Meng_Tze:Are you kidding me? What can and has been seriously transmitted by using the same mouthpiece? When you rent gear, do you put on a new mouthpiece?
It think things can be drawn too far and too much in the cleanliness areas.... this being one of them. Have you thought about where you use this equipment in? Analyze the pool water and the sea water..... I bet you they are FAR dirtier than the mouthpiece...
If you are dipping divers like tea bags and using the company equipment, it makes the customer feel better if you swish the parts they stick in their mouth in some sort of cleaner looking solution.