Is this a good deal/choice for a set of doubles?

[tbone1004]

there is a knob in there, just rotated backwards. tanks are probably empty.

also, I'd argue that the main benefit of doubles is being able to access gas from both tanks from a single regulator as isolation is an extraordinarily rare event. If you think the main benefit of doubles is the ability to separate them, just dive independent doubles *which I do...*

 

[CuzzA]

Thanks. It appears it is facing back. I'm going to call the guy now and get more details. I'll report back for your guys feedback before parting with my money.

 

[Stoo]

also, I'd argue that the main benefit of doubles is being able to access gas from both tanks from a single regulator as isolation is an extraordinarily rare event. If you think the main benefit of doubles is the ability to separate them, just dive independent doubles *which I do...*

Perhaps where you dive, needing to isolate is rare, but diving in water that is hovering just above freezing for half of the year, being able to isolate both the tanks and the regs is critical.

But I agree, than in many situations, independents would work, and that's the reason that sidemount has become very popular up here.

 

[tbone1004]

Perhaps where you dive, needing to isolate is rare, but diving in water that is hovering just above freezing for half of the year, being able to isolate both the tanks and the regs is critical.

But I agree, than in many situations, independents would work, and that's the reason that sidemount has become very popular up here.

what? why would you isolate? You only isolate if you have a valve problem, i.e. busted o-ring on the crossbar or the neck, a bad burst disc, for some reason the valve itself has frozen where you can't turn the valve, or the extraordinarily and unheard of to me event of a regulator freeflow where for some reason the valve won't shut down because the seat has failed. If you have to shut down that often, you need better regulators or technique in ice diving. Yes I've done it, no it's not that difficult if you behave and rotate second stages somewhat frequently so you don't have ice buildup, but isolating shouldn't have anything to do with whether the regs are frozen or not.

 

[Stoo]

All of which are possibilities... admittedly rare. Having said that, the one time a buddy (my ex) found herself without gas at depth was when an o-ring disintegrated in a rental tank, so while it may be rare, valve failure's are possible...

There are tons of threads here debating the merits of various tank configurations, so I think there's much point in derailing this thread. My only point was that to me, the isolator is an important feature and I'd keep looking for another set of tanks. I bought my first set of doubles in 1977 I think... twin 72s with a single centre outlet...

 

[Caveeagle]

Other nice thing about these for your ART class is they are going to save you a bunch of money on helium since they're small tanks and you don't have to fill the big ones all the way up for class

Great point. I did not consider the cost of gas for training.

 

[tbone1004]

All of which are possibilities... admittedly rare. Having said that, the one time a buddy (my ex) found herself without gas at depth was when an o-ring disintegrated in a rental tank, so while it may be rare, valve failure's are possible...

There are tons of threads here debating the merits of various tank configurations, so I think there's much point in derailing this thread. My only point was that to me, the isolator is an important feature and I'd keep looking for another set of tanks. I bought my first set of doubles in 1977 I think... twin 72s with a single centre outlet...

i wasn't debating merits of having a non-isolating manifold, I think those are scary, just that isolation itself is an extremely rare event and if you're seeing instances of having to isolate regularly than I would just remove the crossbar altogether and dive independent doubles which is what I do most of the time.

@Caveeagle you still have to breathe the same amount of gas during training, that doesn't change, but it's a lot less wasted gas when you have to dump it for VIP/Hydro/mix changes

 

[2airishuman]

Tomorrow I plan on buying my first set of doubles and want to hear if you guys think this is a good deal. I will use these for my Advanced Rec Trimix class and I'm thinking they could also become deco bottles in the future.

2x Steel 72's Recent Hydro and VIP.
DiveRite isolation manifold with DIN valves.
2x Bands.

$150

Price is so right it's hard to find any reason not to. Even if you figured the cylinders themselves are worth nothing, the hydro VIP valves crossbar and bands come to more than $150.

Some caveats to consider
- LP72s are widely considered to be too small for trimix diving, due to rule of thirds and rapid use of gas at depth. If they work for you, great, at that price, maybe they're worth it if you just use them for the class.. but.. in the long run, you may want to look at larger cylinders
- Gas to weight ratio with these isn't the greatest. Two LP72s weigh considerably more than an HP120 and an AL19 for essentially the same amount of gas, for example.
- LP72s require special bands, so you won't be able to use those bands with larger cylinders in future.

Ideally that would be a 200 (232? whatever) bar manifold. The older 300 bar manifolds are just a nuisance because most places have to find an adapter to fill them and you can't use them with any yoke regulators you may have.

 

[scubafanatic]

Maybe an obvious question but, did you run the potential purchase by your class instructor ? The 'tech diving' world is much more particular about gear types/styles/capacities than the recreational dive world. Has the instructor approved this purchase as 'suitable' for the class/circumstances ? I'm also assuming the instructor isn't/won't be upset you didn't buy some new tanks from him/her. (I have taken tech classes where I'm pretty sure part of the deal was buying a bunch of shiny new gear at full retail pricing from the instructor.)

I own a pair of Faber LP steel 'doubles'....(LP 85's and LP 76's.....both sets '+ plus' rated for 2640 psi) . I think a pair of 72's would be too small to be all that useful for 'tech' diving. I have slight experience (through classes and a cave diving class in Akumal, MX) with 'double LP 95's and 'double' AL 80's....and I'll agree that's already as much or more weight I want to try to deal with on land, so my hat's off to those dealing with those uber large steel 'doubles'!

The 'tech' dive shops are really pushing 'sidemount' these days as well....another revenue stream to get folks to scrap their 'old' backmount gear.....so you may want to double check with your instructor about that.

Don't fall into the trap of buying something just because it looks like a good deal, unless you plan to 'flip' them on EBay or something. Tanks are more of a pain to 'flip' anyway....shipping being costly/expensive, which is why so many tank sellers sell under 'local pickup only' conditions. If it's really for your own use, make sure it's will actually really be useful for YOU.

 

[tbone1004]

@2airishuman rule of thirds is only applicable in penetration diving, it is not applicable in open water technical diving do to there being nowhere to "go". 72's are perfectly fine in size for this type of diving, especially the course in question which is ART where the depth is limited to something like 150ft. Good for well over half an hour at that depth with a good SAC rate and you are going to be limited by the deco limits of the class.

The bands in question are not the special bands, they are the same ones that are used for LP85's which are quite common.

If the instructor wants him in doubles, a set of double 72's vs a HP120/al19 isn't going to work, and an AL19 is grossly insufficient for a pony bottle at those depths *they're also only about 5lbs heavier than a HP120 and an AL19 btw*. Gas to weight is only not as ideal if you consider no overfill. May if not most of us that still dive LP72's have no problem taking them to 3000psi where they hold about 87cf per bottle and up at those pressures they have some of the best gas/weight ratios out there. I'm not sure if IANTD requires doubles for this course or not

WRT the manifold. He is taking a technical diving class. DIN regulators will be required regardless of a requirement for doubles or not.
DGX Premium DIN Fill Adapter | Dive Gear Express®
DIN fill adapters are $20, if you own DIN tanks, you should own one of these, regardless of if it is 200 or 300 bar because it is much more convenient than spinning yoke inserts into and out of the 200 bar valves.