Post by John C Ratliff on Jan 19, 2004 21:08:33 GMT -8
For those who haven't seen this, it is a good illustration of how to clear a two-hose regulator. It comes from the Councli for National Co-Operation in Aquatics (CNCOA)'s book, The New Science of Skin and Scuba Diving. There are a few comments that are in order, however. First, this is for a flooded hose without non-return valves in the mouthpiece. You can see in the illustration that there's more water in the hose than can be held by the mouthpiece. This technique, whether you have non-returns in the mouthpiece or not, will rid the exhalation hose of water.
Why would they show a technique that assumes no non-returns in the mouthpiece? Well, they (mouthpiece non-returns) were invented after the hose/mouthpiece system, and in response to flooded hoses. The USD "T" mouthpiece was the second to incorporate these, and they were called "Kleer-EZ Mouthpiece and Hose Assembly" by US Divers Company. Prior to that, the Hope-Page mouthpiece was used, and at times substituted for the US Divers original mouthpiece, which was smaller and lacked non-return valves. Healthways adopted the Hope-Page system for their Scuba regulator in its original design. Other early regulators also used the Hope-Page system with non-returns.
Why would one not use a non-return? Well, they increase breathing resistance. Also, in the U.S. Navy School for Underwater Swimmers, they insisted that we remove them so that our training could be more "realistic." (The instructors were saddists; we clandestinely put them back in).
There are other ways of clearing the mouthpiece. Simply holding the mouthpieces up above the regulator and inducing free-flow will do a good job, and any water can be cleared in a roll.