Safely diving with heavy tanks

[seeker242]

but what do you di if there's no weight to drop?

Swim up. It shouldn't be difficult, unless you have a horrible fitness level, to swim up a HP100.

The solution is a "balanced rig". The main saftey point being that you can swim it up to the surface if you were to have a complete bcd failure.

Balanced Rig | 8/of9 | Scuba Buoyancy Masterclass

 

[Diver-Drex]

I can swim up two lp85s or two hp100s (3442psi). I carry no added weight in SM and a 5mm wetsuit. However, I can’t tread with them for very long. Shooting a bag and coming up the line, if your not at the anchor line, is much easier and I have something to hang on at 15’ and on the surface waiting to get picked up. There is a lot of benefit to having some means of redundant buoyancy. I can’t think of a reason not to.

As to AL100s, IMO they are a poor choice compared to a hp100. The buoyancy is nearly identically full and empty. But the hp100 is not as big in diameter, not as long and weighs 13lbs less. I gave my AL100 away.

 

[2airishuman]

So probably stupid question... but how do you safely dive a heavy tank? You of course hear about finding dead people with their weights still on but what do you di if there's no weight to drop?

I dive in a rash guard, steel 72 and minimal weight, 4-6 pounds. 8 on a fat day I'm not a floater... I'm looking at getting trained for nitrox and want a larger tank too take advantage of it. But looking at the #s. I might end up negative with no weight whatsoever. What's the emergency plan in that situation?

I have dived LP72s and HP120s with a rasher, 3/2, 3mm, 7mm, in freshwater and in the ocean. I currently have nine LP72s and six HP120s, from various manufacturers and eras.

It is my experience that, with valve, LP72s empty are neutral, and HP120s vary from 1 to 4 pounds negatively buoyant depending on manufacturer (PST are more nearly neutral), with some additional manufacturing variation from one cylinder to the next. I've measured empty cylinders underwater with a scale, so I believe this is accurate.

I use a steel backplate that is 6 pounds negative. In the ocean I can dive with a rasher and an HP120 and be properly weighted with no lead. In freshwater I am slightly overweighted in a 3/2 with the backplate and an HP120 even with no lead, so I avoid that combination and use the LP72s instead or the 3mm two-piece wetsuit. I typically don't dive in freshwater with just a rasher because when it's warm enough for that the viz is terrible, but when I do, I do it with the realization that I'm overweighted -- which means I will only dive over a hard bottom less than 35'.

I have established that I can swim up a full HP120 with an empty BC under the conditions I dive in.

I am prepared to ditch my kit, either at depth or at the surface, should that become necessary due to a BC failure.

I carry a large SMB that can provide up to 25# buoyancy, on almost all my dives.

On deeper dives I carry a spool of line that is useful in controlling ascent in the event of a BC failure, either in conjunction with the SMB, or by attaching it to ditched weights or ditched kit.

If I am diving with a pony cylinder, I am prepared to ditch my kit and ascend on the pony cylinder.

In those rare situations where I am diving a wall or over a black layer I don't want to go through, or over a bottom that is unsafe due to its depth or other hazards, I make sure I can become positively buoyant in the event of a BC failure by ditching lead.

 

[Nathan Doty]

I honestly didn't know this would be a divisive topic and in appreciate all the input. Im not concerned about getting up, I swim up fully deflated as is, only add air for the safety stop. Im concerned about staying floating if im negative, tired. And then stressed and have a slow boat although ultimately I'd rather pay someone to retrieve my rig from the bottom than be recovered myself I'd still prefer to have neither happen.

With 72s my bottom and air matches, but I'm at ow depth. I want deeper and longer, there's a bunch of wrecks I want but can't get to until I go advanced. I don't want advanced until I go nitrox and have more gas to take advantage of it.

Any concerns about cave sets are non existant because that's not going to happen but wreck penetration is on my list, which I know is similar.

I carry a small smb already, that could help. I have a BIG one, but it's a hose inflate and I don't usually take it.

Im diving palm beach on the 24th, I'll try minimizing as much as I can at the end so I have a solid number to base the math from. Then I'll try I'll try to find somewhere that rents the tanks im after and see if the math plays out.

It's probably something I'll get past in time but even a 2lb safety net would make me feel better.

Although to be fair my thyroid is all out of whack, so I'm probably floatier than usual

 

[Diver-Drex]

@Nathan Doty - It’s not a divisive topic, just someone was posting incorrect information. Your head is in the right place. Do the weight check and see what you need.

With where you plan on heading in your diving a pony bottle is a good (essential in IMO) add on for advanced depth dives. That will add a few more pounds. It seems you know already that you need to have a means to be positive at the surface in case of a bcd failure. That big smb makes sense in terms of lift and visibility. Get comfortable using it at the surface and deploying it from depth.

