two 1st stages on one tank

[mania]

Here in Poland most of the tanks have 2 valves (see the picture).

And most of us are using 2 separate 1st stages. The reason is simple - diving in the cold water - we're talking 37 - 45 F (3 - 5 Centigrades). When diving in cold usually diver breaths quicker so it's easy to freeze the first stage - and I saw it happening to every brand. So instead of having octopus - which in such situation is no help - we use back up first stage with back up second stage.
In case of freezing primary first stage we close the valve and switch to the back up first stage.
And we are talking recreational diving - not DIR or technical (you don't do these with one tank anyway).
So my question is mainly to all of you diving in cold water - do you do the same? Or maybe we Poles are crazy?
Mania

 

[Rick Murchison]

Well.... I don't very often dive in cold water, but I do use an "H" valve and two regs on single 121's.
Rick

 

[underwater daphne]

the swiss do it and i recently got a chance to try this system in lake zurich. it's very smart and if you dive in cold water it is a lot safer. since i practically only dive in warm water i don't have this.

 

[daveg1]

Here in Poland most of the tanks have 2 valves (see the picture).

And most of us are using 2 separate 1st stages. The reason is simple - diving in the cold water - we're talking 37 - 45 F (3 - 5 Centigrades). When diving in cold usually diver breaths quicker so it's easy to freeze the first stage - and I saw it happening to every brand. So instead of having octopus - which in such situation is no help - we use back up first stage with back up second stage.
In case of freezing primary first stage we close the valve and switch to the back up first stage.
And we are talking recreational diving - not DIR or technical (you don't do these with one tank anyway).
So my question is mainly to all of you diving in cold water - do you do the same? Or maybe we Poles are crazy?
Mania

While I have thought about using an H valve here in the winter, we have never had a reg reg freeze below water only on the surface. Our winter dives are usualy short and not deep and always with a buddy so we have not found a need for them. In the winter we will see temps as low as 30 deg water with air around 20 or so. If its colder than that we don't go. For ice diving we use ponies so its not much of an issue there eather.

 

[perpet1]

I use an H valve on occasion and it is fine. The only thing I would add is that there are additional skills one would want to know before using this system to realize the redundancy of this setup. I am talking about know how to shut off one of the regs if there is a free flow. I would also hope that your buddy is aware of your configuration should something happen and you need their assistance.

In short, although you state that this does not need to be a "tech" setup, you should be aware that additional training is recommended.

My Thaughts,
Pete

 

[Don Burke]

So my question is mainly to all of you diving in cold water - do you do the same? Or maybe we Poles are crazy?

If it gets really cold, I dive small doubles since I have them anyway.

Since first stage freezeup is of particular concern to you and you have no need for doubles, your way of addressing the problem looks fine to me.

 

[JDostal]

I use H-Valves all the time - I don't have a single tank without them. I like them for two reasons. I can easily switch from diving doubles to diving singles - I don't have to reconfigure anything to switch the tanks. It gives me additional regulator redundancy without having to lug doubles around if I don't feel like it. They are very nice.

 

[DA Aquamaster]

I normally dive independent doubles for this reason. Bottom temps here run 35-45 degrees through the summer and a frozen first stage is a possibility.

With an H or Y valve (or a non-isolator equipped set of manifolded doubles) shutting off a valve is required if you freeze up a first stage to prevent loss of all your air. With independent doubles, closing the valve to the frozen reg is highly desireable to conserve air but is not required as the worst case scenario if you do nothing will be losing all the air in one tank with ample air remaining in the other tank to use for a normal ascent, deco stops etc.

 

[Rubis]

French do it all the time too. There is no tank above 12L (98 Cft) without a double outlet.

Here in the States they primarely use double tanks for redundancy.

 

[MaxBottomtime]

I only have one single tank, but I use an H valve for the same reason as Omicron. I don't need to switch hoses around or have a dedicated reg for my single tank. 95% of my dives are on doubles, though.