2 valves per tank, why?!

[broadreach]

So, after living in Europe (western Switzerland) for about a year, I finally decided to take the plunge and try the local lake diving scene. One thing that caught my attention immediately upon entering the local dive shop, is that 99% of the tanks had 2 (DIN) valves attached to them. Shop owner said that this was required by law in neighboring France (mandatory to dive with 2 first stages).
Sounds like overkill to me, but could there be something in the local environment that creates a need for this? maybe cold water?
any thoughts?

 

[divad]

could there be something in the local environment that creates a need for this?

Yes. France.

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[Scared Silly]

It is not a law in France (I lived and dove there), it is all about redundancy on particular dives.

 

[drbill]

Two valves on a single tank? Is this a Y- or H-valve? Not sure I understand. Unless the two valves have redundant air passages into the tank, and do not share a single pathway, the redundancy is not 100%. If they share a common pathweay and the single dip tube gets clogged, good luck. It happens. Believe me, I know from experience.

 

[TSandM]

If the local diving is in very cold water, freeflows due to regulator icing are a real issue. By attaching two first stages to the tank, with the ability to turn the valve off on either one, you have set yourself up for redundancy for a common and high-risk malfunction. (This is assuming the tanks were set up with H or Y valves, where you have the ability to close either side.) Yes, you are still in trouble if a dip tube clogs, but that is a far less frequent problem than cold water freeflows.

 

[stairman]

It is overkill to most, but being able to isolate a bad reg and return to the surface slowly is good for peace of mind .

 

[Lemna]

Most Swiss lakes are very cold below the thermocline.

This type of setup is very common in parts of Europe. It is required by the local CMAS affiliate here in Belgium for dive leaders, and advocated by almost all the local PADI instructors (and the one GUE instructor) I know. The rationale is that a frozen regulator is a much more common problem than a clogged dip tube or a blown tank neck O-ring.

 

[broadreach]

Here are a couple of photos just to show the configuration. Having done my first dive in the local lake :cold: the coldest for me so far (7C@30m or 45F@100F) I guess the issue is indeed free flowing regs and the ability to shut one down and bail out in a calmer fashion.

 

[Agility]

The use of two first stages is encouraged for diving in lakes in the alps and is mandatory in some destinations e.g. Kreidesee Hemmoor in Germany

 

[eelnoraa]

hmm, 45F at 100F doesn't sounds cold enough for H value. Or least it is not common in my area where water is 50F at surface all year around. I have seen 46F at 60ft