Here it is explained better why an Y-valve is significantly safer than an H-valve:
H-Valve vs. Y-Valve
Why extra air when solo?
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H-Valve vs. Y-Valve
Divectionist
Contributor
These valves don't do it for me because as a DIN user (without any real world O ring redundancy benefit from having two) and a top notch well maintained first stage, my main 'fear' behind my head is that the tank valve on some shoddy rental tank gets clogged. Then two regs on one tank that gets clogged below that system don't help either.
Y-valves have two separate small pipes getting air from the inside of the cylinder, it is very rare they are both clogged simultaneously.... This is another reason for the superiority of Y-valves to H-valves.
Regarding DIN regulators not breaking the O-ring, watch this video here below and evaluate yourself. It is true that they loose less air than a joke, but still the O-ring can fail...
And in my experience I had at least three cases of regulators stopping working as debris was obstructing the air flow (once inside the bottle, and twice at the metal filter in the regulator). When you rent bottles, you do not know what is inside them...
I really do not see the point of using an octopus, we are here searching for safe practices, and definitely using two separate first stages with a proper Y-valve is much safer than an octopus...
If I were to swim down 20ish feet and then whilst am swimming around the O-ring fails on my unreliable yoke equipped double hose regulator, I think I will just swim back up the 20ish feet. That is just me though, I know y'all got to make it all complicated. N
Divectionist
Contributor
When I googled the Y valve it looked like a few have double pipes and most only a single, but that's just a matter of picking the right item, you are right if there are indeed two.
Yes the O ring can fail on DIN, but the gas loss shown in the video is at least not 'surprise OOA' territory.
As soon as there is more than one reg and sufficient backup gas source, I would ditch the octo from the primary reg as it has very little practical use.
There is no 'right' config for backup air, as it all depends on the circumstances. As long as it is truly redundant and has enough juice to get you back safely, it's good in my book. You just got to love having a major issue to your main air supply being an inconvenience and not a major stress situation.
Three cases of blocked reg/valve is quite a bit - you've got many dives but still... How did you manage these situations?
I recall the three cases.
1) the suction pipe into the bottle was clogged. This was giving intermittent air flow, depending on the attitude. When staying head-down there was no air at all, when head up there was some...
In that case I had a 15-liters steel bottle, with rust inside, with an H-valve, and i learned the hard way the importance of two suction pipes in the bottle for true redundance. However I managed to make a regular ascent, as when going up there was enough air. At that time (it was during the eighties) I was mostly diving with my Technisub Aralu twin (9.5+9.5 liters), so I also learned that using rented bottles form not reputable sources is not a great idea...
2) One reg out of service due debris in the air filter. No problem at all, I simply used the secondary regulator (as said, here almost every bottle has two valves, and I always use two independent regs, when possible)
3) The third case occurred when I and my son were doing some scientific activity at the Trieste-Miramare marine park. We had to install a three-dimensional hydrophone probe close to the jetty, at 15m from it and at a depth of 4, or perhaps 5, meters. I was snorkeling, or, better, freediving, my son borrowed a bottle form the park administration: it was a 12 litres cylinder, with a good Y-valve, but they gave him just a single Din-to-yoke plug, se we could not use the second regulator and there was no time for reconfigure them as an octopus. In the end, he had just a single second stage. After a few minutes he did signal me that he was getting very little air, even pressing the button just a small column of tiny bubbles was coming out.
Working mostly in apnea (as me), and with the help of Linda, the local divemaster, we still managed to install the hydrophone probe and to perform the experiments, which later allowed to publish the paper linked below. Due to the minimal depth, a scuba systems was really optional in that case, and my son managed to complete the job using the very little air which was indeed coming out.
Here the paper: http://www.angelofarina.it/Public/Papers/265-Springer-2012.pdf
And here a presentation which provides much more detail on those experiments...
http://www.angelofarina.it/Public/Presentations/UAM2011_Underwater_Ambisonics.pdf
On slide 27 you see my son, on the right, who is attempting to breath from the regulator, with almost no success... Linda was on the left. I was taking the photo, of course in freediving.
