Weighting - salt->fresh w/farmer john?

In So-Cal (salt water), I typically dive with ~17lbs, AL80, 7mil wetsuit, with hooded vest, booties, & gloves. While on vacation, my hubby and I went diving in a quarry (fresh water) for the first time, where they suited us up in Farmer John style wetsuits. However, when we asked what the weight conversion would be from salt->fresh, they suggested 28lbs, which rather appalled me.

Does this sound about right? Could a farmer john wetsuit actually add on THAT much weight over my usual neoprene setup? I feel like the dive shop was treating us like unskilled new divers (despite the fact that we told them we dive regularly here in So-Cal), or they just like to overweight their divers (I also heard another employee tell a similarly built person the same weight estimation).

oh, and just for reference, i'm 5'6", 135lbs.

Thanks!

I added a step in 7mm vest and hood (no arms or legs) over my typical 7mm wetsuit for some cold water diving in saltwater. It added 8 lbs to my weight needed (I was shocked). So it is possible, but that seems like a lot. You can typically subtract 4-5 lbs for fresh water, so closer to 20-22 would seem more accurate to me with the added neoprene.

It actually isn't unreasonable. We dive Farmer Johns up here, and fresh water tends to call for 32-34 lbs. We are both bigger, but a FJ does add a lot of neoprene.

First, everyone is different and there is no exact formula. With that said, I'm with merxlin. Using the basic weight guidlines for your weight, you would drop 5 pounds going from salt to fresh. I can't see the farmer john making that big of a difference over a full suit but that's my opinion.
Personally, I would have a problem with someone telling me how much weight I need instead of letting me figure it out.

Even though I think they overweighted you, did you feel overweighted once you got in the water? Were you able to do a buoyancy check? I'm curious how that much weight felt to you.

Yes that's TOO high. Probably not incredibly unreasonably too high but it is definitely too high. If you dive 17lbs 7mm in salt, you subtract 2.5% of TOTAL weight (gear + you) from your weightbelt requirement. I don't know what the weight of all your gear is but with your weightbelt and you, plus a few for gear, you are probably removing 4-5lbs from your belt. that's 12-13lbs now. Now you are adding an extra partial layer of 7mm to your wetsuit for a farmer john. 7mm neoprene requires somewhere between 2-3 lbs of lead to offset it's buoyancy per pound of neoprene at the surface. This is VERY rough, but EVEN still, with your size, I doubt you are going to need 15 extra pounds to offset that extra farmer john jacket. You probably really only needed in the low 20s.

In freshwater I use WELL under 30lbs (total negative weight) in a drysuit and I'm 5'7" 165lbs.

merxlin:

Even though I think they overweighted you, did you feel overweighted once you got in the water? Were you able to do a buoyancy check? I'm curious how that much weight felt to you.

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oh yeah, dropped like a rock in the water. There wasn't really an easy way to do a bouyancy check and dump weight at the site, so I just filled up my BC quite a bit, tried to find my happy neutral spot, and got on with the dive.

I know I was way overweighted, I think what's really bugging me is that I'm trying to figure out if the dive shop wasn't giving us enough credit as tourists, or if they were really giving it their best guess. An extra lb or two, okay, but that much extra weight just seemed extreme.

Anyway, thanks for the responses!

Are you diving in the same gear (less wetsuit) in both locations? Your gear, not just wetsuit, add or subtract weight needed. Your log book is an excellent place to track weighting in different diving conditions using different accessories (light, camera, etc, etc).

Going from salt water to fresh water you generally drop 4-5 lbs as other have suggested. Switching from a 7mm suit to a farmer john could be a HUGE difference. You're essential adding two wetsuits with the amount of neoprene.

Now, 17lbs in a 7mm suit to me seems like a large amount to me but each person is different. Each persons body composition is different. I use 4 lbs of lead with a 7mm in salt water just so I have some ditch-able weight. My complete gear setup and body composition dictates that.

Knowing that you subtract about 4-5lbs for fresh water and not knowing how the farmer john would effect things, a good starting point would have been 17lbs of weight since that is what your normally dive with. From there add or subtract as needed.

My guess is that you could have probably used 17 - 20lbs total.

If you visited a tourist type dive operation they may just have given you a figure based on what the average diver needs that they "service"..

17-20 sounds dead on to me too, maybe low 20s to be safe.

I dive with 4lbs on a belt as well if diving wet in a wetsuit but that's because most of my weight is in my back plate and tank. Total negative weight ends up being like 16lbs wet.

I agree, a dive operator would probably want to go on the super negative side with tourists since they have no idea what the skill of the tourist is even if they tell them. Better to be over weight and compensate than the customer complaining that they couldn't dive at all because they couldn't get down or worse, they popped up and embolized or got bent.