Diving with redundancy.

[Nemrod]

I was just curious what others thought about diving with an H-valve while diving recreationally? Seems like a good idea to me for redundancy and self-reliance, but I’m not sure of the downside if any.

Thanks in advance for your insight.

Kevin

Your buddy is your redundancy. The entire buddy system is based on that concept. If you are progressing towards being a solo diver then an H valve is a half step and not a good one, IMO a half step backwards. It creates complexity and more failure points while at the same time not offering true redundancy. Think it though. A slung auxiliary bottle would be a better choice. It provides true redundancy and is acceptable for solo or self reliancy per both SDI and PADI.

I will add, if this is in relation to a regular buddy (wife, friend, brother, whoever) then your buddy/team skills need to be addressed. If this is in regard an insta-buddy, you have my sympathy, then proceed with due consideration of exactly what it is you wish to accomplish, a H valve is not true redundancy.

N

 

[Angelo Farina]

Your buddy is your redundancy. The entire buddy system is based on that concept. If you are progressing towards being a solo diver then an H valve is a half step and not a good one, IMO a half step backwards. It creates complexity and more failure points while at the same time not offering true redundancy. Think it though. A slung auxiliary bottle would be a better choice. It provides true redundancy and is acceptable for solo or self reliancy per both SDI and PADI.

I will add, if this is in relation to a regular buddy (wife, friend, brother, whoever) then your buddy/team skills need to be addressed. If this is in regard an insta-buddy, you have my sympathy, then proceed with due consideration of exactly what it is you wish to accomplish, a H valve is not true redundancy.

N

Nemrod, I agree with you, but you are answering a question different from the one of the OP. He did not ask about using two regs on the same single cylinder, he just asked if getting a cylinder with an H valve is a good idea.
It is not the same question.
You assumed that the second post will be used for a second reg.
This happens very rarely in my experience.
Here in Italy most rental cylinders are 15 liters with double valve (H or Y). I would never rent a cylinder with just a single post, as this is less reliable.
Then I dive with a single first stage, with DIN attachment, which is perfectly fine for rec diving.
So my answer to the original post is: yes, a cylinder with an H valve is a valuable asset, as it allows you to go on if one of the valves has a problem, mounting your reg on the other post.
I am not the only one thinking this way. In fact, most cylinders here are with two valves, exactly as the users like them...

 

[Open Ocean Diver]

Your buddy is your redundancy. The entire buddy system is based on that concept. If you are progressing towards being a solo diver then an H valve is a half step and not a good one, IMO a half step backwards. It creates complexity and more failure points while at the same time not offering true redundancy. Think it though. A slung auxiliary bottle would be a better choice. It provides true redundancy and is acceptable for solo or self reliancy per both SDI and PADI.

I will add, if this is in relation to a regular buddy (wife, friend, brother, whoever) then your buddy/team skills need to be addressed. If this is in regard an insta-buddy, you have my sympathy, then proceed with due consideration of exactly what it is you wish to accomplish, a H valve is not true redundancy.

N

Well I guess I should’ve been more specific I was thinking the H-valve using it with two first stages, I was also told that it would probably be better with two dip tubes which would make the two valves independent on one tank. Of course this would require me to shut one of the valves off in case of failure which seems a little clumsy. Yes we could probably do more practice with the buddy system my wife is my buddy but I feel maybe we don’t have enough practice and I worry when at 100 feet and say an LP hose failure and she’s a bit of A distance away would I panic and bolt to the surface. I learned a valuable lesson last year I had an inflator hose fail in the open position luckily I was close to the surface, my BC auto inflated and the PV went off I wasn’t sure what was happening but it ended my diving since my valve stuck open. I learned from the dDM I should’ve disconnected my LP hose going to the inflator. I don’t remember learning that in my training. If I’d been at 100 feet I would of zoomed to the surface... valuable lesson. I posed the question to somebody that recently completed there rescue course, the question was what would she do if your BC auto inflated, she replied with stretching her arms and legs out to slow her ascent never mentioned disconnecting the BC LP hose to inflator. Training is one thing practising for all possible circumstances is another, experience seems to be the most valuable. Thats why I was thinking of a back up redundant system, seems to me from everyone’s input that the 19 cf pony bottle slung is the best choice.

 

[Open Ocean Diver]

It's been my experience that 99% of first stage failures happen on the initial pressurization or the first breath. That might be a conservative number. No, I haven't witnessed 100 first stage failures, but then I've never seen one fail at depth, either. I've seen some IP creeps, but breathing off of the reg will usually keep that under control. Most failures at depth seem to involve the HP hose or fittings.

There's really no need to overthink this. Your training taught you several methods to deal with OOA, all of which are still available to you. Since the most common failure is a ruptured hose, you really have a lot of time to deal with such a failure. You probably have enough time to make an ascent with such a failure if you act decisively. No, you won't be able to do a safety stop, just make your way on up.

