J Valve

[Eric Sedletzky]

J valves are great. Back when they were in regular use, people knew enough to know that you shouldn’t be at 100’ and need to pull the reserve. A trained thinking diver would have been paying attention to depth and time plus volume and starting pressure, and they would’ve been back in shallow water ending the dive when the lever needed to be pulled. When the SPG came out the saying was “Oh great, now any idiot can dive”, and it’s kind of true, people now have several trick ways of monitoring their air supply and they somehow still run out.
Unbalanced first and second stages are also a useful warning signal when air is getting low.

 

[captain]

I have a J regulator that I sometimes use.

J tank valves tend to leak down in a few weeks after a fill because the J valve is always pressurized. Parts availability is a problem and over the years the valve stems get corroded or scored. With a J regulator it doesn't matter.

There is no inherent reason a properly serviced and operating J valve will leak down, I have J valve tanks that keep pressure indefinitely. Besides air flows from the shutoff to the J valve and then to the regulator, if the tank valve is closed the J section is not pressured.

 

[2airishuman]

There is no inherent reason a properly serviced and operating J valve will leak down, I have J valve tanks that keep pressure indefinitely. Besides air flows from the shutoff to the J valve and then to the regulator, if the tank valve is closed the J section is not pressured.

The four that I have had are not like that. The J section is pressurized even when the service valve is closed.