Tank Advice - First Time Buying

[ScubaSpicher]

For those that dive 130's... have you ever doubled them up? Also, if you do not mind me asking how tall / big are you? I am sure they trim nice, but I would rather not go excessive if smaller tanks will fulfill my needs. Thanks again everyone for helping me figure this out!

 

[rcpilot44]

I am 6 ft and 300#s. I largest tanks that I have personally seen doubled up are 119s.

 

[ronbeau]

I agree with Little John on the hp100's.You can have a lot more gas with bigger lp's but some shops wont overfill them.The hp's are stamped 3400 psi.

I believe the working pressure HPs is 3442.

 

[Colliam7]

For those that dive 130's... have you ever doubled them up? Also, if you do not mind me asking how tall / big are you? I am sure they trim nice, but I would rather not go excessive if smaller tanks will fulfill my needs.

5' 10.5", 200lbs. Double 130s are great to dive. But, I also dive and like double 120s, double 100s, and double 80s. I also dive double 119s (borrowed), but I like them the least of the 5 sets, mainly because they are so 'dense', and I find them more awkward to move around on land. 130s are heavier and longer than 100s, but both are very nice tanks.

 

[scubaskipper]

HP-100, best all around for single or double. We don't all have the cash for a different tank for each type of dive we do. If a shop or boat can't fill a HP tank, go to a better shop or boat, something newer than 30 years old. SAC rate concern? Get in better shape, stop smoking, dive more, cut out the booze, eat better and get more sleep. Smaller, lighter tanks take less to move around. Just an observation from watching many of the people with the bigger tanks. Just my 2 cents.

 

[TSandM]

My regular dive buddy dives doubled HP130s. He's about 6 feet and moves diesel engines for a living. A full set of 130s is a serious amount of mass!

Double HP100s are lovely tanks -- They trim out well, are light enough to manhandle on the surface, make it a little easier to keep your balance on a moving boat (compared with more massive tanks) and hold enough gas for dives in the Tech 1 range.

 

[Puffer Fish]

Thanks for the replies everyone! So a couple more comments / questions. I'll assume for now, since most of my diving is done helping classes, that for the single tanks I use do not have to be very large since most people will have higher SAC rates. On the other hand as I begin to switch over to tech I believe most people that I dive with... in the beginning will have lower rates, so I would want slightly larger tanks.

Anyway... have you ever experienced shops that are not able to fill a HP tank to stated pressure? I have heard arguments that it happens, but do not think any shops I have seen would have that issue.

Also, is there a reason you are all suggesting tanks with 7.25in diameter and not the larger 8in diameter tanks?

Lastly, have any of you dove with the 120's that are 7in in diameter? I would not want a tank that hits my legs or head, but being 6'3" would they be too long?

Thanks again!

As you can see from the responses... what is best varies by the person.

Regarding fills.. yup, I have had places that cannot do exactly 3442...however.... a HP steel 100, filled to just 3.000 still has 87 cf of gas, which is more than an aluminum 80 has (which is not 80 cf ft, by the way). If you ignore the maximum capacity for a minute.. with a worthington x7-100 versus a Al 80, both filled to the same 3,000... you will be carrying roughly 5 lbs less and have 12% more gas...not bad.. (87 versus 77.4).. anything over that is just extra nice.

Regarding diameter... spectrum's statements are spot on...

So why do I have both? Well I got a tremendous deal...price won out over ideal size.

Your comments about air usage changing as you dive and who you dive with are right on also.

My air usage on a normal dive is right around .42 cf/min (surface rate). That is way lower than most new divers, and way higher than most experienced women or small people...if yours is around that number, I would get 120's..

Note: With Worthington X7-120's.. you are roughly one pound heaver than an al 80.. with 2 lbs of extra air weight.

If you have a very low rate for a big guy...then 100's would be nice. Otherwise, I would suggest 120's

One other thing...these should be nitrox/O2 clean tanks. Unless one is doing deco dives, it is easy run out of bottom time with air and a large tank...with my 117's, if I use 27 cf as safey air, I have:

Surface: 214 minutes

33 ft: 107

66 ft: 71

99 ft: 53.5

Not the sort of natural safety factor one has with the Al 80. Diving with students, it would not matter. Diving with experienced divers... it does.

 

[TSandM]

That is way lower than most new divers, and way higher than most experienced women or small people.

Really? My cold water SAC rate is about .4, and is considerably lower than that of anyone else with whom I dive. In warm water, single tank diving, I can get down into the mid .3's, but never lower than that -- I'd have to skip breathe.

 

[Puffer Fish]

Really? My cold water SAC rate is about .4, and is considerably lower than that of anyone else with whom I dive. In warm water, single tank diving, I can get down into the mid .3's, but never lower than that -- I'd have to skip breathe.

Dive with Marvel or Scuba Jenny... I don't think either of them are higher than .25, and they might be lower (Jenny for sure).

Even .35 versus my .42 is the same difference as 100 versus 120.

Oh, and you are so bad for even bringing up skip breathing..

I went back and looked at some of my cold water dives... boy can I suck air when I first hit the water...but after that, I'm back to about the same as warm water.

 

[pescador775]

Your choice seems to be single 130 or double 100. The doubles are more versatile for implementing a tech diving philosophy. They allow all kinds of backups, hookups and are more stable than a single, large tank. No pony tank needed. Don't go crazy with the cubic footage.

I used to dive with a guy who was the same size as me and used the same type of gear. In the water, he showed a tendency to float feet up. He eventually bought ankle weights. If you are one of these folks then there is cause to worry. Otherwise, trim is a non issue regardless of tank length.