I have that addition. Will have to look it up
Quiz - Equipment - J-Valve
- Thread starter Pedro Burrito
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Yes, "interpret" is a key word.
The 1968 literature posted seems to indicate if you have 300 PSI in reserve that ain't so good if you're really deep, so depth matters.
Says there should be enough to get you to the surface-- doesn't say how close to completely emptying your tank that may be.
The 1963 literature is selling J valves and recommends having one on any dive greater than 30'.
Seems that more divers than not would plan to use it as part of the dive plan. But I don't know what sort of majority that would be. I don't think I would. Think I'd use it if my plan went askew.
So, all of this does relate back to the question and whether the 300 PSI is considered extra or not.
I still don't think the "extra" discussion is very important. We know how the valve works & what happens.
The 1968 literature posted seems to indicate if you have 300 PSI in reserve that ain't so good if you're really deep, so depth matters.
Says there should be enough to get you to the surface-- doesn't say how close to completely emptying your tank that may be.
The 1963 literature is selling J valves and recommends having one on any dive greater than 30'.
Seems that more divers than not would plan to use it as part of the dive plan. But I don't know what sort of majority that would be. I don't think I would. Think I'd use it if my plan went askew.
So, all of this does relate back to the question and whether the 300 PSI is considered extra or not.
I still don't think the "extra" discussion is very important. We know how the valve works & what happens.
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Sorry my bad. I just saw "Highly recommended... $30". Missed the "despite the price". Doesn't change what I said in my post.
I know you've given me statistics on PSI needed to surface from various depths and no doubt they are 100% true. I would ask though, would you plan a dive to say, 100' (or even deeper) and plan to begin an ascent with only 300 PSI?
Saying that book is trying to sell you a J-valve is inaccurate and disparaging.
Of course I would prefer not to ascend from 100 ft with 300 psi. I also prefer to go much slower than 60 ft/min and to do safety stops.
What is your point? That quote and those valves and that type of diving are from over half a century ago, and are not consistent with today's diving.
captain
Contributor
I have made the standard accent back in the day, 60 fpm, from 80’ on 200 psi with air to spare.
AfterDark
Contributor
That was why I bought a SP tank and J valve with an adjustable reserve 300 or 800psi and a built in gage. Ice diving deep diving I'd use the 800 psi. Was it adequate? Yes and No I always surfaced with air left, but by todays standards no. Today after a SS a diver is expected to surface with 500psi.
I also have a pedestal type J valve that's over 50 years old; to the best of my knowledge the only things ever done to it was O ring changes. The SP fancy J valve is in a box unserviceable. I'm still using the pedestal valve.
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I made a mistake, didn't notice the author too, apologized. Rub it in, why don't ya.
My point about ascending with 300 PSI from 100' was worded unclearly on MY part this time. I pointed out myself way back that of course diving is different today--safety stops, maybe being back on board with 500 PSI (as AfterDark just mentioned as well).
I MEANT to ask-- If you were using a J Valve tank 50 years ago would you plan on beginning your ascent from 100' by releasing the J valve pin and using that 300 PSI reserve-- as part of your dive plan back then?
Just trying to get another opinion from a veteran diver, in my quest to determine the all important question-- Is that 300 "extra" air? Is letter "C" correct too?
No, it is not extra air. It is part of your basic air supply that you set aside as a reserve for your ascent. All the J-valve does is alert you that you now need your reserve, and (when pulled down) gives you access to that reserve.
No, I would not have gone to 100 ft with a J-valve unless it had been st to a higher break pressure.
FYI, here is how much gas you need to get to the surface, for an RMV of 0.7 cuft/min, from various depths, for yesterday (60 ft/min and no safety stop) vs today (30 ft/min with a 3 min safety stop). The 450 psi needed from 130 ft, and getting back with 500 pis still in the tank, is where the "leave the bottom at 1000 psi" comes from. All this presumes an AL 80, and no panic.
I had a spiro 72 with reserve valve when I started diving but never thought of it as extra air or reserve ( which it wasn’t until the dive was over) when I pulled the bar I would move into shallow water and use it. I never dived without a snorkel for that reason.
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