The evil J valve ?

[scubamitch]

One of the dive charters used by our club had a DM on board from a local dive shop who warned me about my tank and its valve. 500psi and you pull the lever down for the reserve, I always had the lever in the down postion and tossed the rod away years ago. Is this valve anything I should be concerned about? It is on a AL.tank 1980 vintage.

 

[herman]

Be more concerned about know it all DMs and instuctors that don't have a clue what they are talking about.
I dive a lot of vintage gear so I use a J valve as it was intended to be used. The valves are no different than a normal valve if you just put the lever down. If you mistakenly put it up, all it will do is make your SPG needle bounce and if you ignore the bouncing needle down to 500 psi or so, your reg will get very hard to breath from, not impossible, just difficult which is the valve doing it's job letting you know you need to go to the surface. Move the leve down and you are back to normal. If you have ignored the SPG bouncing the entire dive you need a good rude awaking. As for the tank itself, it's likely made of 6351 alloy (think that is the correct number) which needs an eddie current inspection in addition to the normal vis. Many shops simply refuse to test or fill the old tanks due to either a total misunderstanding of the testing needs of the tank or just want to sell you a tank using the it's too old or unsafe as the excuse.

 

[spectrum]

The reserve was used in the days prior to pressure gauges. When breathing got difficult you pulled the rod and that let you draw on the last 500 PSI or so to get to the surface. There was always a risk of inadverdent premature pulling of the rod meaning when breathing got difficult you were soon OOA.

In a modern application just rotate the actuator down so 100% of your air is accessible and dive normally. If you have a dive where pressure seems to drop prematurely you can check that it didn't somehow get roatated up but that's about the worst thing that can happen.

I would not feel compelled to change it but for the sake of standardization you might keep an eye out for a sweetheart deal on a modern valve and swap it at the next VIP. Also some of the old valves have funky little knobs that are hard to operate but yours is OK.

Pete

 

[scubamitch]

Thanks for sending the info. You have re-newed my confidence in using this valve type.
Mitch.

 

[Nemrod]

I also have been using them for decades and there is nothing dangerous about them as long as you understand their use. However, valves are very inexpensive and I am pretty sure your cylinder is the bad 6056 alloy that is alleged to have cracked once or twice (being snarky). While I love vintage gear, real vintage gear, you should invest in a new manufacture 6061 alloy aluminum 80 or steel tank of your preference with a modern K valve.

So to summarize, your valve, meh, your tank, yes, it is indeed an evil thing. Many scuba stores, especially in Florida, statewide, will not fill them. Get a new tank.

N

 

[scubamitch]

Local shop has them on new for $100.00 I'm going to pick one up.

 

[Sevenrider860]

XS Scuba sells new J-valves.

http://www.xsscuba.com/valve_xsvalve_models.html

 

[DCBC]

I actually prefer a J-Valve in some circumstances. Although I had the unfortunate event of running OOA in the early days (before SPG's were always utilized) because the J-Valve was down when I needed it. I've also run OOA because of a defective SPG. If that happened again, I wouldn't be opposed to having a J-Valve available to me. Although there has been progress in equipment technology, that doesn't mean that well-maintained vintage equipment is dangerous (it certainly isn't).

Beware of people (including Divemasters and Instructors) who throw stones at things that they don't understand. There are divers on this Board who have more underwater hours using a J-Valve than these Divers may ever accumulate. It's a good piece of equipment if maintained and operated within its designed operational envelope.

Look at it as an insurance policy. Although not all insurance policies pay-off when they are needed, they're often are a good thing to have.

 

[drbill]

Back in the days before I had an SPG, I always dove tanks with J-valves. Sometimes the valve levers got pulled due to getting caught in the kelp and when I went to pull them they were already down. I still have one tank with a J-valve. However since most of us dive with SPGs these days, I see no problem with a J-valve on a tank.

 

[j yaeger]

the only prob you run into running a j valve without the rod
is forgetting to flick it down prior to dive...
...then thinking that you still have 500 lbs,maybe stay a bit longer...
then noticing that it's sucking hard...and you don't have the rod to pull...
then trying to be "gumby" and bend enough to reach the freakin' valve....
just saying!
remember to flick valve down first...DOH!!!!
have fun
yaeg