What's the deal with H-Valves?

[DmitriC]

I have been doing a lot of reading on this forum, and others, and have found a whole lot of negative opinions on the use of H-valves. I'm wondering where all of this is coming from. I see the H-valve as being the best of both worlds: a single tank for simplicity and cost, but dual 1st stage regulators for redundancy. Maybe it's due to my lack of diving experience, but I don't see why everyone dislikes them, Any insight would be greatly appreciated.

-Dmitri C.

 

[cool_hardware52]

IMO, H valves are sort of ugly training wheels. The single tank recreational diver doesn't need them, they need a qualified, like minded team mate who will be carrying their back gas / brain / etc.

Dives that require genuine redundant gas sources need real doubles, or multiple independent cylinders.

Who does that leave for H valves? Divers in that odd gray area between recreational and tech. It's a purgatory that few linger in.

Hence "H" valves usually end up alone and unloved in the bottom of the "Gee I wish I didn't buy those" box.

If one does actually need two orifices on a single cylinder "Y" valves are a much cleaner solution too.

Tobin

 

[Lorenzoid]

The only scenario in which an H-valve has made sense to me that I have read about is diving in environments in which the water is very cold, yet the diving is most commonly of the plain ol' recreational variety. In other words, people are not doing especially long or deep dives, but they want redundancy in case the first stage freezes up. In that case, the diver handles the event as he would any sort of "emergency" event in a recreational diving context: abort the dive and ascend. One might ask why not just utilize one's buddy to donate air in the event of a freeze-up, rather than switch to a redundant first stage. If I recall correctly, the answer I have read is that when two divers are sharing a first stage, the likelihood of a freeze-up is increased due to the increased flow. So in this limited scenario, an H-valve (or Y-valve) might have some utility.

Other than that, what Tobin said.

 

[Tribal]

With Nelos (the belgium Cmas fedaration) they are mandatory for the dive leader.
Mostly because of the change of a Frozen first stage

 

[2airishuman]

I have been doing a lot of reading on this forum, and others, and have found a whole lot of negative opinions on the use of H-valves. I'm wondering where all of this is coming from. I see the H-valve as being the best of both worlds: a single tank for simplicity and cost, but dual 1st stage regulators for redundancy. Maybe it's due to my lack of diving experience, but I don't see why everyone dislikes them, Any insight would be greatly appreciated.

-Dmitri C.

I had some on my cylinders for a while and removed them after I figured out that I hated them. Let me count the ways.

1. At least on my 7.25" diameter cylinders, the H valve projects beyond the cylinder radius and bumps into things when the cylinder is being handled or transported, with the potential for damage both to the H valve and whatever it hits.
   
   
2. Reg placement and hose routing are a problem, because the regs are in different spots than they would be for a twinset. So you can't necessarily use the same hose lengths and routing for a twinset as you can for an H valve. You also can't necessarily use the same hose lengths and routing for a left H valve as a right H valve, which you might want to do if you could, because you might want to be able to twin up a pair of cylinders later that you're using with H valves now. Generally speaking the reg placement is problematic because the side reg is too low and tends to interfere with the wing, depending on how high or low you place your cylinders. Hose wise the main problem is the SPG hose, which is going to have to be several inches longer for an H valve than a twinset, although the BC hose may be off too.
   
   
3. You may have trouble reaching both valves, depending on your shoulder mobility. I can, but not everyone can.
   
   
4. An H valve is not a good alternative to a plain cylinder valve for ordinary open-water diving where redundancy is not required. The extra reg is a hassle in environments where it isn't needed, and plugging one outlet is a poor choice because the H valve still gets in the way and sooner or later someone will crack the valve so that you have to remove the plug with a wrench and trepidation. Using two regs on a low-risk open water dive is a poor choice because it adds needless drag, complexity, and time, and takes away from the relaxing simplicity of an easy dive. So ultimately you need to dedicate cylinders to activities that require redundancy, and as a result, the cost savings aren't that great.
   
   
5. Dives that require redundancy require a larger reserve of air, which means you need to bering a good deal of air. Even a larger single with an H valve doesn't have the capacity needed in most cases. Keep in mind that double HP100s are considered too small for general technical diving.

You can get used twinsets for around $450 and that's the way to go if you want to explore redundant regs.

 

[Scared Silly]

When I started diving twin sets I had a couple of cylinders with H-valves. That made it easy to switch back and forth between singles and doubles with the same regs. Then I bought another reg set for travel and singles. Then I sold the H-valves.

As Lorenzoid noted, H-valves probably make the most sense for for cold water recreational diving.

 

[gcarter]

The only scenario in which an H-valve has made sense to me that I have read about is diving in environments in which the water is very cold, yet the diving is most commonly of the plain ol' recreational variety. In other words, people are not doing especially long or deep dives, but they want redundancy in case the first stage freezes up. In that case, the diver handles the event as he would any sort of "emergency" event in a recreational diving context: abort the dive and ascend. One might ask why not just utilize one's buddy to donate air in the event of a freeze-up, rather than switch to a redundant first stage. If I recall correctly, the answer I have read is that when two divers are sharing a first stage, the likelihood of a freeze-up is increased due to the increased flow. So in this limited scenario, an H-valve (or Y-valve) might have some utility.

Other than that, what Tobin said.

On a recent cold deep dive, 5 of 10 people in the water had free flows. 2 of those 5 were caused by the extra load on the 1st stage from buddy breathing. The problem resolved above the thermocline. My preferred solution on these dives is a 40CF pony.

 

[Caveeagle]

On a recent cold deep dive, 5 of 10 people in the water had free flows. 2 of those 5 were caused by the extra load on the 1st stage from buddy breathing. The problem resolved above the thermocline. My preferred solution on these dives is a 40CF pony.

Wow, those are some bad % of failures. I'll try not to threadjack, ... but damn!

At one point, intro, or basic cave diver training was limited to single tank. I rented Y valve tanks for that purpose, but just bought manifolded doubles to avoid that awkward step.

I know some guys who dive in some small "no mount" places. An H or Y valve would be the only way to maintain full redundancy in that situation .

 

[gcarter]

Wow, those are some bad % of failures. I'll try not to threadjack, ... but damn!

Complacency. There was a serious post mortem following that dive. Should not have happened given the experience level of all involved. On the bright side, they all reacted quickly and calmly to resolve the individual situations, they all knew what to do.

 

[chrisch]

When I started diving twin sets I had a couple of cylinders with H-valves. That made it easy to switch back and forth between singles and doubles with the same regs. Then I bought another reg set for travel and singles. Then I sold the H-valves.

As Lorenzoid noted, H-valves probably make the most sense for for cold water recreational diving.

I have H valves for the same reason. I don't see any downside to them but at the same time I wouldn't get excited about not having them. They are good because they don't overstress the 1st stage as discussed but again this can be over exaggerated as a problem.

Perhaps people that make a big deal of it have nothing better to get upset about?