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

[halocline]

Those are galvanized tank, and they do look like LP72s. The easiest way to check is to look for 3AA 2250 on the stamps. That means they're 3AA spec, which is a very proven and conservative design, and the working pressure is 2250 PSI. If they are PST tanks, there is a document floating around the net (check vdh) that lists the REE number for those tanks. With that almost any hydro facility can give them the + rating they need to bring them to 72cft at 2475 PSI.

I would not be worried about the fact that they don't precisely match.

Double LP72s are not my favorite doubles, although lots of people like them. They are my favorite single tanks. For whatever reason they trim out better for me as single tanks. I have three of them, I used to have two of them as doubled, but I eventually broke them up and used the bands/manifold for AL80s. Ironically, to me AL80 doubles are better, but I don't like them as single tanks. Go figure.

Most dive shops will fill them with no problem. They're extremely proven, reliable tanks. Hydro shops are a different story; first, if they are lined, many hydro shops won't touch them, and many hydro shops simply won't give any tanks the plus rating (unless the REE number is stamped on the side, and even then some hydro shops around here just won't stamp them). Thank god you only have to go through the hydro shop idiocy once every five years.

If the bands and manifold are in good shape, $150 is not a bad price just for those items. If the tanks are in decent shape, $150 is also a good price for those alone. So $150 for everything is really cheap.

What I would do is ask to look inside the tanks. If they're plastic lined, I'd probably offer a little less (maybe $100) for just the bands/manifold. If they're not lined and there is no obvious corrosion in the tanks, I'd buy them right away. It's not difficult to look inside the tanks, you just need a light that will fit down into the neck of the tank. LED christmas lights are perfect.

 

[2airishuman]

@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.

Ok, you know more about this than I do. Nonetheless, I'm not sure how useful twin 72s would be after 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.

The point was that they don't fit the larger 7.25" and 8" diameter cylinders that are more typically used for twinsets. HP100, 117, 120; LP95 and up.

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

Most of that's true (I get a 10 pound difference in weights, but whatever). I don't think my original post was very clear.

The point I was trying to make is that, unless upfront cost is the main factor, there are generally better choices for most dives than LP72 manifolded twins. If the goal is simply more gas at recreational depths, a larger single either with or without a suitable pony is a better choice -- lighter, simpler, cheaper to fill. For a dive where the redundancy of a twinset is necessary, most divers would choose something larger.

WRT the manifold. He is taking a technical diving class. DIN regulators will be required regardless of a requirement for doubles or not.

Right, but, maybe he'll want to use them with other regulators too.

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.

I have one, yes. I don't always have it with me, and I don't like to leave it at dive shops when I get fills.

 

[guruboy]

The price is right if it has recent hydro and vip. Buy the tanks and worst case you can probably sell them for $100 each and end up with free bands and a manifold.

As for the isolator, just make sure it can spin freely by hand. It's position in the photo isn't something worth worrying or speculating about. Maybe that's where the guy liked his. I dive with mine pointed back away from my head.

If this was in my area, I probably would have gone and bought them already while all this talk was happening.

 

[CuzzA]

The seller said the tanks are rated at 2600??? Maybe he meant 2400.

He has all the hardware and they are put together, just not in the photo.

Tanks are full and he preferred the isolation valve pointed back.

He didn't know what I was talking about when I asked about plastic lining, never heard of it. Probably a good thing because if they were I'm sure he would know.

I think I'm going to buy them. I don't see how I could lose even if I sold them down the road.

 

[Caveeagle]

As guruboy stated... If they were nearby to me.. I would have already bought them. Your intended use is the only thing questionable.

 

[CuzzA]

Your intended use is the only thing questionable.

And with that statement I decided to pass. The more I thought about it and while they may make a great set for certain dives, I think they'll spend more time collecting dust.

So, let me pick your guys brain.

My ultimate goal is to play in the low to mid 200' range from time to time. While I know closed circuit would make more sense long term considering the cost of helium, the initial upfront cost is not in the cards at the moment.

