Should I go for dual tanks?

[Citycat]

I know a lot of people have asked this question before, but I would just like some advice on the subject of dual tanks. I am a Master Scuba diver, with over 100 dives on my belt. And I have lately been looking into getting a dual set up. Some of the reasons that I am concerned is just the weight factor, and the actual expense. I am 5'8 and 130lbs. I dive a dry suit with 24lbs and a steel 100. Most of my dives are 40-60 min and a range of 1300-1600psi left over. I was wondering if it would be beneficial at all to purchase a dual set, or to stick with my singe.

 

[masterof0]

Unless you are looking to get into deco diving, overhead environments, deep, or high risk environments where you need full redundancy, there is not a compelling reason to go doubles. Based on what I am taking away from what I am reading here, a single tank is offering you ample air for your dives. So, going to doubles will gain you redundancy, but not much else.

 

[Scared Silly]

What problem are you trying to solve with doubles? For the sounds it coming back with nearly 1/2 of cylinder of gas after 40-60 min means you are not a hover. If you want to get some lead off your belt there are some other cylinders made by Faber 3180+10% that are very negative.

 

[Citycat]

What problem are you trying to solve with doubles? For the sounds it coming back with nearly 1/2 of cylinder of gas after 40-60 min means you are not a hover. If you want to get some lead off your belt there are some other cylinders made by Faber 3180+10% that are very negative.

one of the reasons why I've been looking into it is to increase my dive time. I'm into underwater photography and it would be nice to be able to increase my time in order to get more pictures.

 

[b1gcountry]

If you're coming back with 1300-1600 psi left, then I would say you can extend your dives with the current tanks, with no problems. Also, living up where you do, there is also the chance that more air might not help you if you're going to get cold after 60+ minutes anyway. You might wind up with more than you bargained for if you go to doubles to extend your times, and wind up getting all sort of other gear to make you warmer too

I think a lot of people go for doubles because they are kinda neat, and because they are gear heads. It is fun to set them up, and learn how to use them. It also gives you an excuse to buy all kinds of new gear whether you want to or not. It's also kind of nice to be able to do two or three dives on one set of tanks and not have to worry about changing out tanks in the cold weather. It helps me in the winter to give my hands a chance to warm back up between dives because I'm not messing with my regs between dives. My wife has also come to like the improved balance you get in doubles-especially AL- over her HP130s. They don't roll on her as easily as the heavy single tank does.

I guess my point is you can probably extend you bottom time other ways if that's really your main goal...but if you just want to set up a set of doubles for the heck of it, there's that option as well. Just realize what you're getting yourself into. Steel doubles can run between $600-1000. Add on top of that another first stage, probably more hoses, a new wing, and possibly a BP if you didn't have one of those. After doing that for a while, you'll get tired of swapping your doubles/singles regs around, and will opt for a whole separate set of regulators for singles and doubles. Add in a class or two like Fundies or Intro to Tech, and you are up in the $2-3K range just to extend a little bottom time.

If you think that is an exaggeration, it isn't. I started out cheap with some tanks I had, and a spare reg. I bought a used wing for $75, and a used sherwood first stage for $50. Bands and manifold were another $250 or so. Since then, I've replaced the steel singles, bought a nicer wing, spent around $2500 in classes alone, replaced my regs with Scubapros, I now own four BPs, and on top of it all, my wife has decided she likes doubles, so now I get to do it all over again.

Anyway, just be sure you know what you're getting into

Tom

 

[mkutyna]

I don't think it would be a problem to extend your dive time on your current tank as long as you aren't doing deep dives. I don't think we're suggesting that you extend your dive time to the point that you arrive at the surface exactly at 500 psi but bringing your threshold to around 1000 psi wouldn't be too bad and can give you a decent extension of time underwater.

One possible alternative to doubles is to sling a stage bottle. Perhaps a 40 cu ft bottle. You would have to be careful about how you use it though. For instance, breathe off the stage bottle first until you get to around 2000 psi, then switch to your main cylinder until it is around 1500 psi then switch back to your stage bottle for the rest of the dive. Stage bottles are a different type of bulk to move around with so I'd suggest renting a pair of doubles and/or a stage bottle to see how you like them before purchasing either.

 

[Trimix2dive]

if you want duals give them a try. trim better.....etc. or just because you want them.

 

[jay knapps]

one of the things you need to remember about you having the only set of twins on that dive. it may be you are adding more bottom time,and adding more time for photos.but what about your buddy ? they will become the controlling factor in this dive problem anyway, and you should never dive alone. but as with any dive that takes your eyes off your gauges or computer it is important that you and your buddy are on the same page with your air usage.just food for thought before you send the extra bucks,that you might be used on a cool dive vac. or other equipment you would get more out of.

 

[TSandM]

If all you want is more gas, buy a couple of HP130s. They trim out great and hold as much gas as a small set of doubles.

If you are looking at deeper dives or decompression, doubles are ideal because they afford redundancy. But they do it at the cost of increased complexity and significantly increased cost. Not only do you have to purchase bands and a manifold, but you need two first stages. In addition, every time you take them to the dive shop to fill, you pay twice as much as for a single tank. (Unless you belong to something like NWSD's Executive Aquaholics membership )

I dive doubles here in the Sound for two reasons -- one is because I cave dive, and need to remain current with my valve shutdowns and also with the strength to carry the darned things. The other is for deep dives or for what are essentially solo dives (dives mentoring new divers). They are GREAT to dive (although one does notice the increased effort to push them through the water) but a major PITA to haul around on land. Some charters are poorly set up for them, too.

If you ever want to give a set a try and see how you feel about carting them around and diving them, shoot me a PM. I've got spare sets.

 

[DA Aquamaster]

I also dive doubles nearly all the time. The only exception is dives where I have to fly on an airline to get there.

My reasons are identical to TS&M - familiarity with my cave diving configuration, deeper offshore dives, and dives with newbies who are very nice and very enthusiastic but not your first/best/preferred choice in the event of a failure.

I also prefer how doubles feel and trim in the water compared to most singles and in the real world that by itself is reason enough to dive them.

One thing I have found on the normal DE/VA/NC 80-130 ft recreational wreck dives is that with doubles I can carry one set of doubles on the boat and do both dives. You use no more than half the gas on the first dive and use the remainder on the second. On most recreational boats, you can't really do more than maybe 5 or 10 minutes of deco without holding things up, even if you are the first person off the boat, so you have less bottom time on the second dive and you still retain a healthy reserve. In contrast to two singles where the reserve gas from dive 1 stays on the boat during dive 2, the reserve gas from the first dive comes along on the second dive so it is very efficient. And you don't have to switch tanks between dives.

In the 70's and 80's it was common for divers to use doubles with a single outlet manifold. The idea swas not to increase redundancy but rather to either have more gas or be able to take along only one set for two dives as described above. Doubles were not considered magical or all that technical and the only caution was that doubles provided you with an awful lot of gas to get yourself in trouble with. It was not, and still is not, rocket science, but it does require some adjustment and practice as most recreational equipment today is not designed for use with doubles.

If you think you might end up going the techncial route eventually, it makes sense to start suing doubles at the recreational/non-deco level as they do swim differently and impact your entire configuration in terms of buoyancy, weigthing, wing, regulators, fins, etc. and any technical classes will go a lot smoother if you have 50-100 dives in doubles with perfect buoyancy and trim before you show up for class. For example, your first tech class is not the place to try doubles and a dry suit for the first time and/or discover your split fins don't have the muscle to efficiently push you through the water at a decent pace with all the extra drag and equipment.