What size tank (Steel) would you purchase for nitrox fills?

[scubadiver888]

As people have noted, the 130 is really heavy out of the water. I find an AL80 worked okay for my air consumption. The HP100 @ 3000 PSI holds more than an AL80. If get get a full fill (3442 PSI) it is even better. If you want more air, the HP119 holds 123 cu.ft., it isn't longer than an AL80 and isn't quite as heavy as a HP130.

I have one HP119 for deep, dark, heavy current dives and two HP100s. I'm very happy with them.

If your SAC rate is too high for these to work for you, I would recommend improving your SAC rate. If you are fit then look at trim, buoyancy and technique.

 

[danvolker]

I think an HP 130 is a piss poor choice... too heavy/negative, period.
On the other hand, a low pressure 120 has pretty good bouyancy charicteristics, and plenty of shops will fill the 2450 psi rated 120 to more like 3400, giving you something more like 170 cu ft !!!

Also....if you are interested in using Nitrox, and getting the longer duration dives at 80 to 100 feet deep, and 80 cu ft tank is stupid for anyone....it is almost shocking the industry and everyone on SB is not againt this outdated mis-use.

80 cu ft tanks were great for air...

....But with the longer bottom times possible in the 80 to 100 foot range, they do not leave the majority of recreational divers enough reserve for themselves---and NO WHERE NEAR ENOUGH reserve for their buddy!!!! If you believe in the buddy system and in coming up with a reasonable reserve of gas, you need to choose the much larger tank.

Double 80's are a solution to someone who has a bunch of them, and does not want to lose the investment....they have good bouyancy charicteristics....the problem will be :

• You need a differrent / larger wing , typically a 40 lb lift wing for doubles ( wider)
• You need to go out on dive charter boats than can easily handle your set of doubles plus your tank(s) for the second dive of the day...this being problematic on the vast majority of diveboats...some have room for a 2nd set of doubles to be stored under your seat--this is the best solution you can really hope for, and then you just switch over after first dive....going with a 2nd single tank means having to change to a singles wing or different BC, as you DO NOT want to use the same BC or wing for both doubles and singles diving.
• Many people will hurt themselves with the lifting of the double tanks--it is past a critical threshold of how much the average diver can carry around without injuring their back. They are also more of a pain to get filled, and cart around...This is why the LP 120 is such a superior choice...the extra weight is not so much that it gets dangerous for most people for the increased weight, and the enormous extra gas supply means you can be a much safer diver.
• The double 80's will make you higher drag and slower in the water....the lp 120 will allow you to stay "slick' and fast if you ever need to be.

 

[melanie.]

I think an HP 130 is a piss poor choice... too heavy/negative, period.
On the other hand, a low pressure 120 has pretty good bouyancy charicteristics, and plenty of shops will fill the 2450 psi rated 120 to more like 3400, giving you something more like 170 cu ft !!!

The 130 weighs 43lbs
The 121 weights 49.9lbs .... so not any lighter

The 130 has 9.7lbs buoyancy shift
The 121 has 9.1lbs buoyancy shift ..... not what I would call significantly better

I have dove many times with a 121, that is a frickin long tank. I mean ya I am really short but even on guys under 6' it is not the easiest to handle. Especially if you only have 1 camband, then the tank likes to pull and "roll" you over in the water. Yes you eventually get used to it but it takes a while.

To decide on a tank you have to decide what is most important to you. Is it cubic feet, length of tank, weight of tank, how about efficiency of tank weight (ie lowest pounds per cubic feet), buoyancy shift (must it remain neutral or negative?), will you be going to doubles later and want one that is easy to double up etc...

So take your time and figure out what is really important to you. Because what you need today might not be what you need in a year or two. I made my decision based on length of a tank and cubic feet, because I need the extra air for deep dives and I am not going to get any taller. Good luck!

 

[TSandM]

Dan, your advice is great for diving Florida's reefs, but the OP is in SoCal, and if he wants to do long dives at all, he will be in a dry suit.

At your size, Ulfheddin, I think an HP130 would be an excellent choice. It's what most of my SoCal friends are using. The tanks ARE heavy -- almost 50 lbs dry weight when full -- but if I can manage to haul them around, you can. My understanding is that good HP fills are not an issue in SoCal, although finding Nitrox may be.

An HP130 will give you a decent amount of bottom time as a new diver with high consumption, but it will also be a good tank (with adequate safety margin) for deeper dives, when your experience leads you to them.

I guess I could sum it up by saying we own six of them . . .

 

[scubadiver888]

Actually, if you are getting a cave fill (170 cu.ft. In a LP121), the buoyancy shift is greater than a properly filled HP130 because the buoyancy shift is really the weight of the gas you breath.

So the LP121 doesn't even have the slightly smaller buoyancy shift.

 

[danvolker]

The 130 weighs 43lbs
The 121 weights 49.9lbs .... so not any lighter

The 130 has 9.7lbs buoyancy shift
The 121 has 9.1lbs buoyancy shift ..... not what I would call significantly better

I have dove many times with a 121, that is a frickin long tank. I mean ya I am really short but even on guys under 6' it is not the easiest to handle. Especially if you only have 1 camband, then the tank likes to pull and "roll" you over in the water. Yes you eventually get used to it but it takes a while.

