorrect weighting. If you are willing to take the time though it is actually one of the easier adjustments to make. Get it right and it will without question bring on your skills as a diver in leaps and bounds.

Why is weighting so important anyway?

Proper weighting really is the solid base on which we build safe diving skills. It allows us to fine tune and control our buoyancy. This means controlled descents. It means a smooth and well-positioned body position on the dive. It also allows a slow and steady ascent and safety stop at the end of the dive. Correct weight means less drag, better trim, and normally a reduction in gas consumption (SAC rate). Too much weight, on the other hand, has the risk of a fast descent. This may result in mask squeeze, ear barotrauma, or in going deeper than your planned maximum depth because of too speedy a descent. It will also make buoyancy control much more difficult. An over-weighted diver needs to add more air to their BCD to try and get neutral, but this will only force them to make more buoyancy adjustments as the air expands and contracts with depth changes. Too little lead, on the other hand, has issues if you don’t actually have enough weight to safety ascend slowly and hold your stops. As Goldilocks said about the Three Bears’ porridge in the famous children’s story, weighting really needs to be ‘neither too much or too little, but just right’.

So where do I go from here?

The easiest way to check your weighting is to do a weight check at the beginning and end of your dive. It’s simple:

  • Once floating comfortably in the water at the start of your dive make sure your mask is on and your regulator is in your mouth. While in the vertical position take a breath in. No need for a large lungful of air, just a normal breath.
  • Hold your breath (while it is NEVER ok to do this underwater, for checks like this one on the surface it is safe).
  • Use your BCD inflator to dump all the air from your BCD. Make sure you keep hold of your inflator so if you start to sink unexpectedly quickly you can add more air and become positively buoyant again. For those divers wearing drysuits, fully open your exhaust dump, and vent your drysuit of air.  
  • The general idea is that when properly weighted you will float at eye level at the surface while holding a normal breath
  • Now breath fully out. You should sink past eye level and start to slowly descend on that exhalation. Although it is tempting, try and resist the urge to fin or scull with your hands. Doing this will not give you a real measure of whether or not the weight you have on is correct.
  • Return to the surface of the water and repeat the exercise with less weight. A properly weighted diver should just be able to get under the water when they exhale. Your descent should be in control and stable, not a plummet to the depths.
  • If you found you couldn’t descend comfortably add more weight in small increments. Keep adding until you can complete the weight check with ease.

Do a weight check at the beginning of the dive to make sure you can start the descent. Don’t forget though that your scuba cylinder will become more buoyant throughout your dive as you use the air. Perfectly weighted at the start will mean underweighted at the end, so adjust accordingly. The aim is to be able to hold your safety stop easily at the end of your dive, with little or no air in your BCD. Also, think about whether you are diving a steel or aluminium tank. While steel will have a slight change in weight when less full of air, the change in weight of an aluminium cylinder is more significant.

My weight is now perfect so I’m done, right?

Well, not exactly. To be weighted properly is a continual trial of experimentation and adjustments. Change exposure suits or what you are wearing, change the cylinder size or gear configuration, or change the environment? What you need in terms of weight will change. A thicker wetsuit or more thermals under a drysuit means you will need more weight in order to sink. Diving in fresh water for the first time when you normally dive in the sea will mean less weight. After all, seawater is denser than fresh. Achieving proper weighting is an evolving process, and one that you will probably adapt and change many times over your dive life. More diving experience and becoming more relaxed as a diver may even result in a change of weight, as your SAC rate goes down over time. Like all the skills we have in our diving toolbox, just completing them once is not enough. Repetition and fine-tuning is needed to truly become capable and confident as divers. While a simple weight check may seem unnecessarily basic for the more experienced diver, it is part of the solid foundations we first learned as new divers. It is these entry-level skills that enable more advanced and complex additions to be competently added to our diving repertoire over time.

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9 replies
  1. Ric Goodman
    Ric Goodman says:

    A boiyancy check at the start of a dive is not adequate. As a starting point, a 12l / 80cft tank will contain around 3kg/6lbs of compressed gas, which is significant. If one sets weights to just descend when full, one if definitely going to be underweighted soon into the dive. So when the article advises: “Perfectly weighted at the start will mean underweighted at the end, so adjust accordingly.” this means adding the corresponding 3kg weight for each cylinder carried.

    Then to have a more accurate check, one needs to repeat the weight check with nearly empty cylinders. You need to know that you can stay submerged with 20 bar in each of the tanks that you carry, or you risk breaking your decompression stop.

    The statement “While steel will have a slight change in weight when less full of air, the change in weight of an aluminium cylinder is more significant” is not true. The difference in buoyancy is dependent on the weight of gas inside the cylinder, irrespective of the material of its container.

