How many tanks ?

[Octopusprime]

I want to start by saying I do not want this thread to become a debate over AL vs steel tanks or about training.

Currently I have 2 AL80 tanks and they have met my need. However, I'm going to start doing nitrox diving to and looking at adding stage bottles. I know to do nitrox I'm going to dedicate tanks to nitrox (under 40%). I have a plan to get to doubles with 2 stage tanks when I finish my Tec training. But want to buy smart on my way to that goal.

I was thinking of getting 2 larger tanks (110) to dedicate to nitrox will give me more bottom time on 60-90 ft dives, and in the future they could become a twin set. Then add 2 stage bottles, then add 2 more 110s convert to twins then add 2 more stage bottles.

What I was thinking...
2 AL 80 - air (already own)
2 ST 78 - nitrox stage (will need 4 for 2 dive charter)
4 ST 110 - 2 twin sets nitrox

 

[decompression]

If I may,

A very good all around set up for tanks are:

2x HP 100's (doubled)
2x al 80's (travel/stages)
2x al 40's (deco bottles)

Run a few dives on v planner or other software and see what you'll actually need for capacity. You may find the dives you do don't require 110/120/130's. The 100's are a very versatile tank for single/double and SM dives. I'm not much of a supporter of dedicated nitrox tanks if they are under 50%, as I only have so many tanks to use.


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[Octopusprime]

I guess it may matter where your diving but a tec diver I was talking to said he would rather have larger tanks than HP tanks because many OP can not fill HP or fill short. Thoughts?

 

[rongoodman]

Why bother devoting tanks to nitrox, unless you can only get partial pressure fills?

 

[Octopusprime]

So if it is banked nitrox I can go from air, to N32, N36 and back to air on the same tank?

 

[tbone1004]

if you're diving with DRiS they'll be able to pump them up, but with HP tanks of the same size just make sure you can do the dives on 3200-3300 PSI or make sure the dive shop can fill them all the way to 3600, if they can't, don't get fills there. Most compressors go to 4k minimum so it's whether or not they want to fill them up instead of can fill them up.

You need to determine your optimal tank height before you go any further. This is important because it will determine whether you buy long skinny bottles or short fat bottles for the same gas volume. HP100's are great tanks, but a bit short for me at 6'4" so I prefer 120's because they're more comfortable. Sit on a picnic table, and have someone measure from the table up to whatever vertebra is the distinct break in your neck at the top of your collar bone.

Similar to what deco said, you're better off buying used doubles already configured as doubles, in somewhat close to the size you are looking for. You'll likely have to drive a bit, but it'll be worth it.

My current configuration
Double LP72's *perfect for recreational type diving or teaching. Gets me out of singles and has about the same amount of gas as the guys with pumped up 108/112's or 130's, works well
Double HP120's *preferred deep ocean/technical diving tanks
Sidemount 120's *same as above just for caves
LP72's x4 sidemount open water bottles, mainly for shallow caves or if people want to borrow them
AL80's, x4 for stage/travel gas, usually only use 2 max, but have the others for people to borrow
LP72 O2 deco *cave or if I'm dropping it off
AL30 O2 deco *if I'm carrying it

Change the steels to whatever you want or can find, doesn't really matter what they are, but buying used doubles is infinitely cheaper than buying new ones. Re. nitrox, unless your shop is partial pressure blending, which is such a horrible way to fill and actually would cause me to look for another fill station for nitrox *seriously*, then there is no reason to dedicate tanks to air or nitrox. If the shop is continuous blending and banking air/nitrox which the good ones should be, then the only difference in the gas is whether the O2 valve to the stick was open or closed, same compressor, same filters. Only tank that gets an O2 clean sticker *they're all O2 clean, just don't put that sticker on there*, and the only one that doesn't see all gasses is my O2 bottle, everything else gets whatever put into them and just analyzed at the end of the fill. Too much effort to dedicate bottles to air or nitrox. You can't go from Air to 32 to 36 without dumping the whole tank, but you can certainly top off with whatever other mix you are diving, usually just means an extra minute of deco or two depending on how empty the bottles were. I had air in my bottles at the start of the cave trip last weekend and they just kept getting topped off with 32% all weekend, just have to analyze and adjust the computer accordingly

 

[rongoodman]

So if it is banked nitrox I can go from air, to N32, N36 and back to air on the same tank?

Certainly. Just be sure to analyze and label them.

(That being said, I've quit doing business with a local dive shop who insisted on having bumper sticker Nitrox labels on the tank before they would fill it with banked nitrox. You never can tell what kind of stupidity you might run into.)

 

[decompression]

I guess it may matter where your diving but a tec diver I was talking to said he would rather have larger tanks than HP tanks because many OP can not fill HP or fill short. Thoughts?

Good point, check your LDS and see. If your travelling with your tanks then check the areas you go to. I'm getting older and my long deep dives are getting fewer so the requirement for 130's isn't there. But again to see what you'll need run some profiles.


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[tbone1004]

Ron, nice thing with cave country is half the time they don't bother checking for VIP stickers because they know that especially in sidemount they tend to get rubbed off or live under the cam bands. "are your tanks in VIP?, cool", they tend to check hydro but certainly goofy requirement for damned nitrox stickers. Small piece of painters tape is all they get with the mix on it.

 

[Jared0425]

I've started to use LP Faber 85's for deep dives in the 170-200 range and I have more than enough. I like them more than the my doubled Faber 100s and PST 100's. Plus I pump them up to 3200 also.