October: Tank Valves

A veteran diver experienced a breathing issue after exiting a commercial boat with his dive buddy. All was good until he reached 70 feet of depth where breathing became difficult.  In addition to difficulty breathing, he noticed his pressure gauge was dropping significantly while he inhaled and then recovering to full tank pressure when he stopped inhaling.

He signaled his buddy and they began an orderly ascent to the surface. 

Once safely back aboard the boat, he explored his equipment problems and found that his tank valve was very nearly closed. He was certain he had fully opened his tank valve before diving, so how was it that it was nearly closed during his descent?

The dive buddies began asking some questions aboard the boat. They learned there was a fairly inexperienced mate who admitted that he had manipulated the air valve without advising the diver that he was doing so. The mate had apparently closed (rather than opened) the valve and then when the valve hit the stop he had turned it back a quarter turn. This condition had allowed the diver to begin his dive without apparent issues.

We can learn at least 3 things from this incident:

1. It’s very important to understand that a tank valve closes when turned clockwise and opens when turned anti-clockwise.  You may recall the rhyme: “Righty tighty, lefty loosey” to help you recall how the valve stem functions.

2. You should never manipulated another diver’s tank valve without discussing it with him or her.

3. It might be wise to always turn your tank valve to the full on or full off position, rather than turning it fully on and then backing off a quarter turn as is sometimes recommended.

Be Safe, Dive Safe

Dave Wills