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Scuba Diving by Dennis K. Graver, 1993, page 105 paragraph titled: The Reserve Valve. 1) Quote: A J-valve (the valve was listed as Item J in the first equipment catalog) maintains a reserve of air to permit normal ascent. 2) Quote: The reserve lever on a J-valve can create problems. If the lever is in the incorrect position (down), the valve will not maintain a reserve. If you fail to put the reserve lever in the up position before a dive, or if the lever is bumped during a dive, you might rely on a reserve of air that will not be available. 3) Quote: During the filling process, the reserve lever of a tank with a J-valve must be in the reserve position (down). If the lever is in the up position when the operator applies high-pressure air to the tank valve, the seat of the reserve valve will be damaged. 4) Quote: Because J-valves cost more than K- valves to purchase and service, and because of the problems mentioned, the J-valves popularity has declined steadily over the years. Apparently there are a few exceptions! ;-)) The Essentials of Deeper Sport Diving, John Lippman, 1992, page 197 paragraph titled: Cylinders and Valves. 1) Quote: A "J" valve should be removed and replaced with a plug. The spring within the valve mechanism eventually fatigues and this will reduce the amount of reserve air a diver might expect. "J" valves may jam at times and can unknowingly be knocked "on". 2) Quote: Taping a "J" valve down in the open position will not guarantee that the inner mechanism will remain DEACTIVATED. Caps are mine. Joan Coval, wreck dive, June 1995, experience titled: ??!!?!?!??? I had a rental tank with a J-valve installed. This was my first experience in the use of one, so as a precautionary measure the valved was enable to the down position as I was used to monitoring tank pressure and was not used to flipping valves and such at depth. My dive partner was also advised and was knowledgeable with J-valves and said operation of same. Into the water with 3100 psig tank pressure. Some time into the dive at 80 fsw I noticed that my inhalation resistance was increasing and observing my tank pressure gauge, the needle would dip from a maximum tank pressure of 1500 psig to approximately 700 psig on each and every inhalation. At this time I notified my partner that I was heading onward and upward and we began my ascent to 10 feet where it is my customary procedure to hang for 5 minutes and then surface. Us older people need all we can get of hanging out after any dive :)) Any way I was intrigued with what was going on and I just observed the phenomena and after 5 @ 10 I then we both surfaced. On the boat I verfied that the valve was in the original position which was down. And yes, it was later verfied that the valve malfunctioned. My lesson is; I don't dive with J-valves on my tanks. Besides, twisting just one knob is more my speed! -Joan-
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