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Scuba diving weight check: How to do it the right way

Great buoyancy starts with getting the weights right. Learn to do a pre-dive weight check.

By 10 Min Read
Scuba divers descending in pool.

Today, we are going to have a closer look at how to properly do a diving weight check, also called a buoyancy check.

We check out the reasons for doing such a scuba weight check, explain the right techniques, and point out common pitfalls.

This includes the pre-dive weight check, as well as some more advanced tips and tricks.

Introduction to the scuba diving weight check

One of the most common questions I get during a dive course or before one of our dive trips goes something like this:

How much weight do I need on a scuba dive?

Similar ones are “how do I determine my scuba weight” or “how much weight do you recommend at (insert diving spot)“. These are indeed good questions and almost all scuba diving forums are full of them.

To be honest, the above questions can all be answered in a pretty straightforward manner:

Do a pre-dive weight check!

What this is and how you do it the RIGHT way is going to be the topic of today’s post.

Scuba divers equalizing ears while descending
Optimizing your scuba weight will reduce air consumption, improve your buoyancy and make you a better diver!

During a weight check, you determine if the amount of weight you are carrying is optimal for diving. In most cases, this boils down to picking the right number of weight pieces in addition to your scuba equipment.

A pre-dive weight check helps you determine the right amount of weight for each scuba dive.

Making sure you have the right amount of weight during a dive is very important for achieving perfect buoyancy underwater, improving your scuba fin kicks, and reducing air consumption.

A demonstration of the weight check should be part of every beginner diving course like the Open Water Diver or the CMAS*. However, we often notice that many students have never done or even heard of it.

Scuba instructor demonstrating skills underwater
An instructor will show you how to do a proper weight check during your Open Water Diver course.

If so many divers don’t ever do a proper weight check, you might wonder: Is it really necessary to worry about it at all?

The answer to this question is very clear: Yes!

You do need to do a weight check before scuba diving at a new dive spot.

Let’s see why that is the case.

Why do a pre-dive weight check?

It’s simple: A weight check before diving will help you determine whether you have the right amount of weight on you. This includes optimizing your dive equipment, suit, extra weight pieces, and tank, as well as the distribution of the weight along your body.

Firstly, unnecessary weight on your belt or in your pockets makes carrying the equipment much more difficult than necessary. If you reach the water already semi-exhausted from heavy scuba gear you are bound to feel stressed out and breathe in more heavily on your descent.

The additional weight also means you need to inflate the BCD more underwater, leading to more resistance and less streamlined aerodynamics.

This extra drag can account for wasting up to 20 bars or more during a dive.

Knowing the right amount of weight to put on will reduce your air consumption, lead to better trim and buoyancy in the water, and ultimately make you a better diver.

That’s the reason why some people also call the weight check “buoyancy check”.

A pre-dive weight reduces air consumption, leads to better trim and buoyancy, and makes you a better diver.

Of course, you can trust the instructor’s intuition and experience in determining the weight you should need.

He or she has most likely seen hundreds of students of similar size and equipment setup as yours to ensure you are not completely off with the weights.

However, instructors and dive guides usually prefer to pack on a little extra weight to make sure students have no problems descending quickly.

Underwater photographer scuba diving under boat.
Make sure to carry the right amount of weights to balance out any equipment like underwater cameras etc.

Therefore, doing your own weight check is the best way to optimize this to your needs.

How to do a scuba diving weight check?

Doing a scuba diving weight check includes three steps:

  • Pre-dive weight check: Determine the right amount of weight before descending on a dive.
  • Post-dive weight check: Check the amount of weight during the safety stop at 5 meters depth.
  • Optimize the weight and repeat the above steps until you find the perfect amount.

Pre-dive weight check

Finding the right amount of lead weights is of course easier when you have a reference. This could be a prior dive at the same location, notes from your logbook, or your experience in general.

The weights depend on the type of water (you need more weights in salt water), the thickness of your suit (a thicker suit means more weights), the type of tank, and your own body weight and height.

10% +-1kg / 2lbs rule

If you have no idea where to start, try using the 10% +-1kg / 2lbs rule of thumb for lead in saltwater and around 2/3 of that in freshwater.

So if you weigh 70kg (155 lbs), try out 8 kg (18lbs) of lead weights at first in saltwater.

This is also the estimate we use in freshwater, where we would start off with about 6kg (13 lbs) in the same scenario.

There are more accurate ways to determine this, but for a new diver, the above rule accounts for heavy or nervous breathing as well as an overly inhaled state throughout the dive.

Luckily, I built the perfect scuba diving weight calculator so you can accurately determine the number of weights you need to use on your next dive.

Pre-dive weight check at the water surface

With your first estimate for the weights, walk into the water the way you learned it during your Open Water Diver or CMAS* course.

That means fully inflated BCD and making sure you don’t step on any corrals or vegetation.

Now begin with the pre-diving weight check following these steps:

  1. Float at the surface without moving your feet or arms
  2. Make sure your feet point downward
  3. Take a big breath and hold it (not too big though and only during the weight check!)
  4. Completely deflate the BCD without moving your legs
  5. You should sink now, but only until the water covers half of the mask
    • If you sink further: You carry too much weight
    • If you don’t sink far enough: You carry too little weight
  6. Remove or add extra weight and repeat the process until the water reaches eye level
Scuba divers at surface
Your weight check starts at the surface.

Sometimes you might be at a point at which you are not entirely sure if you reached the right level. In this case, don’t worry. This is not an exact science.

