figuring proper amount of weights

Question
I was certified last year, and did so in a 7 mil farmer john. I had a very hard time submerging, but once I did I became neutrally buoyant okay, enjoying all six dives over two days.
However, I had to use 36 lbs of weights. My dive buddy- who was also in my dive class-and I are going diving on 6/10, and I now have a 3 mil suit. Ideas about amount of weights to use?

Answer
Hello Wes, proper weighting is essential for enjoying the dive as well as for your own safety.  Being properly weighted also helps you breath your air in an efficient manner.  Many students have some initial difficulties with proper weighting.  As you gain more experience you may find your weighting requirements will diminish somewhat.

Your weighting depends on your body type and mass, your gear (especially wetsuit and tank), and the water (fresh or salt).  I have included a table below that can help determine the initial weighting you can try.  It is very conservative and you may be over weighted.

Your instructor should have showed you a proper way to determine if you are correctly weighted.  To recap:  on the surface, with your regulator in your mouth, without kicking or using your hands, take a deep breath and let all the air out of your BC.  You should be floating at eye level in the water.  If you now exhale the breath you held you will sink.  If you sank right away before releasing the breath you have too much weight.  If you do not sink after releasing the breath you have too little.  Adjust you weight in small increments until this works.  If you are diving with a 80 cubic foot aluminum tank, you will then need to add 4 more pounds (because it becomes more buoyant as it empties).

You mentioned you had some difficulty descending.  Be sure to equalize your ears on the surface then let all the air out of your BC and just as it empties out exhale hard to release the air in your lungs.  If properly weighted you should easily descend.

Here is the weight estimate calculator.  Have fun diving!!  Jesse

a.   Exposure Suit Type         Weight
1)   Swimsuit or skin      1 ?4 lbs
2)   3mm one piece or shorty      5% body weight
3)   5mm one or two piece      10% body weight
4)   Add hood and boots      2 lbs
5)   7 mm two piece         10% + 4 ?5 lbs
6)   Dry suit with light underwear   10% + 3 -5 lbs
7)   Dry Suit with heavy uw      10% + 7 ?14 lbs

b.   Fresh or Salt Water
Body Weight            Add from fresh to salt
1)   100 ?125 lbs         4 lbs
2)   126 ?155 lbs         5 lbs
3)   156 ?186 lbs         6 lbs
4)   187 ?217 lbs         7 lbs

c.   Tank Types
Add or subtract weight according to empty buoyancy
Type         Full Buoyancy       Empty
1)   AL80      -1.4 lbs      +4.4
2)   AL100      -4.35         +3.0
3)   St HP80      -8.5         -2.5
4)   St HP100   -8.5         -1.0
5)   St HP120   -9.5         0