How much weight to use?

As a very new diver I am having trouble with bouyancy. At 180 pounds how much weight should I be carrying in my BC? How much is too much? Is the weight supposed to take you down andyou use the BC to stop decent? What abuot going from fresh water to saltwater, what is the weight difference? I am going to Cozumel in June and want to know how to prepare.

TBH, this really should have been covered in your OW course.

If you have access to a body of water, get kitted up with a nearly empty cylinder and get into the water. Have somebody hand you weights. On each weight, stop finning and with an empty BCD take a big lungful of air. If you sink down until the water surface is at eyelevel then you have enough weight. If you don't sink to this level then you are underweighted. If you sink like a brick then you are overweighted. Keep adding weights until you get it just right. If you do this test in freshwater then add about 2kg,(4lb), for use in saltwater.
Weighting really is an individual thing. Although there are rule of thumb methods that will work approximately, the above will work for YOU. As you progress in your diving and become more comfortable underwater you will find that you can use less weight.

HTH

PS every time that you add/subtract or change your kit configuration then you should do the above weight check. You won't!:) but you should.

Thank you for the info RubberChicken. I will try it 1st chance I get.

First of all, the new diver who does not have trouble with buoyancy is very rare. It takes experience to master it, though working with an instructor specifically on matters of buoyancy and weighting can make your learning curve a bit quicker to overcome.

Secondly, you need as much weight as you need. Different people need different amounts. Besides that, the exposure protection (wetsuit, drysuit) you are wearing will make a lot of difference, as will the question of whether you are diving with steel or aluminum tanks, in salt water or fresh water.

You will often see on scuba diving discussion boards self-proclaimed gurus spouting opinions about what is too much weight. They are deluded if they think they can simply pontificate about how much weight is "too much" without actually doing the buoyancy check with the diver. Weighting is a very individual thing, and you can only really tell exactly how much weight you should carry by experimenting. Remember that weighting is not a contest nor a proof of proficiency. Without enough weight, even the most experienced diver will have difficulty on a dive.

Here's a quick guideline for a weighting you can start working with--add or subtract weight as needed for your specific case:
At 180 lbs, your basic weighting, wearing a lightweight shorty in salt water, might be in the range of 10 to 13 lbs., depending on your proportion of body fat. Add 2 lbs for every 1mm of wetsuit thickness you wear above a 3mm, though at Cozumel in June, you may only need a 3mm. Add about 4 lbs. to compensate for a light cylinder at the end of the dive so that you can maintain a safety stop at the end of your dive. So now you are at 14 to 17 lbs. If you are diving with a steel tank, you might need less.

Now go jump in the water--experiment. Take a breath from your reg, hold it, and release the air from your bc. You should sink a bit, and then "float" with the top of your head a little under the surface of the water if your tank is filled with air. If you keep sinking (don't!) you have too much weight. If you don't sink, you may need more weight. I say "may" because a lot of new divers unconsciously fin towards the surface while they are trying consciously to descend. Of course you can't have it both ways. Keep your feet still when you are trying to descend.

Then go dive with the weight you have determined is more or less correct. If you cannot hold a safety stop at the end of the dive--that is to say, either 1) you can't stay down no matter how hard you try, and you are finning downwards with your head down and feet up, or 2) you have to fin or add air to your bc in order not to keep sinking, your weight is still wrong. You will need to either add (for the first case) or subtract (for the second case) and try again the next dive. With experience, you may find that you gradually drop some of your weight--even a couple of pounds per dive--as you relax in the water. Your breathing gets better, your trim gets better, your finning gets better, and you are not just a big balloon underwater that needs to be held down with *lots* of lead.

Finally, your question about adding air to stop your descent. Yes, that is what happens. As you go deeper you need to "compensate" for the ambient pressure by putting air in your bc--just a little, usually--to get neutral. This is why we call the device you wear a "buoyancy compensator."

When you get to Cozumel, be honest about your experience and ask for guidance in weighting. Ask the DM to bring along a bit of extra weight on the dive in case you need it as your tank gets light. We are used to carrying extra weight for students and new divers, no problem.

Enjoy Coz!

First, I'll not disagree with what has been said here. As has been intimated, proper weighting is important for the end of the dive, when the tank weight will be it's lightest and is going to "suck" you up. This is refered to being "positively buoyant". Hence the requirerment for checking with a tank pressure of 500 psi. I am disturbed that you percieve the weight as being necessary to get you to depth. You should have kick a couple of times to start your descent, and then gravity and water pressure will do it's job. Remember Boyle's Law? It is imperitive to remember that weight meant for the end of the dive, not the beginning.

Thanks to all that replied.

very true to all but proper weight was way way more important before bc were used. I'm not saying it's not important now but it's easier to deal with now then it use to.

Something else to consider chuckwoody is that as you do more dives and gain more experience you will begin to relax in the water column. As you start to relax you will find your self requiring even less weight to hold your stops. I started out diving close to 30 pounds of lead with a single AL 80 and light wetsuit. I can still float well enough to take a nap in any body of water, but surprisingly I can hold my stops with no lead what so ever required these days.