Choosing Components for Doubles

I get asked many times about what kind of doubles people should get when they want to move into technical diving. Should they get 130s, 100s, 120s, or aluminum 80s? There is no one right answer for selecting which size tanks. However, special consideration must be made in regards to selecting the manifold, valves, and bands to build that set of doubles.

Selecting Tanks

Selecting the right tank size is tricky. The deeper we go, the more compressed the gas we breathe. Therefore, we consume much more gas on deep dives than on shallower dives. I only own four sets of double tanks. Two sets are 130s and two sets are aluminum (AL) 80s. My personal rule of thumb is that if I’m going deeper than 100 feet, I want as much gas as I can take with me. So I use my 130s. If I’m doing shallower dives, less than 100 feet, then I’m using my AL80s. The AL80s give me plenty of gas for long recreational dives. With these to sized tanks, I can cover my technical dives and recreational level dives. So I don’t have to deal with 100s or 120s for the deep, but not too deep technical dives. The 130s serve me well.

I do get a bit of ribbing from folks who think AL80s are “girlie” tanks. Don’t make the mistake and think that double AL80s are not a useful configuration. Sure, you don’t get the extra weighting that comes with steel tanks. But they are easy to handle when on land. Especially if you have a long walk; on a hot day; in a dry suit, to get into the water. Double AL80s give approximately 175 cu ft. of gas. This is plenty for a day’s worth of diving at my favorite quarry without needing to get more air fills. AL 80s are great tanks for beginners because they are cheap and easy on the back.

If you do decide to get AL80s for your doubles, you don’t need brand new tanks (i.e. original hydro dates less than 2 months old or whatever). A set of new AL80 doubles will cost between $500-$700 (with manifold and bands). Aluminum tanks fail visual inspection far less than steel tanks. So the AL80 will last you quite a while. Pick up a couple used AL80s to double up and use that extra money you saved from buying new tanks and put it towards a quality manifold and bands.

Choosing the Important Stuff

Regardless of the size of tanks you choose to double up, the most important components you should be focusing on is selecting quality manifold and tank bands. The considerations you should think about when selecting a manifold are: how easily the valves open and close and how many turns it takes to open/close the valves.

I like two manufacturers of manifolds, Halcyon and Dive Rite (only the VA3000 series). Both are very similar in design, the knobs turn easily and can be closed/opened in five turns or less. I once had a Thermo manifold. The chrome plating started chipping off the DIN threads and would lodge in the regulator’s DIN o-ring. Thus causing small leaks. So I’m a little put off by the Thermo and XS Scuba manifolds. I don’t know much about others such as Sea Elite and HOG/Edge. But my preference is the Halcyon and Dive Rite mentioned earlier and I would pay a few extra dollars for them.

Just as important in selecting a quality manifold is selecting strong tank bands. The biggest feature to consider when purchasing bands is the weld. Bands are made in two pieces and then welded together. If that weld is not strong, the bands can break apart. Certainly not something you want to happen with 3000+ psi of pressure in them. Below are pictures of a weak weld and a strong weld.

It is also important to mention that the bands must be matched with the manifold. Meaning, that if the space between the bands is too big or to small, the isolator part of the manifold will not fit properly into the valves. So make sure, when you purchase your bands, that they are compatible with your isolator. Most will have a sticker on the inside of a band that says which manifold manufacturer will work with those bands.

Summary

If you are considering moving to doubles or start technical diving, then seriously consider using AL80s for your first set of doubles. Ask any avid technical diver, you will quickly start to accumulate many sets of doubles. The double AL80s are great for practice and shallow water work and will last you a long time. New or used AL80 tanks will work just fine. Most importantly, make sure you purchase a quality manifold and tank bands.

Dive Safe,
Duane
Precision Diving

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