New tank buyer questions

[twistypencil]

I'm assuming you know your RMV. Ideally, how much gas would you need to optimally execute your usual dives? That would logically dictate the best cylinder size for you.

The fatties, 117 and 133, are both shorter than a 120. A 133 weighs a little over 3 lbs more than a 120

My median SAC is 16-18l/min, the mean is 18-20l/min. My average dives are between 40-50 minutes, usually air is the limiting factor.

 

[rx7diver]

My median SAC is 16-18l/min, the mean is 18-20l/min. My average dives are between 40-50 minutes, usually air is the limiting factor.

@twistypencil,

Are you buddy diving doing recreational dives? If so, then what cylinders do your buddies tend to dive?

rx7diver

 

[twistypencil]

@twistypencil,

Are you buddy diving doing recreational dives? If so, then what cylinders do your buddies tend to dive?

rx7diver

Yes, I usually go with other divers, they usually are using HP100 steel, but I'm consuming air faster than they are

 

[crofrog]

hp120 or hp100 is what you want. The 133s are just heavy

Tell that to my wife and all the women in FL carrying around double 130s

1. I have an outdoor, unheated garage space, can I store the tanks in there, or is that risky?

That's fine. Store them vertically.

2. I'm wanting steel, as I prefer the bouyancy

I know people say this all the time, but it's really "how much of the tank's weight contributes to my total weighting." A AL80 finishes a few lb positive when completely empty so you need to add a few lb to your rig to compensate. 133's finish about 1lb positive, 100s and 120s depends on the tank but most are around -1lb negative. So it's really not a huge difference.

3. I understand I should not buy used tanks without hydro

If you're buying used out of hydro tanks, try to deal with people who say they'll give you the money back if they fail hydro or will get them hydros first, and let them know you'll pay for the hydro if they pass. I've found the northeast scuba community pretty honest, and these steel tanks don't fail hydro very often and most of the ones that do look destroyed.

5. I use more air than everyone else
6. HP120 or HP133 seem like what others around my height/weight are recommending here on the forum. Does that match up with dry suit and steel BP/W?

How much lift does your wing have? With those bigger tanks, the wing might not have enough lift to float the rig without you in it, which you want to avoid. 30lb should be enough for most of them, though.

Yes, 120 or 133's is fine with a drysuit and a steel plate for most people. If you're diving in very thin undergarments, you might find yourself a bit overweighted if that's the case, an AL plate is pretty cheap

7. Can I avoid LDS markup by doing hydro/VIP at a fire extinguisher place? I'm wanting to do the math to see how it all works out, and want to call some local shops. It costs me $30/tank/day for steel right now
8. It seems scuba.com has faber hp133 for about $400, DGX for $534... I usually find DGX to be a better price, why is that price so much higher?

The fabers I see at scuba.com are not hot dip galvanized. You want an HDG tank they hold up much better than the painted ones.

 

[lexvil]

HP 100 vs HP 120

 

[scubadada]

My median SAC is 16-18l/min, the mean is 18-20l/min. My average dives are between 40-50 minutes, usually air is the limiting factor.

So, your gas consumption is a little more than the overall average

Average Gas Consumption

Although I think this thread provides some interesting scientific discussion, I haven't seen the practical value clearly drawn out for Basic OW divers. It seems like we've become overly fixated on compiling data without extrapolating and consolidating some useful conclusions. Call me crazy but...

scubaboard.com

Use your RMV and your average depth, along with your desired dive time, to calculate your gas requirement. For instance, you would need a little over 80 cu ft to do a 45 min dive at an average depth of 60 ft. That would require at least a HP100.

What cylinder are you currently using that limits your dive time to 40-50 minutes? What are your usual average depths?

 

[twistypencil]

How much lift does your wing have? With those bigger tanks, the wing might not have enough lift to float the rig without you in it, which you want to avoid. 30lb should be enough for most of them, though.

I'm actually uncertain how to answer that question. I have a Hog harness, Hog 32lb 360 Bungee Wing, Dive Rite Backplate Stainless Steel, which is about 6.9lbs. When you ask about lift, are you talking about the 32lbs that wing is rated at?

Yes, 120 or 133's is fine with a drysuit and a steel plate for most people. If you're diving in very thin undergarments, you might find yourself a bit overweighted if that's the case, an AL plate is pretty cheap

I've been using lead weights so far, hoping to reduce that.

The fabers I see at scuba.com are not hot dip galvanized. You want an HDG tank they hold up much better than the painted ones.

Thanks for the tip!

 

[twistypencil]

HP 100 vs HP 120
View attachment 868249

Which is which?

 

[twistypencil]

Use your RMV and your average depth, along with your desired dive time, to calculate your gas requirement. For instance, you would need a little over 80 cu ft to do a 45 min dive at an average depth of 60 ft. That would require at least a HP100.

What cylinder are you currently using that limits your dive time to 40-50 minutes? What are your usual average depths?

Well, the problem is I am using different cylinders and I've just switched to dry, and am still sorting out my weight. So its hard to really match the data up. For example, last weekend I had an average depth of 24.27feet, 57minute dive with 1310psi remaining, that was using an HP100, first time I stayed dry in my suit, and I was overweighted (22lbs lead on a belt, plus steel backplate). In this situation, air was not my limiting factor. The week before I did average depth of 22.3feet, 58 minutes, with 314psi remaining on an HP100,same weighting, but the zipper wasn't closed, so I flooded and was cold.

When I dove in Cocos where the average temp was 24-26 degrees celsius (75-78F) with a 3mm suit, Nitrox on an AL100, I averaged 57 feet, average of 707psi remaining, with a duration of 45-50 minutes

 

[twistypencil]

Who typically pays for the hydro on tanks that are out of hydro, but have a guarantee?