Tank Shopping Advice..

[jlehigh]

Hey Guru's and fellow aspiring noobs,

I would like to plan for purchasing some tanks in the next few months and I'm wondering if folks can chime in on what to look for and "Good Buys".

I know I want Steel, and I would love to have a shorter High Preassure tank with a Yolk compatible valve.. I see there are high preassure 80's, 100's, 120's ect ect. Most of my diving will be local. I already wear 30-32lbs and would like to not have to add more

I appreciate your input.

[Tangfish]

Steel is good. Tank size depends on your body size, consumption rate and what your typical dive buddies use. There isn't a 'best tank' but there could be a 'best tank' for your size/wt and experience level.

I tend to breathe very little air compared to the buddies I dive with most frequently, so I usually dive an HP80 and bring along a LP95 for my buddy.

You'll want to consider where you're getting your air fills too, when deciding if you want a HP or LP tank. I love the LPs, it's easier to get a good fill, especially if someone else is doing the filling. HPs are nice because they're smaller.

It might help to dive others' tanks first before making a decision.

[DiverDown]

I am kind of an air hog, so I like to dive 119s. But a hp steel 100 is probably about the best bet for a scuba tank IMHO.

[CaptnJack]

If these are your first tanks, go with HP100s or LP95s. Both work well. The hp100s being slightly negative (-2 or 2.5) when empty and the lp95/98s being neutral.

If you are a very big guy with high consumption hp130s are a good choice too. Although doing more dives and getting your SAC down is a better way to go than trying to compensate for inexperience, poor trim, dangly unstreamlined gear, etc. by purchasing huge tanks.

IMO, If you are not in a steel backplate get the 100s to move some weight up higher. If you are in a steel backplate I'd say lp95s are a better bet to avoid moving too much weight up high and tipping you head down.

LP95s are a bit less expensive than HP tanks. Unfortunately, steel tanks are rarely on sale when you want them.

Richard

[lamont]

HP130s all the way.

You can dive to 90-100 fsw for 30-35 mins (on EAN32), take a 15-20 minute multilevel stop at 60-40 and then do enough time above 30 to stretch the dive out to 60-90 minutes, and you can surface with enough gas reserve to deal with surface conditions. You will need an exceptionally good SAC rate to do a dive like that on HP100s.

Taking a standard "pretty good" SAC rate of 0.60:

4 ata * 30 mins * .60 + 2.5 ata * 20 mins * .60 + 1.5 ata * 20 mins * 0.60 = 120 cu ft.

The best SAC I can get without getting a headache is around 0.45, and an HP100 is still only kind of marginal for these dives:

4 ata * 30 mins * .45 + 2.5 ata * 20 mins * .45 + 1.5 ata * 20 mins * .45 = 90 cu ft

So, the 130s will let you do the dives you are doing now which are less aggressive and with a higher SAC rate and will let you grow into more aggressive dives with lower SACs. Females, of course, can consistantly hit lower SACs and could use HP100s instead, but since they're often buddied up with hoovering males they should consider the gas reserves they need if their buddies have a gas problem at depth...

Also, one thing to note is that HP tanks and LP tanks are identically sized except for the service pressure, so that:

LP80 = HP100
LP95 = HP119
LP96 = HP120
LP104 = HP130

Those tanks will be equivalent on your back-strain budget. So if you buy an LP104 and only fill to service pressure its just as bad as lugging around an HP130.

Some shops will fill LP tanks to 3500 psi, which is a florida cave country practice. A lot of shops will not, which makes the HP tanks actually the better deal for getting a good fill (I'll take a 3200 psi "short fill" in an HP130 over a 2600 psi "good fill" in an LP104 anyday).

LP tanks are also much cheaper than HP tanks though, and some people like the buoyancy characteristics of LP tanks in doubles better. For single tank divers, though, who will be getting fills at various different shops, I recommend HP130s. The HP120s and HP119s are close in size and are fine tanks, but I find I can't tell any difference in how they feel on my back, they just give a little less gas (although HP120s are supposed to be good for really tall people, and really short people might like like the 119s).

