The real story on a discredited practice

Compared with diving as a whole, cave diving isn’t just tiny; it’s downright minuscule. Despite this, few activities have had as much impact on the sport as cave diving has. Examples include:

  • Sidemount.
  • The backmount configuration nearly all tech divers use.
  • The return to black masks.
  • Passing the long hose.
  • Frog kicking, modified flutter and helicopter turn.
  • Learning entry-level dive skills while neutral.

Perhaps the greatest impact we’ve had on divers everywhere is getting them to abandon the potentially deadly practice of turning open valves back a quarter turn. Granted, we’ve yet to get every diver and every instructor on board with this. However, with organizations like DAN backing us, the trend is definitely in the right direction.

Why all the way?

The practice of cave divers turning valves all the way on began with Sheck Exley. It stems from an incident which took place nearly 50 years ago.

Sheck was diving at Peacock I. In those days, the passage leading to the main-line warning sign wasn’t worn away as it is now. In fact, it was a rather tight squeeze.

On this particular day, Sheck found himself at 15 m/50 ft, upside down and wedged between two rocks. As he breathed harder, he found himself starved for air. The harder he breathed, the worse things got.

According to Sheck, he nearly died. Fortunately, he managed to free himself and surface. Exiting the water, he diagnosed the problem.

What he discovered was this: As he’d been taught, before the dive, he opened his valves all the way then backed off a quarter turn. Or so he thought.

What he’d actually done is close the valves all the way and open them a partial turn. In shallow water, his regulators breathed just fine. At depth and breathing hard, they just couldn’t deliver enough air.

If you’re among those who have no difficulty telling clockwise from counterclockwise, you may wonder how anyone could mistake this. Apparently, though, some people have a sort of dyslexia when it comes to right and left. And let’s face it: If someone with Sheck’s experience could have this problem, anyone can.

Having experienced how deadly quarter-turn-back could be, Sheck decided the NSS-CDS would only teach all-the-way-on. As more open-water instructors learned to cave dive, word of the danger spread. As more training agency staff members learned to cave dive, word spread even faster.

Today, with DAN and several major training agencies denouncing quarter-turn-back, it’s a tough position to defend. Still, some people try.

Valve damage?

For years we told divers leaving a valve turned all the way on would damage it. While this may have been true of early scuba valves, it hasn’t been so for decades.

Make no mistake: Forcing a valve all the way open will damage it. So will forcing it all the way closed. Gently turning a valve all the way on or all the way off, stopping at the first sign of resistance, does nothing.

Still, as with so many other things in diving, once a practice becomes ingrained in some instructors’ minds, getting them to change can be impossible. Worse, when instructors don’t understand the why behind an outmoded practice, they will invent bullshit reasons to justify their position. Reasons which have no basis in fact.

You already know the claim of valve damage is pure BS. Even were someone to forcibly turn an already-open valve in the wrong direction, the consequences of doing so pale compared to the risks inherent in diving with a partially-open valve. To the best of our knowledge, valve damage has never killed anyone. Diving with a partially-open valve has.

Let’s look at some of the other BS claims.

Dissimilar metals

Among the more credible explanations comes from the staff at Scripps Oceanographic Institute. They thought this might be the explanation.

The earliest tank valves from US Divers used a combination of aluminum and brass. Supposedly, US Divers cautioned against leaving valves fully open as doing so would cause the brass to come into contact with the aluminum. The resulting galvanic action might cause the metals to stick together. In any event, most valves made since 1955 have been solid brass.

A standard of practice?

Some instructors claim it’s a standard of practice throughout several industries never to leave a valve fully open. This is at least partially true. However, when it is, it is usually due to the nature of the industry, not the prospect of valve damage.

For example, many welders will tell you never to open an oxygen bottle any more than required to get an adequate rate of flow. Why? If there is a fire, you must be able to shut off the oxygen supply as quickly as possible.

In general, any field in which it’s a standard of practice not to open valves all the way doesn’t deal with breathing gas.

Divemaster check

Another explanation I’ve heard goes something like, “It’s so the divemaster can reach over to ensure your tank is turned on before you jump in the water.” Of course, were this to happen, it wouldn’t matter if your valve was fully turned on or partially turned back. At least it wouldn’t if the divemaster possessed sufficient intelligence not to force things.

What’s concerning about this explanation is there are reports divemasters have turned divers’ air all the way off thinking they were turning it on. Thus, this “divemaster check” explanation sounds more like made-up BS than actual fact.

Valve freeze

By far the most absurd “explanation” we’ve heard came from a diver whose instructor told him, “In cold water, a free-flowing first stage could cause a valve to cool to the point it would freeze up as well.” Let’s think this one through:

  • If a fully-open valve could freeze up under these conditions, a partially-open valve could freeze up as well. I’ve never heard of this happening. Have you?

But let’s say leaving the valve partially closed would let you shut off the gas supply to a runaway first stage. What would you gain?

  • If you are diving a single cylinder with a K-valve, you just shut off your sole gas supply. No longer are you running out of gas, you are out of gas.
  • If diving an isolation manifold, you shut off the isolator and switch to the unaffected side of your doubles.
  • If diving sidemount, you switch to the other bottle. End of story.

Again, damaged valves don’t kill. Partially-open valves do.

Finally, an explanation which makes sense

A reader named Anthony posted this response to the 2013 article The Quarter Turn That Kills on

“The reason there are so many ignorant instructors out there is because opening a valve all the way and then backing off a quarter turn is the proper practice only for valves which have steam moving through them.

“I worked for many years at a coal-powered power plant. There we followed the quarter-turn-back procedure. This is because valves were initially at ambient temperature. As anyone who paid attention in high school know, heated objects expand.

“If a valve is open all the way, then heated to a few hundred degrees with super-heated steam, the valve stem, seat and packing expand. This binds the stem. The only way to close the valve is to allow it to cool.

“This isn’t realistic in an emergency, when you might need to shut off a valve right now. Under these circumstances, your only recourse might be to use a pipe wrench to turn the stem. Unfortunately, this often results in breaking off the valve stem. Then you most definitely won’t shut the valve until the furnace/turbine shuts down.

“Divers don’t super-heat their valves. Consequently, there’s no need to turn them back one-quarter turn. The valve isn’t going to get hot enough on your back to expand the internal parts and bind against the housing.”

Given the fact steam valves have been around longer than almost any other kind, this explanation seems credible.

Go with the experts

DAN’s Dr. Peter Buzzacott has posted no less than three articles on the DAN website pointing out the dangers of not turning valves all the way on. He would know. Among his jobs at Divers Alert Network is monitoring accident statistics to discover what really gets divers killed.

Of course, we’re preaching to the choir here. If you are a cave or technical diver, you probably gave up the quarter-turn-back nonsense some time ago. Still, if you must argue with those who ignore the facts, you now have a new weapon. Just ask how long they’ve been breathing super-heated steam.

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