To decide on a tank you have to decide what is most important to you. Is it cubic feet, length of tank, weight of tank, how about efficiency of tank weight (ie lowest pounds per cubic feet), buoyancy shift (must it remain neutral or negative?), will you be going to doubles later and want one that is easy to double up etc...

So take your time and figure out what is really important to you. Because what you need today might not be what you need in a year or two. I made my decision based on length of a tank and cubic feet, because I need the extra air for deep dives and I am not going to get any taller. Good luck!

Maybe there are some weight differences between brands of LP 120's..... I have a couple of HP 100 steels, that are ridiculously heavier in the water, than my OMS lp 120... The Hp100's are ok for my dry suit, but in summer, if I try to use them with an 18pound lift Halcyon wing, it takes the entire 18 pound lift of the wing to get me neutral ( also wearing a light cannister--this is only other wieight beyond steel BP).
With the lp 120, it takes about half of my lift potential in the 18 pound wing...still not good, but feasible if needed....
My solution was to start using a Halcyon 30 pound wing witht he 120's, and only use the 18 pound wing in the winter, with a drysuit.

But I like that I "can" use the lp 120 with either wing, and don't have to use a drysuit with it...

As usual, TS&M is right....for the use in the colder waters the poster has, as long as he is always in a drysuit, the 130 may be just the ticket....I don't think it would be good with a thick wetsuit--it would be at least as lame as my hp100's would be--causing the diver to be extremely heavy if they hit 120 feet for more--possibly dangerously heavy. Then again, some divers will never want to dive deeper than 60 feet, so for them, this may not be much of a problem.


But I expect others here will agree the 80 cu ft tank for nitrox and deeper than 75 feet, is a mistake everyone needs to fix

 

[Akimbo]

Tank size is mainly a compromise between capacity and how much weight you are willing to carry. Generally speaking, capacity that is low enough that you are not likely to enter staged decompression is a good target for recreational divers — using whatever safety margin you are comfortable with. Nitrox will usually let you increase the capacity by about one size due to reduced decompression requirements.

Maximum weight can change a lot between a rocky shore entry and a boat dive. At some point, the weight becomes great enough that a small set of doubles might be worth considering. Personally, I would rather dive a set of twin-65 or 72s than a 130 because of better balance and redundancy options — but a 130 puts me way into decompression much deeper than 50'.

Your air consumption will almost certainly improve considerably so 0-24 dives may not be the best time for you to make this judgment. Look at what other experienced divers are using in your area and let that guide your probable usage once you have a little time in the water.

 

[TSandM]

Dan, do you by any chance have a couple of the Faber HP100s that are -7 when empty? Those would be really awful tanks for where you dive. My HP100s are -1.5 when empty and I would have no hesitation diving them in warm water.

Ulfheddin, if you want to try borrowing a 130 and seeing if it works for you, I'm sure you can find one in your area. Depending on where in SoCal you are located, you might PM HBDiveGirl (she's in Hermosa Beach). She has several.

 

[danvolker]

Dan, do you by any chance have a couple of the Faber HP100s that are -7 when empty? Those would be really awful tanks for where you dive. My HP100s are -1.5 when empty and I would have no hesitation diving them in warm water.

Ulfheddin, if you want to try borrowing a 130 and seeing if it works for you, I'm sure you can find one in your area. Depending on where in SoCal you are located, you might PM HBDiveGirl (she's in Hermosa Beach). She has several.

Lynne,
All I know ( or can see on the 2 tanks) are the XS scuba indication....just hit the web page for them, and they show 2 models..one is the faber....and mine are at least the 14 pounds negative they indicate.... for my drysuit, this was great last winter-- I needed zero extra weight with these tanks, so the dry suit diving became much simpler.

As much as these tanks cost though, it stinks they are so incompatible with good gear matching choices in summer, in S Fla.

The lp 120's I think are 2 pounds negative at 2640 psi, and about half a pount negative when near empty. I don't mind going in a little negative. Functionally they dive more like an Al 80 in bouyancy charicteristics ( how it feels to dive them), but with up to twice the gas potential!!! And then there are the shops that just can't be relied on to give you a high pressure fill for your HP tanks...particularly the ones that fill the tanks dry, hot, and in a hurry...with the low pressure tanks, you get "accidental fills" that are over 3000 psi, and are always happy

 

[Ulfhedinn]

The Calc shows that my RMV is 1.2CF/min.

I do love diving deep <80-100'> but don't mind playing in the shallows either. Most dives with the little lady are in the 20-40' range. I don't have a drysuit that I own just a 7mm. I will be doing some dry suit diving this coming weekend to see if I like it. Going to check out the Yukon out of SD.

I own 2 80alum but was just looking over my options. I hate renting tanks... there is a freedom in taking off when ever I get the itch to dive.

50lbs worth of tank or ruck for that matter isn't an issue. I was just looking to get the most out of my time in the drink.