[Sounder]

As a noob I got 2 hp130's and 2 hp100's. Very happy with them, and they're DIN or K. I prefer the DIN, but like the option for friends. I also have DIN to K adapters on my 1st stages.

If you'd like to borrow one of each and dive/carry/fill them, you're welcome to. I'm high & dry for a while (at least another couple weeks). On the eastside on the Sammamish Plateau if you'd like to come pick one of each up.

Sent you a PM.

[jlehigh]

Excellent info gang! Thank you for taking the time to contribute. I'm still trying to figure out why I dive so much weight, as I'm only 5'9"X185lbs, and solid as a rock okay maybe more like a water bed.. I also dive wet with an O'Neil.

I would classify my air consumption as very good for a noob. I consistently under-breathe folks I dive with at varying exp levels and size.

I didn't realize tank sizing is so related to individual preference. I think testing the tanks out will be the way to go.

[CaptnJack]

At your size a HP119 or 130 is a good option, if you are diving nitrox or plan to dive nitrox. A bit oversized and more money than you need to spend if you are only diving air.

For Edmonds UWP a 130 is just a rediculous amount of gas and fill costs for big tanks can oftentimes be more money than in a smaller tank.

If you aren't much of a deep diver, and you probably aren't (relatively) in a wetsuit, a smaller HP100 or LP95 is still a good choice.

On real shallow dives like Edmonds UWP, I use a hp80 because my SAC drops pretty low when I'm quite a ways inside my comfort zone.

Do you know your consumption now? How many dives under your belt?

Future plans?

Richard

[WylerBear]

I'm 5'8" and 165 lbs and definitely not solid as a rock but in fair to medium shape. I dive with HP80's and have great air consumption so the 80's allow me dives consistently longer than an hour. The only problem with the 80's is that they are short enough to be a little awkward getting into your BC with them. Once they are on, it's great. I have bad knees so when I went from AL80's I did not want the additional weight of the 100's or larger. And as I said, I can get more than an hour off the HP80's with no problem. If you can, try some out and make a decision based on your experience with them.

[lamont]

One thing about going from an Al80 to an HP100/LP80 is that you'll move about 5# off of your waist and onto the tank. If you look at the dry tank weights, the HP100/LP80 should be about 5# heavier, which means that overall your weight getting into the water will be the same between an Al80 and an HP100/LP80. An HP80 will both take off weight on the weightbelt and be less weight overall.

[jlehigh]

Do you know your consumption now? How many dives under your belt?

Future plans?

I don't know my consumption rate, but I have the PC kit to download the info, just need to get my regular PC set-up again (Post remodel).

I have 13 dives in about 3 months..

Future plans are to recreation dive several times a month regularly until I reach 30-50 dives where I'll go ahead and take the advanced class followed by rescue training. Most dives will be local at 85' or less. I like diving my wet-suit, but will be getting a dry-suit for deeper/colder dives later in the year. Did I mention I like my wet-suit?

[Sounder]

I would HIGHLY recommend attending Grateful Diver's gas management seminar at the Federal Way UWS. The information is INVALUABLE and you'll learn how to figure out what gas you need. You'll also learn that going to 80fsw on an 80cu tank isn't always the best idea... especially for a new diver... I sure did.

At the end of the class, I was REALLY glad I can haul around a 130.

[CaptnJack]

Let's take a stab at your consumption together...

On a dive at EUP:
what size tank are you using
how long did you dive
what was your average depth (plus minus 5 ft should be good enough, basically your choices end up being 25, 30, or 35).

[jlehigh]

I'd love to take a gas management class!

Alki Cove2 Dive:
Underwater Sports Rental Tank with 2900PSI
46min bottom time
Max Depth 85'
Avg depth ?40'?
3.5min stop at ~18'
1000 PSI remaining upon surfacing (edit)

[lamont]

I'd love to take a gas management class!

