Best time to do the weight check

I had a quick q about weight check. I know that it basically involves selecting the correct weight so you float eye level in the water with normal breath but it's impractical to do this prior to every dive.

At least for me I can't get access to a salt pool before a dive (i'm guessing weight check in a regular pool will turn out to be wrong) so do you usually go through a trial and error process for a few dives until you determine the correct weight to use? Once selected assuming the exact same gear (wetsuit, boots, fins etc.) can I always rely on using the same weight for all dive sites/conditions?

-salt water is around +3, do a check in fresh water if possible and at least get yourself close. Of course you want to do this with near empty tanks.

-Yes if you aren't changing any gear/water (salt vs fresh) you can use that for every dive, just remember to do the check with empty tanks otherwise you'll end up light at the end of the dive.

You can always check your weight at the end of the first dive. Hang there on the back of the boat adding/removing weight until you get dialed in.

I recently got back into diving after many years and used the "10% of body weight plus 5 lbs" rule (that's with a 7mm wetsuit, hood, gloves and booties).

It worked out pretty well right away but I was able to fine tune my buoyancy at the end of the dive. That method is a great starting point.

Pool = fresh water, which has a lower density than salt water.

First, optimize your weighting in a pool (ideally with a near empty tank). Then weigh yourself + all of your dry gear. Calculate 2.5% of the weight of yourself + all of your gear. (This will probably be around 6 lbs.) Add this amount of extra lead to your configuration before your next salt water dive. This method should get you very close to the appropriate amount of lead for ocean diving.

I'd recommend doing a proper weight check at the end of your next ocean dive.

Have fun out there...

k374:

I had a quick q about weight check. I know that it basically involves selecting the correct weight so you float eye level in the water with normal breath but it's impractical to do this prior to every dive.

At least for me I can't get access to a salt pool before a dive (i'm guessing weight check in a regular pool will turn out to be wrong) so do you usually go through a trial and error process for a few dives until you determine the correct weight to use? Once selected assuming the exact same gear (wetsuit, boots, fins etc.) can I always rely on using the same weight for all dive sites/conditions?

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This is a good starting point. To fine tune your weighting you need to check it with the tank down around 500psi. At 10' you should be neutrally buoyant with no air in your BC. If you have to add air, you're too heavy. If you can't stay down you're too light (make sure ALL the air is out of your BC.)

Carrie

You only need to do this part once:
Go to a pool wth all your scuba gear, including tanks you commonly use, drained down to end-of-dive pressure.
With just your bathing suit, fins, mask (& snorkel if you use one), see how much you weigh.
Write that down.
Get in the pool and see how much weight you need to sink you with a near full breath.
Write that down, too.
Weigh your wetsuit dry and write that down; take your wetsuit & pull it completely under water to make sure there's no air in it, then pile weights on it until it just barely sinks.
Write that down too.
Do the same for all your stuff that floats, writing down how much it weighs and how much weight is required to sink each item.
For stuff that sinks, you can use a balance or a pulley to determine how much weight it's worth by seeing how much submerged lead it takes to lift it. Write these weights down as negative numbers.
Transfer the weight and the weighting values for each piece of gear to a "weighting sheet" that lives in your logbook.
--
Once you've got this weighting list completed, you simply add the numbers algebraicly for you and the stuff you're wearing/carrying to get your fresh water weight requirement.
For salt water, total the weight of you, your stuff & the fresh water weights you need and then (as Bubbletrubble has already said) add 2.5% of that.
This may seem like a lot of work for such a routine problem, but if you'll go to the trouble of creating a weighting list once, (and update it as you add new gear) it allows you to accurately calculate your weight requirements for any combination of gear you want to use every time with no guesswork, very quickly.

P.S. Oh, yeah, for a dry suit you'll need to put it on & see how much it takes to sink you with each set of underwear you use...
Rick

k374:

I had a quick q about weight check. I know that it basically involves selecting the correct weight so you float eye level in the water with normal breath but it's impractical to do this prior to every dive.

At least for me I can't get access to a salt pool before a dive (i'm guessing weight check in a regular pool will turn out to be wrong) so do you usually go through a trial and error process for a few dives until you determine the correct weight to use? Once selected assuming the exact same gear (wetsuit, boots, fins etc.) can I always rely on using the same weight for all dive sites/conditions?

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Best time for weight check: With 500 psi (assuming al 80). This represents the amount of air left in your tank at the end of your dive. You want to carry just enough weight to hold a 10' safety stop with 500 psi, but no more. More weight would necessitate more air in bc at bottom, more work involved displacing a larger volume of water every time you kick, and subsequently more air consumed and higher sac rate.

Difference between salt and fresh is 6 lbs appx, meaning that you must add approximately 6 lbs when you move from fresh to salt. A football player sized guy might need another pound, a wisp maybe a pound less. 6 is a good average number.

No, you don't need to do a check each time. Keep good records. My log book has a weight page indicating weight necessary for 3, 5, and 7 mil suits in both fresh and salt water. It is also helpful to keep a record of gear that might be carried with you such as reel, pony bottle, lights, etc. Any change in thermal protection or gear carried will result in different weighting.

I got my weight set for my steel tanks. Haven't done a check in 2+ years, though I've gotten advice to do so. My equipment hasn't changed and hovering is a breeze. I add 6 lbs. when using my buddy's AL 80s. I find that I am a bit more buoyant toward dive's end due to their positive buoyancy as opposed to steel. I will be using an AL 80 next year, so a couple more pounds may be in order. Definately will be time for a weight check.

dkktsunami:

...You want to carry just enough weight to hold a 10' safety stop with 500 psi, but no more.

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Noooo........ This bad procedure made it into at least one major agency's weighting advice a few years back (so dkktsunami can be excused for recommending it ) - it was bad advice then and it's still bad now. You want to be able to control your buoyancy all the way to the surface! You need just enough weight to be neutrally buoyant at the surface at the end of the dive - which can be a bit (up to a couple pounds) more than the minimum needed at 10', depending on your anti-exposure suit.
Rick