I recommend you start the dive and see how it feels underwater, after all, that’s where it matters most. If you have a hard time descending, this might be an indicator to take more weights with you next time.

Don’t forget though that you can compensate for missing weight by breathing out during the descent.

The purpose of adding lead weights is to help our descent while underwater they serve no purpose. Therefore, being slightly underweight is a good option for experienced divers to save a little more air while scuba diving.

It looks roughly like this:

However, do not make the mistake of being completely underweight! This will lead to strong positive buoyancy during the ascend and can become dangerous if you are not able to control your depth during safety or decompression stops!

That’s why the weight check includes a second step which we will look at now:

Post-dive weight check during the safety stop

The second -and often neglected- part of the scuba diving weight check happens during the safety stop.

Normally, we end every dive with a safety stop at 5 meters (16 ft) for 3 minutes when we reach 50 bar in our tank.

This allows us to outgas more nitrogen and decrease the risk of getting decompression sickness (DCS). In shallow reefs, most divers simply use this time to check out the pretty fish some more or take some final pictures.

However, if this is your first dive at a new location, you should be doing a post-dive weight check right now.

At exactly 5 meters (16ft) and with 50 bars left in the tank, your BCD should now be completely empty while hovering motionless in the water.

Scuba diver hovering underwater
Hover motionless during the safety stop with an empty BCD to know you have the right amount of weights.

If you notice there is still a considerable amount of air left in order to stay buoyant, you can take off weight on your next dive.

If you have to exhale more than usual to prevent floating up, you are definitely positively buoyant and need to add extra weight.

Please make sure that you are always in control of your buoyancy throughout this exercise and don’t do this during mandatory decompression stops or in currents.

Extra tip: Simulated Empty Tank exercise

The following exercise is one I do with many of our students in their beginner courses and it’s also a favorite among our Dive Leader and CMAS*** tests.

Instead of doing our weight check during the actual safety stop, we can simulate an empty tank situation by doing the following:

  1. Descend to 5-7 meters (15/16 ft) depth without touching the bottom
  2. Take a big breath, as if you are getting ready to do the “regulator out” drill
  3. Deflate the BCD (and potentially your dry suit) completely while hovering at the same depth
  4. Squeeze out every last bit of air trapped inside!
  5. While exhaling remove your weight belt or weight pockets and hand them to your buddy
  6. You are now simulating the 50 bar (“tank empty“) situation from above without risking ascending too quickly during the actual safety stop
    • Just like before, you should not need to kick your fins or exhale excessively to remain at the same depth. If you do, you need to adjust your weights accordingly.
  7. Don’t forget to get your weights back from your buddy now. 😃

Please try to avoid any kneeling on the bottom during this exercise! If you have the option to go to a pool or indoor dive center, practice it here before.

Some more tips for your scuba weight

By now you should have a very good understanding of how to do a proper weight check. As a little bonus, here are some more things you can do to optimize your scuba weight for diving!

Optimize the weight distribution

Buoyancy is one part of the equation, proper trim is the other. Once you found the right amount of lead weights to take with you on a dive, you need to think about how to place them.

If you notice during a weight check that you fall forward or backward, improve the weight distribution before descending further.

Weights should be placed along your center of gravity or help even out discrepancies in any way.

In general, you already have plenty of weight on your back due to the scuba tank.

Therefore, try to push the lead pieces towards your front as far as possible when using a weight belt.

Even better, use weight pockets or back-mount weights to make sure the weights don’t interfere with your diving at all.

Consider the different salinity of water

By now everyone knows that saltwater requires more extra weight than freshwater.

However, not all saltwater is equally…well..salty.

For example, the content of salt in Thailand around the Similan Islands is very high, whereas the salinity on Curacao in the Caribbean is a lot lower.

The Baltic Sea in Germany or Denmark features a salinity that is closer to a freshwater lake than to the North Sea which it borders.

Therefore, although you might be used to a certain amount of weights in saltwater, this can change drastically at a different dive spot.

Man reading in Dead Sea floating on surface
Salinity has a big impact on the number of weights you need. Although the Dead Sea is an extreme example.

If you want to see the levels of salinity across our oceans, check out this cool map released by NOAA, the National Oceanic, and Atmospheric Association.

Take the time to do a proper weight check at each new location to optimize your scuba weight.

Note the weight in your logbook

Write down the amount of weight you used at each location, including the suit type and tank size, so that you have a reference if you ever come back to the same dive spot again.

Use a backplate

Using a backplate greatly helps to optimize the amount of weight you carry around while diving.

A steel backplate will give you extra weight and allow you to ditch the extra lead pieces you had on before. An aluminum or carbon one might do the exact opposite though and require even more than before.

Check out my recommendations for backplate/wing sets for some inspiration.

Summary

In this article, we looked at the weight check-in scuba diving in great depth.

A weight check helps you determine whether you put on the right amount of extra lead weights to be neutrally buoyant throughout the dive without creating too much drag.

Use my perfect scuba diving weight calculator to get accurate estimates of the weights you need.

In the pre-dive weight check, you deflate your BCD completely at the surface while holding your breath. In the optimal case, you will sink down to eye level only.

The post-dive weight check happens during your safety stop. While hovering motionless at the target depth with your 50-bar tank reserve, your BCD should be completely empty.

Use the empty tank simulation exercise to practice the post-dive weight check at the start of your dive.

We also looked at a few other tips to optimize your scuba weight.

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Always dive with friends and happy bubbles. 😃

Cheers

Julius

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