    Reply
    • Ivo
      Ivo says:

      I agree about the change in boyancy between steel and aluminum cylinder, the latter is more buoyant no doubt but the change is really the same and depends on the gas weight. I have seen this being said so many times, and could never figure why. Only thing that comes to mind, is the simple fact that most aluminum are11.1L (or 80 cub.f. US) and steel are 12L, and often both are rented out as being the same. Or I am missing something 🙂

      Reply
      • Nathaniel Wilson
        Nathaniel Wilson says:

        Yes you have it. My suggestion would be to actually weigh your tank when it is full and when it is empty. I own a high pressure 100cuft tank which changes by 7lbs. I am guessing the a low pressure 80cuft might only change by 4lbs. I also find it very handy to keep notes in my electronic dive log on how much weight I used with various set ups. This makes it good reference when I get to a new location.

        Reply
    • Nathaniel Wilson
      Nathaniel Wilson says:

      Yes the Weight of the Compressed Air in the tank is very important. This varies with the amount of pressure and the size of the tank. My steel high pressure 100cuft tank weighs 47lbs when filled at 3,200psi. When it gets down to 500psi it only weighs 40lbs.

      Reply
    • Todd
      Todd says:

      Thank you Ric Goodman!!! You have added to this article what EVERY article on buoyancy should include, the factor of adding weight for each cylinder carried. Most all articles on how to establish buoyancy or how to perform a weight check fail miserably in helping new divers understand how they WILL become underweighted shortly in their dive; thus, creates frustration for the new diver not knowing correct buoyancy procedures.

      My wife, daughter-in-law and I have been certified for 2-years. Buoyancy was our primary issue. We don’t know anyone who dives so we read articles and depend on reader/subscriber input…like yours. Initially, we read many articles similar to the one we’re commenting on; however, none of them mentioned the factoring of cylinder weight. So as a beginner we established buoyancy as suggested in the article, the dive was perfect…for a few minutes. Shortly in to the dive, each of us began messing with air/deflation in an effort to maintain buoyancy but minutes later we surfaced with great frustrated as to why we couldn’t stay underwater…what did we do wrong?

      I eventually figured out my error of not factoring the cylinder’s weight during the initial weight check but it was too late for my daughter-in-law…frustration prevailed. Some may argue such buoyancy techniques are taught in Open Water courses. Though buoyancy is taught, the curriculum in at least two of the most popular certification courses is not in such detail to describe exact steps, what must be factored and what can influence weight variances (i.e., type of gas in the cylinder). I’m sure there are many instructors who go above and beyond curriculum requirements by explaining correct/proper procedures to determine buoyancy. Unfortunately, not all instructors go above and beyond which is why articles such as this, which targets new divers, must be accurate. This article, as-is, leaves a new diver frustrated as they float on the surface unable to descend minutes in to their dive. Again, thank you Ric for providing the needed and additional insight of establishing buoyancy successfully.

      Reply
  2. Phil Smith
    Phil Smith says:

    I believe too much emphasize is put on being overweighted. A good diver has to be able to dive overweighted, sometimes grossly so.
    The idea that you have to put more air and then keep adjusting, therefore using more air, is nonsensical. Good trim and weight management in key.
    Example: This weekend whilst diving Race Rock off Southern Vancouver Island, this first dive I got quite cold so for the second dive I added another four pounds of lead. Second dive was much warmer, it allowed me more air in my dry suit. Air consumption unchanged, trim also unchanged.
    Learn to manage weight and trim and how you add and subtract air.

    Reply
    • Nathaniel Wilson
      Nathaniel Wilson says:

      Cold water diving in a dry suit and taking a boat anchor of weight to get down. My hat is off to you cold water divers!. My 7mil with hood and gloves is good for bottom temps of 55 degrees which is about as cold as it gets in So Cal. I much prefer warm water venues, diving in board shorts and a rash guard, and changing out weights to see how light I can go.

      Reply
    • Todd
      Todd says:

      Hello Phil, I understand what you are saying and believe it to be true for more advance divers like yourself and others who may be categorized as a “good diver” which usually follows experience. I feel the target audience for this article is new/beginning divers like myself. As a new diver (2nd year), I live inland where my opportunities to dive is limited to freshwater with one or two Coastal trips each year. Not being able to dive nearly as much as I would like, I am finally starting to understand buoyancy and how to manage both my weight and trim. However, to understand and establish buoyancy throughout a dive is extremely difficult as a new/beginner; especially for us who have no other divers with experience to teach us outside the basic Open Water curriculum. Hence, the reason new/beginning divers search out articles such as this one…sadly, it was misleading as was every similar article I have read (failed to factor cylinder weight). The odds are significant for an overweighted new/beginning diver to descend much faster and further than their qualification and abilities allow. A new/beginning diver is trying to remember everything taught while trying to maintain buoyancy so when overweighted is factored in to the dive, the lack of experience most likely will overwhelm the diver causing them to loose focus of crucial skills as they blindingly focus on buoyancy. I personally have bobbed at the surface not understanding why I couldn’t descend since I followed the exact steps as outlined in similar articles. Additionally, lack of knowledge and experience resulted in being overweighted at times as I blindly descended too fast thinking my buoyancy was okay. As a new/beginning diver, establishing and more importantly, maintaining buoyancy has been the biggest hurdle in my quest to become a “good diver.” I have heard/read the same for so many new/beginning divers. Just an opinion from a new diver’s perspective.

      Reply

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