Double HP 120's

[Northeastwrecks]

Hello Everyone.

I am upgrading my existing rig from a Halcyon Pioneer 36 to an Explorer 55.

I currently own two HP 120's that I use as singles with the Pioneer. I am considering doubling them for use with the Explorer.

I could purchase two LP 104's; however, I wanted your opinions on the 120's before I spent the money.

I am large enough (6' 3", 250 lbs) to carry either in relative comfort.

I dive in a drysuit.

I understand that I will need to install proper valves, manifold, etc...

Thanks for your help and advice.

[sheck33]

personally i prefer the LP 104's, they are easier to fill and you get relatively more air for the same overfill as compared to a HP 102 or HP 120. I have gotten away from HP tanks alltogether.
Then again you already have the two HP 120's.
If i were you i'd buy two LP 104's and double them up, you wont regret it.

[Spectre]

What sort of questions are you looking for answers with? I do know people that dive double 120s without issue. I'm assuming you'd be looking at PST LP104s. What are the HP 120s, PST? From what I can tell, the PST LP104s are a little bigger [but shorter] and heavier. They are about a # heavier full and 2 #s heavier empty [so you'd drop a little weight]. So the 120s'll be lighter in the water, on your back, and you already own them! :)

[edited brain-fart out]

[Northeastwrecks]

Spectre once bubbled...
What sort of questions are you looking for answers with?

I guess my primary issues relate to buoyancy, weight issues and whether there is a benefit to the LP tanks that justifies the additional expense of buying them.

[Spectre]

Northeastwrecks once bubbled...


I guess my primary issues relate to buoyancy, weight issues and whether there is a benefit to the LP tanks that justifies the additional expense of buying them.

Hmm... well, we should definately be able to find the specifications of the tanks you currently have, and then do some calculations based on the differences between the two tanks.

If you're talking PST HP120s vs PST LP104s, it's really nominal... 120 empty is -1.3, 104 empty is -3.3. So your net weight goes down -5.3 w/ LP104s. PST HP120s would just be another -1.3 off. So you'd be able to take off about 4 lbs more ballast with the 104s over the 120s. [if I'm not forgetting something]

[edited to add something I forgot]....

Oh. Above water the LP104s'll weigh about 14 lbs more than the doubled 120s

[detroit diver]

The balance and trim when using the 104's has been proven by usage. I don't know how the 120's would balance out, but as someone previously said-you own 'em. Try them out, and if it doesn't work, put them up on Ebay. I bet you'll get close to what you paid for them-enough for a set of 104's!!

I've got a set of lp95's going up for this very reason.

[Uncle Pug]

I suggest that you go with the LP tanks for doubles since with that much gas you are going to be diving either nitrox shallow or mix deeper... so blending becomes an issue... unless you have a booster you will giving more gas back to the supplier and even with continuous blending it makes more sense to use the LP tanks.

But if you can get the kind of mix fills that you want with the HP tanks then all the above is of no consequence.

[Scuba446]

That leads me to another question - most of my LDS' don't even do Trimix fills. Where is one supposed to get these Trimix fills done? Yourself?

[JamieZ]

In your area,,,,((((Make Your Own))) or All About Scuba,,,Northern Tech Diver,,,,,Limestone Dive Shop... By the time you get your Trimix certification you should be doing enough dives to justify making your own fill station. Unless you can get fills cheap enough where it wouldnt make sense to make your own.

[trheeltek]

Disclaimier: I love my 104s, so I might be biased

I think the stuff folks have written is pretty valuable, especially regarding the proven weight distribution of double 104s. I looked at a similar decision, and here are the three biggest reasons I got and doubled the 104s is:

1 - Lots of folks dive them, so I knew they worked great (which they do). I've heard concerns over correct trim with HP tanks.
2 - With an overfill, I can get more gas than I could with HP 120s (which shouldn't be overfilled).
3 - I still do some coastal diving where I don't need or want doubles, just a high-capacity single with an H and a stage bottle. The 120s work great for that. If you don't expect to dive singles anymore, not a concern for you.

You will never regret buying the 104s, IMHO. If you do, you can resell them pretty easy.

[Northeastwrecks]

Thank you for all of your advice. Based on your comments, I intend to order the 104's in the near future.

I will keep the 120's because I may still want to dive singles on shallower dives, when shore diving or when working with students. Besides, I'll still have the Pioneer wing, so it seems silly to give up the tanks.