Diving twins with manifold and isolator, but 1 reg?

[2airishuman]

Is there any way to dive a pair of aluminum 80's with a manifold such as this:

DGX Premium Dual-Outlet Manifold w/Isolator | Dive Gear Express®

but only use 1 set of regulators to breathe both tanks? Is this advisable? If not, why?

I am looking to prolong bottom time in shallow water (30-40 ft) on EAN/36 without having to dump my pair of tanks for a steel cylinder.

Well I'm not an expert but have been looking into tank configurations lately and I'll give you my $0.02 worth.

In order to convert your existing AL80s to twins you will need bands ($100) and a manifold ($100 and up). You may also need to upgrade your BC depending on what you have. Once you've done all that, if you do not need the redundancy of dual regulators, yes, you can plug one of the outlets (with a metal plug with an O-ring, not just a dust cap) of the manifold, and get more bottom time -- though without (as has been pointed out upthread) the benefits of redundant regs that manifolded doubles provide.

You may find that the pair of AL80s is "floaty" and creates trim problems.

Assembling individual tanks into a twinset, and breaking down the twinset into individual tanks, is a somewhat fiddly process that requires a flat, clean work area. It also requires purging all the air from the cylinders, which may lead some dive shops to insist on a VIP before the next fill. So unless you're going to dive the twinset all the time, you'll want additional tanks.

My advice would be to get another 1st stage and SPG, and bands, and dive the two AL80s as independent backmount doubles. That will give you the extra gas without having to re-valve your tanks and with greater flexibility to dive just one when it makes sense. Initial cost will be a little higher, depending on your taste in regs, but not much, especially when you figure that realistically you'll need a third tank if you manifold the two you have.

The only real disadvantage of independent doubles, compared to manifolded doubles, is that you lose access to half your gas in the event of a freeflow (or other reg failure). For the kind of diving you're doing, that won't matter as long as you keep the usage reasonably balanced between sides.

Another fact to consider is that even the largest steel tank will weigh substantially less than twin AL80s.

 

[PfcAJ]

I'm almost 5 9. I'm gonna demand a refund from the shop...good timing too, I think the tank is almost due for hydro

I'm 5'6''. Somehow manage double lp120s just fine.

Magic!

 

[PhatD1ver]

Possible, wouldn't advise it though, because redundancy is sweet.

As for "Ask Living Seas" as source... well... let's just say that guy seems to have a few issues with common sense and knowledge about scuba. Definitely not a good source of information, in my (not so) humble opinion.

"strapping two tanks together = sidemount" annnd.... I stopped reading and closed the tab...

 

[PhatD1ver]

Well then I suppose from an economics standpoint, if I have to rehydro both my Al80's, replace the old K valves to a manifold, and get a tech diving BC, would it not be more wise to sell the Al80's and pick up a HPS 120 if my goal is to elongate my bottom time?

Man, if you watch on ebay, there is usually someone selling L/R valves and a manifold in a set. And if you want duals, either buy a decent BPW or go sidemount (which would be my recommendation over the manifold and valves). You'll have redundant 1st stages and 2nd stages, you'll have more air available, and if you want to dive just one (monkey) you simply add an octopus to one of your LP ports and go! Easy peasy.

And there are so many more options in my opinion in this configuration now. The Xdeep Stealth 2.0 SM rig (not the Tec or Rec rigs which I think they missed the boat on) is awesome. I also have an Aquamundo that is pretty much just a recreational SM rig (just lacks that bit of buoyancy it needs for carrying a deco tank).

 

[PhatD1ver]

If your goal is to increase your bottom time, the answer is not to use a gear solution to a skills problem, the solution is to get out and dive more. Spend your weekends in the Green Latrine (Blue Lagoon) and practice. Practice your trim, practice your buoyancy, quit smoking, actually use the gym membership, get in the water and dive your tail off.

It works...

Gosh it's amazing how people can make such brash assumptions. All nice recommendations, but no guarantee to improve his SAC to the point he doesn't need the redundant air.

 

[beester]

If you are progressing into depths or runtimes needing double tanks or big single tanks, redundancy does become important. Maybe even more so if you go solo (which I gather many spearfishers do).

A double set has no redundancy if:
- You do not set it up with double regulators
- You cannot reach the valves
- You do not know how to handle valve issues.

A big single has no redundancy if:
- If you don't dive a k or Y valve with double regulators and/or cannot reach the valves.
- You do not know how to handle valve issues.

Of course in the single big tank case you can sling a pony to resolve the redundancy issue.

But in any case all options are gonna cost money. (this includes training if you don't have it). E-bay is a good option to find 2nd hand stuff... but last time I checked E-bay doesn't sell training. Whether or not you are going to invest this money is a decision on risk that only you can make.

 

[2airishuman]

If you are progressing into depths or runtimes needing double tanks or big single tanks, redundancy does become important.

I must be missing something here, but I've heard people say this before so I want to understand. How does a dive with a longer runtime inherently make redundancy important? The OP is in shallow water in the ocean and is making no-stop dives. It seems to me that a 120 minute reef bimble requires no more redundancy than a 45 minute reef bimble.

 

[Stoo]

The simple answer to the original question is yes. Slap a reg on and away you go. "Why" you would want to do that seems odd to me (and apparently others).

Assuming you have DIN valves in these tanks, I'd be inclined to plug the unused valve. If it gets opened by accident, you're going to make a lot of bubbles really fast!

 

[Imla]

The easy answer, without going into the redundancy/or not discussion is YES.
Get an Undersea Din-plug for the valve you are not using. (Make sure your plug has a release mechanism)
Keep the isolator open, and go diving.

(Of course... the better solution is to invest in an extra first stage and make use of the added redundancy as well... )

 

[rhwestfall]

or go "old school" -