Screw it, how hard can it be? The Importance of Correct Tank to Valve Compatibility

SAGE SULARZ   Jul 19, 2023

Understanding your gear is one of the most valuable skills a diver can have. As technology advances, new options come onto the market and older models should be carefully examined to ensure function and compatibility. A recent tragedy involving the death of a European diver resulted from a simple valve-to-cylinder mismatch. Knowing the facts could prevent potentially dangerous situations from arising on your own future dives.

 

Prior to 1958, U.S. SCUBA cylinders were most commonly ½ inch National Gas Tapered (NGT) threads. Over the next decade this slowly transitioned to use of parallel ¾ inch National Pipe Straight Mechanical (NPSM). The next major change occurred in 2006 when International Standards Organization (ISO) cylinders were accepted by the U.S. government. Today a diver is most likely to encounter either the ¾ inch NPSM commonly with 14 threads per inch or the M25x2- ISO with 12.7 threads per inch when diving in the U.S.