Realistically, you can't prepare for each and every possible failure on a dive. Once you've covered that 99%, you'll have to rely on your training and creativity. That's really not such a big deal, is it?

I understand what you’re saying I will never really know until it actual happens and it may never, but you know in a car you have a hydraulic brake system with a brake on each wheel. Cars are still built with a mechanical emergency braking system in case of hydraulic failure. I’ve never had a brake failure in all the years I’ve been driving. But it’s still a standard and required in vehicles. I know first stages are extremely reliable with most with one moving part but hydraulic systems are also extremely simple but still have redundancy built-in. I remember growing up in California in the mountains there was runaway truck ramps where trucks if they lost their brakes could pull over and drive into, it would have gravel or something to slow the truck in a controlled way to stop the vehicle. And in tech diving you have stage bottles redundancy all the things to make things safer but in recreational diving we seem to just rely on the buddy system which I don’t know at 100 plus feet under extreme circumstances how well that would actually work. When I dove the Vandenberg the DM’s carried pony bottles and also had safety gas on the lines. Just thinking out loud.

 

[Angelo Farina]

A pony bottle, or, better, a set of proper sized twins (say, 8+8 liters) are the only true redundant systems. With two complete and independent regs, of course.
I love twins, it was the standard when I started diving (in the seventies) and I miss them...
No one was using an octopus at the time, it was considered highly unsafe to rely on just a single first stage.
O-rings were not the same quality as now, and with yoke mount their failure was quite common.
But finding twins for rental is becoming very rare nowadays.
So now I use a single first stage, BUT WITH DIN MOUNT.
I personally do not like the pony, as it makes me less streamlined. I love simplicity.
I only rent tanks with double DIN posts, indeed, as I find them more reliable. It allows me to switch the post in case of valve failure (which are common, when the cylinder is managed improperly and falls against hard objects).
In your case, as you did not even manage to detach the BCD hose when it was self-inflating, I think that manoeuvring the valves of a tank with two independent regs is not properly easy.
So in your case the pony tank is possibly the easier and safer way to get true redundancy and more safety.
As you will stay within NDL, you do not need a large additional tank. There are some really minimal, which are not a big problem to carry around...

 

[Jcp2]

There is some balance between physical redundancy and task complexity that is different for each person that will lead to increased real safety for one while decreasing it for another. For somebody who dives a few times a year on vacation, the exposure to risk is small, and the interval between practice is high. They probably don’t have their own gear, or if they do, it’s already asking a lot to have the one set of regulators safely serviced. Its a bit different for somebody who dives multiple times a month locally who is in the habit of keeping on top of everything on a regular basis.

 

[Fastmarc]

Thats why I was thinking of a back up redundant system, seems to me from everyone’s input that the 19 cf pony bottle slung is the best choice.

It wouldn't be a bad idea. You could both practice with it, clipping it off to each other in a simulated emergency. It would be a nice addition to your buddy system.
Unfortunately I do not have a regular buddy, so I carry a 19cf which I can confirm is no issue.

 

[jadairiii]

... but in recreational diving we seem to just rely on the buddy system which I don’t know at 100 plus feet under extreme circumstances how well that would actually work.. ..

This is the disconnect in "recreational" dive training and the buddy system. Other than GUE, very few, or no other, training agency actually teaches proper gas management for a "recreational" dive in 100 feet. At 100' a buddy team has very little time and usable gas to safely surface, as a team, on one tank (including safety stops). The "be on the boat with 500 psi" does not work in a 100' of water. This is not the fault of the "buddy team", but the fault of not teaching recreational divers the reality of OOA emergency in 100' and how much gas the 2 people actually need.

The failure to teach this information to new divers leads to the belief that (1) buddy system doesn't work; (2) they need additional gear (H-Valve/pony bottles, etc) to be safe. The fact is the buddy system doesn't work when the diver believes his/her usable gas in his/her 80 is the whole tank.

But, with that knowledge, the system works great with out the need of a lot of useless gear for a RECREATIONAL dive.

 

[MichaelMc]

I only rent tanks with double DIN posts, indeed, as I find them more reliable. It allows me to switch the post in case of valve failure (which are common, when the cylinder is managed improperly and falls against hard objects).

Angelo, this seems key. You are talking about one 1st on an H. Maybe for if one side did not work in setting up the gear, maybe for switching underwater. I think everyone else is talking about 2 1st for underwater failures.

 

[Angelo Farina]

Angelo, this seems key. You are talking about one 1st on an H. Maybe for if one side did not work in setting up the gear, maybe for switching underwater. I think everyone else is talking about 2 1st for underwater failures.

Using two first on an H was common when they were yoke-mounted, as the chance of an O-ring failure was high.
When I converted my regs to DIN (with the SP kit) I stopped using two first stages, for rec diving I find it superfluous.
So my recipe (for rec diving, single cylinder) is:
- Yoke: you need two first stages
- DIN: one first stage only