 

[Bob DBF]

O.P. I think I should address your main concern. Going from a steel 72 to a steel 100 or a steel 120 will not alter your boyancy by any more than 1 to 2 pounds more negative. If even that. I use steel 100s and steel 120s and they are within a half pound of each other in negative boyancy

This is incorrect. The difference in negative buoyancy between a steel 72 and a steel 100 or 120 is 6 or 8 pounds respectively.

Depends on the tank.

My Faber MP 120's are around -7, but a PST E7 100 3445# and PST HP 100 3500# are around -1, and the new Faber HP 100 & 120 are are around neutral, with their LP steels being positive. Don't have time to find every tank but...

I dive a balanced rig, and when I don't I take redundant buoyancy.


Bob

 

[NAUI Wowie]

You seem to be very opinionated on this topic. Your strong recommendation to use 100 cu-ft aluminum tanks is NOT something I would repeat - and I used those tanks for a long time before selling them - they suck compared to a nice steel tank. but the above topics are primarily opinions.

However, your comment about a steel 120 being no different than a steel 72 (other than 1-2 lbs) with respect to buoyancy is not factual. It is a potentially dangerous piece of mis-information. Even if the two tanks had identical buoyancy characteristics (which they don't) the differences in their volumetric capacity translates to a large buoyancy swing between full and empty.

Edit.. post above was written when I was writing mine..

were both correct. first off if you are in philippines or mexico and you want more air you go with an AL100 i dive both in those places. and an AL100 is recommended OVER an AL80 if you need more air.

second i dive also in CA and the difference in boyancy between the 100 steel and the 120 steel is negligible.

you can go in depth regarding different tanks but if you are say talking current faber steels then you are wrong. if you want to use some different or older steels you are correct. But the point you are missing is the O.P. can buy any tank they want. which means they can buy a steel 100 with boyancy characteristics VERY similar to the steel 72 they use now.

 

[NAUI Wowie]

OP hasn't decided on tank. Therefore a very real possibility that he wont need weight in the future.

The question was what happens when you have no ditcheable weight - the answer is get redundant lift. I dont understand why you think that is such an odd thing. I do not dive with weight....

you choose not to carry weight as you set yourself up nuetrally boyant without it. thats your choice but you are in the 1 percent of divers. not normal. and thats fine but lets not go saying its normal to not have weights. there are many experts in scuba on this forum. many EXTREMELY experienced folk.

Those people do NOT represent 99 percent of divers. please tell me how many people you see diving with REDUNDANT lift in normal scuba scenarios.... i have never ever seen one single diver do it. ever

 

[NAUI Wowie]

I can swim up two lp85s or two hp100s (3442psi). I carry no added weight in SM and a 5mm wetsuit. However, I can’t tread with them for very long. Shooting a bag and coming up the line, if your not at the anchor line, is much easier and I have something to hang on at 15’ and on the surface waiting to get picked up. There is a lot of benefit to having some means of redundant buoyancy. I can’t think of a reason not to.

As to AL100s, IMO they are a poor choice compared to a hp100. The buoyancy is nearly identically full and empty. But the hp100 is not as big in diameter, not as long and weighs 13lbs less. I gave my AL100 away.

the only reason I brought up AL100s is that its the only thing you can use for more air in tropical locales. If it seemed I am recommending the o.p. to buy an AL100 that is not the case. I think steel tanks are preferable and that is what i have bought for california.

I am saying that if the o.p. is uncomfortable with large steel tanks if they can only find very negatively boyant steels then the o.p. can use as an alternative an AL100 and i promise and AL100 WILL NOT kill the o.p.

al 100s will not kill you. ive used and use them plenty in third world countries. totally safe stuff maynerd. trust me.

 

[helodriver87]

you choose not to carry weight as you set yourself up nuetrally boyant without it. thats your choice but you are in the 1 percent of divers. not normal. and thats fine but lets not go saying its normal to not have weights. there are many experts in scuba on this forum. many EXTREMELY experienced folk.

Those people do NOT represent 99 percent of divers. please tell me how many people you see diving with REDUNDANT lift in normal scuba scenarios.... i have never ever seen one single diver do it. ever

At some point, the gear is negative enough that weight isn't just unnecessary, it's dangerous. That happens much sooner with large steel tanks and thin exposure protection. Which is exactly the scenario OP brought up. It's very easy to knock all your ditchable weight off the belt with equipment choices. At that point, you have to be able to comfortably swim it up or bring redundancy.

If you've never seen anyone use redundant lift, you're either diving with poorly trained divers or in an environment where common gear choices make it unecessary, like tropical AL80 diving. It's actually a pretty common practice.