Quarter Turn Back - Nope!

Greg Galford   Jun 29, 2024

If you were trained more than ten years ago when you opened your tank valve, your instructor told you to turn it back closed quarter of a turn. Why? Generally it was explained the valve wouldn’t “freeze open” or that it was “better for the valve”. Neither one of these is true based on the design of valves, but the reasons seem to persist.

What are the issues with the quarter turn back? There have been a large number of documented instances where the valve has been closed and then opened quarter of a turn back. This provides enough air at the surface, but not enough at depth leading the diver to feel air starved. The diver can quickly come out of this by controlling breathing and by ascending to lower the required amount of air. Although the situation doesn’t sound serious a number of folks have panicked, or in the extreme case of Sheck Exley while cave diving, almost drowned. I have personally seen people who were checking other people air during the buddy check turn it all the way off and back on a quarter of a turn.

Today, we teach a valve should either be all the way open or closed, never in between.

A few good habits to get into:

• When checking your gear on the boat after setting up, either leave the valve all the way open, or if closing it, drain the regulator. This will make sure that you don't jump off the boat with a tank valve off since you won't get any air from your regulator if it is off.
• Test breath your regulator before going diving while watching your pressure gauge. If the tank valve is closed, or partially open, the needle or display will drop (and in the case of a valve that is partially open will recover).
• When doing your buddy check to make sure they have their air on, leave it all the way open and don't turn it back. After somebody checks your valve, test breath the reg.

Greg