K valve vs J valve

[Rick Murchison]

Originally posted by Campana
I can't imagine someone accidentally not filling your tank cause the J valve was in the up position.

This usually happens where lots of tanks are being filled several at the time, so noticing that six tanks are filling a little more quickly than usual does escape the filler.
Like many things in life, there are two kind of folks who use "J" valves - those who have gotten the short fill, and those who will.
Rick

 

[devjr]

In the 50's, there were three kinds of valves available, the K valve, J valve and R valve. The K valve was a straight post type valve with knob on the top, the J valve, a modified post valve, had a knob on the top and reserve lever on the side; the "R" was a post valve with combined "on" and "reserve" built into a single knob on top. This unique valve had two outlets set vertically inside the teflon ring(before O rings). The smaller hole was for air supply, the other for reserve supply. Turning the knob all the way open allowed air to pass through the larger hole, thus releasing the "reserve".

By 1959, the R valve was dropped from the product line. Around this time also, a maverick inventor with the Waterlung company, developed a low profile valve with the "on" knob on the side and the reserve lever in the usual left hand side position. This is the type valve our novice friend is inquiring about.

Yes, for brevity we called the valves by their catalog letters and, in truth, I am one of those who started the practice. USD called those valves NON RESERVE, CONSTANT RESERVE and POSITIVE RESERVE. Strangely, with these new low profile designs, the valves themselves began to appear somewhat similar to their original catalog designations.

As a teenager, I had no idea, that 45 years hence, divers would not only continue to follow but extend this idiom.

 

[viperdriver]

You have a J valve. I have been diving since I was 14 years old, and am now 65 so I've seen a big change in diving equipment. I now dive with the U.S. Divers triple 30s ABS system with a Royal Aqua-Master.

The J valve is actually a very good valve to have. You hear stories all the time about divers either making emergency accents or buddy breathing because they weren't paying attention to their air pressure. The old unbalanced regulators had their advantages also, as when you were low on air the air draw would get slightly more difficult alerting you that you were running low on air. So the unbalanced regulators did have some safety advantages. I still use the J valve on one of the tanks and it is set for 500 PSI, and it has come in handy at times.

 

[herman]

Don't worry. As a part time tank monkey, I can tell you that if the valve is in the up position, the tank won't fill, at all. You have to move it down. I can't imagine someone accidentally not filling your tank cause the J valve was in the up position.



.

I have it happen to me twice, both times with the same tank jocky. First time I didn't pay attention and did not realize he had not fulled it until I had gone. The second time I was watching him closely. As he was about to stop filling my tank because "it was full", I stopped him and told him it was not filled. He snidely pointed at the 3000psi gauge....and the look on his face was priceless when I moved the reserve lever down and the tank pressure dropped to a few hundred pounds. It does happen so I try to drop my J valves off in the fill position to help prevent this issue.

 

[tridacna]

.Baaaaack to life after 14 years of deserved rest...

 

[Bob DBF]

The problem is that your SPG will read the tank pressure quite well. It doesn't know about the 500 PSI thing. So if the reserve valve is mistakenly turned on or slips on or whatever, you'll find out only when your SPG goes from 501 to 0 in one breath. If you get the spring and valve seat/pin removed - the problem goes away.

Well yes an no. You will see a large drop in pressure on your SPG when your j-valve is in the dive position ( reserve engaged ) when you inhale. When at rest, tank pressure will be shown, so the SPG will act like you have the tank valve slightly open, but it is the j-valve mechanism metering the air flow. When you get to the set point of the valve it will no longer allow air to flow. For more than you want to know about it, follow the link:
J valve behavior?

When the j-valve is in the fill position the reserve valve is held open so it can be filled. J-valves that have been disabled will be in the fill position, in the dive position the tank cannot be filled.



Bob
-------------
Still dives j-valves.

 

[viperdriver]

I have it happen to me twice, both times with the same tank jocky. First time I didn't pay attention and did not realize he had not fulled it until I had gone. The second time I was watching him closely. As he was about to stop filling my tank because "it was full", I stopped him and told him it was not filled. He snidely pointed at the 3000psi gauge....and the look on his face was priceless when I moved the reserve lever down and the tank pressure dropped to a few hundred pounds. It does happen so I try to drop my J valves off in the fill position to help prevent this issue.

I always pulled the lever down in the open position. That way I knew the tank would be filled. I did not let the tank guys touch the J valve. After filling I put the valve in the up (closed) position. That way I never had any problems.

 

[captain]

J valves are easier on the fingers when carrying tanks. All my tanks have j valves for that reason.

 

[Skulmoski]

I had a J value in the 70's. But I forget if the tank was steel or aluminum. I did not have problems with the value.

GJS

 

[drbill]

Ah, the good old days before BCDs, SPGs, octos, dive computers and all that fancy stuff (that I wouldn't dive without today!).

I dove J-valves for some time back in the 1960s and 70s. Problem was that I dove in kelp forests and the darned rod was often pulled down by getting snagged in kelp before I needed the reserve! Yet somehow I'm still alive and diving today! Imagine that...