What's this second valve for?

[kf7lze]

Saw a pair of tanks for sale that look like they each have two valves. What's this setup used for?

[Nwbrewer]

That's an H valve. Put a second 1st stage on the other post, and you have redundant 1st stages. Not quite as good as manifolded doubles for redundancy, but better than a single tank/single 1st stage. Don't see them much in the PNW.

[kf7lze]

Interesting. So, would I run two first stages each with one second stage? Or do people diving H valves end up with 3 or more second stages?

[CaptnJack]

Interesting. So, would I run two first stages each with one second stage? Or do people diving H valves end up with 3 or more second stages?

Two 1st stages with 1 second stage each would be "normal".
H and Y valves are not very common now that doubles have become so common amongst recreational divers.

[Dusty2]

It's Basically a pony setup without the extra bottle. Not much good in an OOA but if you have it setup right it allows you an alternate if you need to shut off a primary free flowing rig.

[CaptnJack]

It's Basically a pony setup without the extra bottle.

more like manifolded doubles but only 1 tank. doubles don't do you much good if your OOA either..

[kf7lze]

Thanks for the info. I was looking at buying those tanks, Worthington LP108s at Discount Divers Supply on Westlake ($300/ea) and was curious about the weirdness. I have a 17cf pony setup so don't see myself using redundant first stages on the H.

I guess I'll change the topic to, "Do you think Worthington LP108s are good tanks?" Looks like they're 97CF @ 2400 or the full 108 @ 2640, so not significantly larger than my Faber LP95 which I don't like very much, but with better buoyancy characteristics (-2 vs +2 empty).

[Dusty2]

Thanks for the info. I was looking at buying those tanks, Worthington LP108s at Discount Divers Supply on Westlake ($300/ea) and was curious about the weirdness. I have a 17cf pony setup so don't see myself using redundant first stages on the H.

I guess I'll change the topic to, "Do you think Worthington LP108s are good tanks?" Looks like they're 97CF @ 2400 or the full 108 @ 2640, so not significantly larger than my Faber LP95 which I don't like very much, but with better buoyancy characteristics (-2 vs +2 empty).

Not at $300! Unless there new that is.

[camerone]

I have a 17cf pony setup so don't see myself using redundant first stages on the H.

Very little point in doing so in the PNW waters. Doubles are a much better choice for any number of reasons.

The H or Y valves are used more commonly in two places: extreme cold water and overhead environments. In Antarctica, I've found they're fairly common, as first stage freezing is a real issue down there...although better technique and modern regulators have made this less of an issue. Many (most?) of the scientific programs don't use doubles, so they use the H or Y setup. I used them for diving down there for the freeze protection redundancy last time I was there (2009).

The other use is in cave diving, although it's less and less common. Cavern and intro can be taught with H or Y valves, although I don't know anyone anymore who does it that way... and my peering around Cave Country Dive Shop today (yes, I'm sitting in High Springs right now... ) pretty much confirms that.

[CaptnJack]

Thanks for the info. I was looking at buying those tanks, Worthington LP108s at Discount Divers Supply on Westlake ($300/ea) and was curious about the weirdness. I have a 17cf pony setup so don't see myself using redundant first stages on the H.

I guess I'll change the topic to, "Do you think Worthington LP108s are good tanks?" Looks like they're 97CF @ 2400 or the full 108 @ 2640, so not significantly larger than my Faber LP95 which I don't like very much, but with better buoyancy characteristics (-2 vs +2 empty).

Not at $300! Unless there new that is.

Never saw any discounts in there personally. But that's just me.

[kitsapdiver]

We used H valves for ice diving in Ohio because we were diving shallow and didn't need the gas of doubles! It's easier to roll over and face up to play with bubbles on the ice and what not. In ice diving free flows are very common! Not as necessary in salt water!

The thing to remember is that gas in the first stage is being broken down from tank pressure to an ip about 135-145 psi above ambient and when pressure drops its the opposite of the effect at the fill station instead of getting warm it gets cold!