Just curious. Why did the industry stop making the J valve? I learned diving with this valve and dove many, many times with it and never had any problems or issues. Does anyone still dive with this type valve? Thanks!
J Valve
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Scuba Lawyer
Contributor
The industry did not stop making J-Valves. They are still made today. 
XS Scuba PVD Reserve J Valve - Dive Tank Valves - Scubatoys.com
XS Scuba PVD Reserve J Valve - Dive Tank Valves - Scubatoys.com
With the advent of Submersible Pressure Gauges why would it still be a good idea to dive with a J valve? They were a good idea before the ability to monitor gas pressure but not that we have that ability, and it is an industry standard, wouldn't this be considered an equipment solution to a training problem (gas management)?
GJC
Contributor
J Valves also had problems of their own.
During a dive, it could be bumped or pulled by something inadvertently. Then, when it became difficult to breath and you went to pull the valve, the valve was already open and there was no reserve.
Sometimes, if not checked before the dive, the valve could be in the open position with the same result as above.
During tank filling, if the filler did not have the valve in the open position, the tank would not be filled but the fill pressure gauge would show the max fill pressure. Then, when taken on a dive, the tank would only have what was in it before the fill was attempted.
During a dive, it could be bumped or pulled by something inadvertently. Then, when it became difficult to breath and you went to pull the valve, the valve was already open and there was no reserve.
Sometimes, if not checked before the dive, the valve could be in the open position with the same result as above.
During tank filling, if the filler did not have the valve in the open position, the tank would not be filled but the fill pressure gauge would show the max fill pressure. Then, when taken on a dive, the tank would only have what was in it before the fill was attempted.
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Wow, $484 with a pull rod vs. $60 for a K valve.The industry did not stop making J-Valves. They are still made today.
XS Scuba PVD Reserve J Valve - Dive Tank Valves - Scubatoys.com
CuriousRambler
Contributor
I've never used a J valve, but one thing mentioned in another thread recently is zero vis diving. I don't know what other solutions might exist, but a J valve might be just the ticket for a public safety dive in a no-vis reservoir or the like.
Scuba Lawyer
Contributor
I've posted these pics before but seemed appropriate here. These are two of my working J-valves I have on a couple of 71.2 steel tanks. I like the Dacor valve as it has a port for a SPG that can be accessed when the tank is full but the valve is off.
Apparently you are immune to the "mil-spec black PVD" finish. It is shiny. Some people don;t have the anti-bodies to fight that. Thankfully, I must have had it as a kid because I am also trying to figure that out. Doesn't even come with the $34 pull rod. Maybe it is made out of unobtainium.
perhaps but I would think using surface supplied air would be a much safer bet if doing true zero visibility diving.
Must_dash
Contributor
For the pressure, I'm assuming you mean the J valve is off?
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