When I look at data, I tend to discard outliers. The clogged tanks or clogged regulators or whatever they were are the result of poor equipment maintenance and use of equipment from unknown sources. The dip tubes must have not been on the valves.
Equipment malfunction due to tank valves not being equipped with a dip tube to prevent clogging or tanks so choked with rust that the sintered filter becomes clogged do not carry any weight in the argument because they rate into the area of bizarre. The lesson there is not to have "extra air" but to maintain the diving equipment. In such cases as these presented, would quadruple redundancy be enough? How much extra air is needed when diving with poorly maintained equipment? In any case, just go to the surface, clogged tanks do not prevent going to the surface in the OPs original post.
And while at it, to reiterate, diving accidents that result from (or after but not resulting from) buddy teams unintentionally becoming separated or intentionally separating when not originally intending to do so are not solo diving accidents, they are buddy/team diving accidents resulting from buddy diving gone wrong. If a buddy teams becomes seperated, what is the buddy team supposed to do? Not continue the dive, but go to the surface. Solo diving is not accidental.
N
Equipment malfunction due to tank valves not being equipped with a dip tube to prevent clogging or tanks so choked with rust that the sintered filter becomes clogged do not carry any weight in the argument because they rate into the area of bizarre. The lesson there is not to have "extra air" but to maintain the diving equipment. In such cases as these presented, would quadruple redundancy be enough? How much extra air is needed when diving with poorly maintained equipment? In any case, just go to the surface, clogged tanks do not prevent going to the surface in the OPs original post.
And while at it, to reiterate, diving accidents that result from (or after but not resulting from) buddy teams unintentionally becoming separated or intentionally separating when not originally intending to do so are not solo diving accidents, they are buddy/team diving accidents resulting from buddy diving gone wrong. If a buddy teams becomes seperated, what is the buddy team supposed to do? Not continue the dive, but go to the surface. Solo diving is not accidental.
N
Divectionist
Contributor
Thank you for the recap and good luck for your further research.
Yup, I really tried hard to stay away from buying tanks because I'd have to go to the shop for fills anyway and owning tanks in Australia is 5 times the hassle than elsewhere, but I could not continue to put up with unreliable shops, begging for rentals, and getting banged up crap to dive with.
At least now I can dive exactly what I like - steel 85.
Yup, I really tried hard to stay away from buying tanks because I'd have to go to the shop for fills anyway and owning tanks in Australia is 5 times the hassle than elsewhere, but I could not continue to put up with unreliable shops, begging for rentals, and getting banged up crap to dive with.
At least now I can dive exactly what I like - steel 85.
This time I am really leaving this thread, it has run a useful and now not so useful course.
Mate, is it three failures you have had with clogged valves and regulators, maybe I need to go back and read all of that? Seriously, be careful please. Please.
I am buying my wife an auxiliary bottle. She does not know it yet. But she will soon be incorporating a 6 cf bottle and regulator, slung. She is a tiny little thing, 6 cf is plenty to hold her over until I, Nemrod, arrive on the scene. The 6 cf is for me, because, now at 66 yo, I need that time allowance to get to her, should there be a problem develop whilst I am about photoing fish tales, or my fav, anemones of late. I do not trust anything or anyone but me and when I cannot trust me, I will stop diving.
N
Mate, is it three failures you have had with clogged valves and regulators, maybe I need to go back and read all of that? Seriously, be careful please. Please.
I am buying my wife an auxiliary bottle. She does not know it yet. But she will soon be incorporating a 6 cf bottle and regulator, slung. She is a tiny little thing, 6 cf is plenty to hold her over until I, Nemrod, arrive on the scene. The 6 cf is for me, because, now at 66 yo, I need that time allowance to get to her, should there be a problem develop whilst I am about photoing fish tales, or my fav, anemones of late. I do not trust anything or anyone but me and when I cannot trust me, I will stop diving.
N
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