So doubles it is. After doing a little more reading I'm leaning toward LP85's. Filled to 3500 would give me 112 ft3 per tank. 224 total. And I'm assuming a couple AL40's will be part of the plan too. My diving will almost always be in the ocean from a boat. Also, I'm going to be BP/W shopping. I'm leaning toward Kydex or aluminum. Diving 112's in a full 3 mil suit I do not wear any weight. So what do you guys think?

I'm sure there's a billion threads, maybe you can point me in the right direction or maybe there's some new info that should be considered. Or maybe some better options other than the LP85's.

 

[lowviz]

...//... My ultimate goal is to play in the low to mid 200' range from time to time. ...

You passed on a set of tanks, bands, and a manifold that will take you into hard deco for $150???

(IMHO) Your overall dive planning needs a bit of work...

 

[CuzzA]

Well, I'll be honest, I'm ignorant to doubles. I see a few used options out there, like double 85's for $400. Double 112's for $500.

My thinking is those 72's are going to get very little use going forward. So while I agree it's a great deal, it appears that most used sets being sold are basically throwing the bands and manifold at no cost. I see the same tanks being sold individually for $200-$250.

So I buy this set, move on to something with a higher capacity and sell the tanks for what I paid, but I'm still buying individual tanks at $200-$250. Am I going to carry those 72's for the diving I intend on doing? Seems like AL40's make more sense. I'm not setting stages. And if I go to a bigger tank the bands and manifold are useless to me, right? So where am I saving?

Honestly, I need a set of doubles. I saw that offer and wanted to get your guys feedback. I posted before doing a lot of research in the hopes of jumping on the deal if it made sense. But I'm not sure it does. And I'm not the type to just flip gear. I want to buy the gear I will use.

If I'm wrong, set me straight. That's why I asked.

 

[tbone1004]

if you're leaning towards LP85's you just passed on a set of bands and manifold that would have worked for those tanks.... For ART, I would have bought them, used them for class and being a forced limitation on your dive time at this point, but giving you sufficient bottom time and redunancy. That said, the 85's aren't significantly bigger. Cave filled they hold 115cf, vs 87cf for the 72's at 3000psi. 56cf is only good for maybe 10 extra minutes at depth, not significant enough of an improvement to justify. They're in hydro, in VIP, use them for your class, and if you don't like them, flip them, no way you're going to lose money on them.

When you want to start doing the bigger dives, the 112's that you have are going to be a meaningful improvement in gas, giving you almost double the volume of the 72's, but at this point the 72's if you can get them filled to even 2800psi are going to give you 160cf of gas. At ART limits of call it 6ata, a SAC rate of 0.6cfm, and using rock bottom, they'll give you 20 ish minutes at depth. That's quite a bit of bottom time and that depth is going beyond what that cert level is going to give you.

 

[2airishuman]

Well, I'll be honest, I'm ignorant to doubles. I see a few used options out there, like double 85's for $400. Double 112's for $500.

Think about the dives you want to do and how much gas you will need using an honest estimation of your SAC rate. I know from your other posts that you like long dives.

Some data points to consider.

I find that HP100 doubles are the largest that I can comfortably handle overall -- shore entries and exits, stairs, getting them in and out of the trunk of the car for air fills, and the like. I had a 120 twinset and ended up splitting it because it was just -- barely -- more than I could manage. Handling it in and out of the car was the killer more so than the dives themselves. So I dive a pair of HP100s. I could still dive 120s or larger if I had a dive that absolutely required it but then I would be in a situation where I would need help handling the cylinders or would have to be more careful about my choice of dive support vehicle and use a cart or two wheeler or something.

HP 100 doubles are around 90 pounds with air, bands, and manifold.

With the HP100s gas is still limiting for me down to around 60 feet unless the profile is truly square. I haven't been diving nitrox but if I were gas would be limiting to around 90 feet assuming a typical shore diving profile. But I can get a good long dive that makes the surface swim worth it.

A fact to consider is that you may at some point dive in a location where cave fills are not readily available.

Bottom line you have to look at your SAC, what you can handle weight wise, and the dives you want to do.