J Valve justification

[ronski101]

Do any of you older divers out there remember why tanks used to have "J" valves on them? I believe it was so that when activated, you could have a few minutes more of air at the end of the dive. This was before tank pressure gauges were available. From a safety standpoint, I was wondering why they are no longer available?

 

[fdog]

Do any of you older divers out there remember why tanks used to have "J" valves on them? I believe it was so that when activated, you could have a few minutes more of air at the end of the dive. This was before tank pressure gauges were available.

This is correct.

From a safety standpoint, I was wondering why they are no longer available?

Because pressure gauges are available, and, you'd roll off the J once in a while (defeating their purpose). Also mechanical reliability issues.

They got the nickname from the USD catalog number - the non-reserve tank valve started with the letter "K", and the reserve valve started with "J".


All the best, James

 

[Darnold9999]

J valve was your reserve. When it became hard to breath you reached back and pulled the wire and you had enough air to end the dive. My recollection is that it was 300 PSI but it could have been more. I had a SPG so found it pretty much useless as, if you were monitoring your air, you already knew it was past time to surface anyway. If you relied on it and it had already been pulled, by kelp or something like it you were SOL and it was time to review your CESA procedures.

I gather from some earlier post that they are still in use when an SPG does not function - in 0 vis diving for example.

 

[Thalassamania]

They did not work dependably. The last thing one wants to have do at the end of a dive, when cold and tired, is to have one's air cut off and have to reach back hoping that you've not banged the lever against something, accidentally activated it, and are now really OOA.

Another problem was that a comfortable diver with a low SAC rate could often breathe right through the reserve without activating the lever, the seats leaked that much. Lt. Mike Fitzgerald of the U.S. Navy Safety Center made a point of inspecting the J-valves in the dive lockers or all the facilities he checked. He found that better than half the time the valves did not function properly, despite rigorous, need-it-or-not, periodic maintenance.

A safety device that can't be counted on 100% of the time is thought by many to be a greater hazard.

 

[DeadDiverFL]

I still use a "Calypso J" first stage that has a built in reserve for some types of diving like metal detecting or fossil hunting in shallow water for visibility problems caused by fanning the bottom for goodies and I can eliminate the HP hose and my bulky console that ends up dragging in the mud. I make sure to check the position of the lever periodicaly during my dive so it's in the correct position. Most of the time I'm metal detecting off the beach in about 5' of water and when I run low on air I just stand up and walk to shore. For any other type of diving I use a SPG.

 

[oxyhacker]

The J valves stopped being made because no one was buying them anymore. Actually, the hung around much longer than most people realize - Beuchat and Sherwood were still listing them into the mid-90's but you got to wonder how many they sold since there were zillions of used ones around that everyone was trying to get rid of.

Is is commonly said that the SPG made the reserve valve obsolete, but the near universal adoption of the octopus/safe second probably had just as much to do with it since they provided an actual backup, where the SPG just gave a warning.

 

[captain]

I believe the J valve is still being made and is available from Mar Vel. OSHA requires one in some commercial diving situations.

29 CFR 1910.424(c)(4) and (c)(5). Each SCUBA diver is required to have: (1) a diver-carried reserve breathing-gas supply that consists of a manual reserve (J-valve), or (2) an independent reserve cylinder that has a separate regulator or that is connected to the underwater breathing apparatus (see 29 CFR 1910.424(c)(4)). The valve of the reserve breathing-gas supply must be in the closed position prior to the dive (see 29 CFR 1910.424(c)(5)) to ensure that the air reserve will not be depleted inadvertently during the dive.

 

[Sam Miller III]

....

They got the nickname from the USD catalog number - the non-reserve tank valve started with the letter "K", and the reserve valve started with "J".
... James

~~~~~~~~~~~~~~~~~~~~~~~~~

Name came from the bin they were stored in at US Divers. Later they were listed in the US Divers catalog as J valves along with the K & R valves, etc.

Rene preferred to keep the inventory control process simple...

sdm

 

[Sam Miller III]

The J valves....

Is is commonly said that the SPG made the reserve valve obsolete,...
QUOTE]

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

MarMac, a Northern California company produced and marketed the first SPG in the very early 1950s only a few years after the introduction of the Aqua Lung to the US.

It met with limited sucess

The first universal adaption of the SPG was on the Sportsways units, first intoduced in 1958.

The SPG has been around a long long time...

sdm

 

[fdog]

~~~~~~~~~~~~~~~~~~~~~~~~~

Name came from the bin they were stored in at US Divers. Later they were listed in the US Divers catalog as J valves along with the K & R valves, etc.

Rene preferred to keep the inventory control process simple...

sdm

That is the coolest piece of trivia I have picked up lately - thanks! Obviously you were closer to the source than I was back then...kinda cool to see where the catalog number came from.


All the best, James