What would you do with a J-valve?

[g2]

No fair reading the discussion until you've answered the poll!


A recent thread discussed why you might need to reach around to your tank valve during a dive. I was surprised that nobody mentioned J-valves. These things are still in use in some places; I know because I serviced a couple of them the other day.

It got me curious: what would most divers do when confronted with one? Assuming, of course, they know what a J-valve is and how it works! My answer would vary depending on the type of dive, phase of the moon, and how much skin is peeling off Michael Jackson's nose...

Pop Quiz for Extra Credit! Your air-integrated dive computer reads 3200PSI before the dive (goody) and everything looks great. Moments into the dive your computer goes nuts. Why?

 

[DiverBuoy]

And add it to my scuba under glass collection ...

 

[richhagelin]

Since most of the readers of this board are too young to remember (I learned to scuba dive with a double hose regulator, which most of you won't know about either, but , I digress). The J-valve was for the days before underwater pressure gauges. It allowed the diver to know when he was beginning to run out of air because it became rather difficult to breath. By activating the J-valve (which was a 1/4 rotation lever normally activated by a pull-down lever on the side of the tank), the diver then opened a wider channel for the remaining air in the tank and breathing was normal and you surfaced). Believe it or not, that is the way it was done in "the olden days"


Rich

 

[SwimJim]

Using the J in the down position renders it a K valve. Thats the way it should be used. In the olden days when an spg was a luxury the J did have a use. I remember diving a wreck in sixty feet of water.(Iwas diving solo) I felt the resistance in my trusty Dacor Olympic 100(my first reg) and knew I was on reserve. I reach back to pull down the rod that actuates the J valve. I could not find it of course. No problem, I performed a text book ESA.
I'd much rather have an SPG then rely on a J valve to get me out of trouble. Or keep me out of it in the first place.

Jim

 

[Bubble Boy]

If you are going to use a J-valve get a wire tie and tie it in the down position.

 

[devilfish]

So how did the two valves got thier names K & J?
Hagelin, shhhh.

 

[scuberd]

devilfish once bubbled...
So how did the two valves got thier names K & J?

those were the cataloging letters assigned to them by the company (I don't know which one) that origanally marketed them.

 

[Bob3]

http://www.geocities.com/athens/atlantis/2427/divecat/index.html
Compliments of my buddy Bill unningham.
May take a little while to load.

I still use a few tanks with J valves, keep 'em down all the time.

We'd remove the pull rods & just reach back to turn the reserve on, one less place to get fouled & make mischief.

 

[pescador775]

The short nick names for tank valves originated about 1955. Actually, I think I may be one of those who started the practice. In those days, there was only one dive equipment brand of significance, the Navy approved Aqualung, sold by US Divers. The company offered three valve designs. Their names for these valves were 'constant reserve' (cat no J), 'positive reserve' (R) and 'non reserve' (K). It was just easier to refer to the valves by their cat nos.

The J valve is no more 'primitive' than an SPG. It probably employs engineering knowledge and manufacturing skills similar to those of a pressure gauge. Oh, sometimes they are accidently bumped into the 'on' position but J valves are more rugged than gauges and they don't explode. I've seen the faces blow off of three gauges at varying times. Nowadays, they are fitted with a blowout plug, like a tank valve. Of course, we know about SPG's and their weak connections and O ring maintenance. By comparison, the J valve is lower drag and less hassle. However, over time, J valves, like any valve, are subject to maintenance. The internal reserve spring may become weak, or the seat wears a groove, or the stem O ring becomes stiff.

The J valve is a good choice for no decompression, straight up and down dives. The gauge is needed when complicating factors like decompression, overhead and current are part of the profile/plan. A diver who is subject to the 'thirds' rule cannot carry out a plan safely with only a J valve and no means to monitor pressure. One thing that makes a vintage dive fun is to unburden oneself of the hanging appendages; dangling single hose regs, multiple accessories and multiple hoses. Slinging on a compact set of tanks with a double hose hanging comfortably around one's neck and a J valve pull rod fixed snugly to the tank (and close at hand) is not a bad thing.

 

[SMan]

Leave it on. That is how it was taught in my OW class this past May. The LDS that I rent tanks still has some. With the current state of equipment, it really is just one more thing to think about. Plus I have seen others either forget to put it in the on position or turn it on and not the main one (if that is the correct terminology).