Alki Cove2 Dive:
Underwater Sports Rental Tank with 2900PSI
46min bottom time
Max Depth 85'
Avg depth ?40'?
3.5min stop at ~18'
1000 PSI remaining upon surfacing (edit)

1900 / 3000 * 77.4 = 49 cu ft (al80s are actually 77.4 cu ft)
40 / 33 + 1 = 2.21212 ata (average)

49 cu ft / ( 46 mins * 2.21212 ata ) = .48173 cu ft / min

that's pretty decent consumption, at dive #13 i was probably up around .80 cu ft / min, and i've only recently been able to get down to the .45s...

you'll probably find that you do want to do deeper dives eventually, though. the octo dens that are at 110 off the boundary cable are very popular, and its common to swim between those pilings and the I-beams spending 20-30 mins at that depth.

[CaptnJack]

Well Lamont beat me to the guesstimate. 0.5 cf/min is pretty danged good in a wetsuit. Next time you dive you can make note of these variable and recalculate. Over time you start to understand how much it varies and whether its your guesses at average depth, cold, workload, whatever.

A gas management class can help you understand how to calculate how much gas to bring and hold in reserve for you and your buddy. A good thing and only recently really becoming part of the curriculum - at least informally.

[jeff98208]

i use hp80 ( high pressure 80 cubic feet) steel tanks.

[Grateful Diver]

I'd love to take a gas management class!

Then come to the Federal Way Underwater Sports on Wednesday, October 25th ... class starts at 7 PM and runs about an hour and a half.

Best of all, it's free ... all it'll cost ya is gas money.

... Bob (Grateful Diver)

[Sounder]

Like I said - take the class!!! The really suprising thing is the metric showing maximum depth on several tanks at several consumption rates...

Lesson learned: When I was diving in Hawaii on an Al80, and went to 94fsw (which was really easy to do in the "fish tank" type vis), with my consumption rate I didn't have enough gas to get my buddy and I to the surface should something have happened. ](*,) Would we have made it, probably. Could we have done an emergency ascent if needed, sure. Would we have called DAN as soon as we hit the boat... absolutely!

The worst part was that we were the most inexperienced divers (my wife and I) in a group of 7... all who were on Al80's, all who had similar gas consumption, and all who didn't think twice about reserve for their buddy.

After GD's class, and speaking with several people on this board like Lamont , DiverDown , and GD ... I'm diving 130s and my wife is diving 100's (it's all she can haul on a shore dive). MORE IMPORTANTLY, we now can PLAN our dives instead of diving by our spg. I like Lamont's advice of always being the guy who surfaces with 1000psi in a large tank.

[Tom Nic]

Ditto to everything Sounder said!

Out of the gate I purchased two HP 100's. I am not unhappy with them, but I wish now that I had bought 119's. 130's? Sounder, you da man... makes me tired just thinking about it... BUT if I had the spare Scuba Units I'd own one or two for that occasional dive when I have a reason to venture to the 120 - 130 ft. range (which is NOT that often)!

[dsteding]

The worst part was that we were the most inexperienced divers (my wife and I) in a group of 7... all who were on Al80's, all who had similar gas consumption, and all who didn't think twice about reserve for their buddy.

We are all pretty fortunate to have the resources around here to learn otherwise, and to learn it early in our dive careers. I think the vast majority of the world dives AL80s to depths where they won't have enough gas to get them and their buddy out of a bad situation. People like Bob, BDub, Lamont, and others are tireless in terms of educating divers in this area-kudos to them (sorry for not including everyone, you know who you are).

Personally, I wouldn't go past 110 feet on a single 130, that is doubles territory for me. It also just may be trimix territory-I can feel narcosis at 90, am definitely narc'd at 100, and just don't see the need to take a unclear mind much deeper than 110.

[bnboly]

After doing 2 dives with BASSMAN and seeing what his consumption was compared to mine - I have picked up a steel 130 - was all the shop had. Hopefully as time goes by my consumption will go down and I can start using 119s or 100s. I would much rather end a dive with more psi/air than the 'established minimum'!

And to quote Sounder (and others) take GD's gas management class. I took it before I was certified so mush was somewhat a mystery to me, but after diving it ALL is starting to make sense.

