Which valve type is preferred for diving tanks?

The J valve is preferred for diving tanks primarily because it incorporates a reserve feature that allows divers to manage their air supply more effectively during dives. This valve type provides an additional safety margin by enabling a diver to reserve a portion of their air, ensuring that they have enough gas to safely return to the surface even if they haven't been monitoring their air consumption as closely as they should.

In practice, the J valve's reserve feature activates when the tank reaches a certain low-pressure level, providing a warning that it's time to ascend. This can be especially critical in scenarios where a diver might be at depth and unaware of their remaining air supply. While the K valve is also functional and can provide an adequate safety measure, it does not have this built-in reserve system, making it less favorable in situations where air management is crucial.

Overall, the adoption of J valves has been standard in many diving practices because of this added safety advantage, which emphasizes the importance of having a reliable and effective means of monitoring and conserving air underwater.