[jlehigh]

Thank you for making this thread so darn good folks. I'm all but a sure thing for the course on the 25th. I'll bring a few friends too

[lamont]

I like Lamont's advice of always being the guy who surfaces with 1000psi in a large tank.

Its money in the bank. With a SAC of 2.0 on the surface (two stressed divers swimming for it) you can last 20 minutes. That'll get you back to shore with a dive buddy who is OOA and with a compromised BC (or 4+ foot waves) doing the swim back at EUP...

Also:

Personally, I wouldn't go past 110 feet on a single 130, that is doubles territory for me. It also just may be trimix territory-I can feel narcosis at 90, am definitely narc'd at 100, and just don't see the need to take a unclear mind much deeper than 110.

That is about my limit as well. I also never noticed that I was narc'd at 60 fsw before I did a dive down the boundary cable in cove 2 on 30/30...

....

And speaking of the boundary cable, that is sort of "soft overhead" area due to the ferry going overhead, and that means you want to reserve more gas. You want to have enough gas for you and a buddy to swim upslope and then deco comfortably in the shallows, and it does take a few extra minutes to swim from the logs up to 40 fsw there (a better approach would be to do a direct midwater ascent to ~20-30 fsw and then swim back on a compass heading while doing an air-share, but I'd *plan* on having enough gas to swim upslope...)

If you work out the gas requirements for 2 divers at 2.0 SAC to spend 5 mins at 100 fsw then take 3 mins to ascend and do a 3 minute stop it works out to:

5 mins * 4 ata * 2.0 cuft/min = 40 cu ft
3 mins * 2.5 ata * 2.0 cuft/min = 15 cu ft
3 mins * 1.5 ata * 2.0 cut/min = 9 cu ft

40 + 15 + 9 = 64 cu ft

64 / 130 * 3500 = 1723 psi turn pressure

3500 - 1723 = 1777 psi usable

I usually use about 600 psi / 10 min at 100 fsw in a 130 (about a .55 SAC):

1777 / 600 * 10 min ~= 30 mins.

So, a 130 will give a diver, with a fairly standard (male) cold water SAC rate, 30 mins at 100 fsw with a 5 minute reserve at depth for two divers followed by an ascent from 100. That means that if your buddy has a free flow or another diver goes OOA on you, you have at least 5 minutes to sort things out while at depth, and then you still have enough gas to ascend safely and do your stops. That should cover just about anything that can happen.

On 130s I'd use 1000 psi as my rockbottom ascent time, and I'd turn the dive at 1500 psi at the I-beams or the logs -- that should give me enough gas so that I can still get 30 mins at 90-100 fsw (EAN32), even with a slightly short fill.

...

Also a lot of divers tend to plan on doing the right thing in an emergency or cutting things short. So, some would say you are recreational diving, so you only plan on having to do a 30 fpm ascent and you do stops if you have gas left over. Some plan on two divers having 1.50 SAC or 1.75 SAC. Some would plan on doing the direct ascent and then the compass swim in. Some would assume that they'll be able to act correctly in an emergency and immediately leave the bottom without wasting any gas....

I would prefer to assume it all goes horribly wrong... I'll be mugged at the pilings below the boundary cable for my long hose and my mask will get ripped off by a diver not on my team, when I get my mask back on my buddy will be dealing with the OOA victim's panicking buddy which delays leaving depth, neither of the two victim divers will be competent enough to do an open-water ascent and we'll need to swim back upslope, and one or both teams willl probably have deco time to burn off shallow...

[CaptnJack]

I would prefer to assume it all goes horribly wrong... I'll be mugged at the pilings below the boundary cable for my long hose and my mask will get ripped off by a diver not on my team, when I get my mask back on my buddy will be dealing with the OOA victim's panicking buddy which delays leaving depth, neither of the two victim divers will be competent enough to do an open-water ascent and we'll need to swim back upslope, and one or both teams willl probably have deco time to burn off shallow...

I would say this is the most likely scenario as well. I like doubles at the logs. Was down there for the first time in awhile on 32% last weekend (at night) and boy did I ever feel spacey. 30/30 is definately the right mix too.