I guess I'll have to go into a little more detail. First of all, the diaphram will close normally regardless of the position of the reg. What gravity has to do with it is this.
- When you exhale, the diaphram opens because the pressure in the regulator is greater than the pressure of the water, allowing the air to excape.
- At the point when your exhalation stops the diaphram is under equal pressure on both the inside and ourside of the regulator. It is during this time that a very small amount of water may leak into the regulator.
- In the normal, exhaust valve down diver swimming happily position, this water will remain on the rim of, or next to the exhaust diaphram. This is normal. When you exhale once again, this little amount of water will be expelled with your breath, and you never know it was ever there.
- In the abnormal position, as is the case of being on your back, or in a head down position, the small droplets of water that normally enter your regulator, patiently waiting to be expelled with your next breath. Are no longer where they are supposed to be, because gravity has pulled those droplets to a point away from the exhaust valve. Over several breaths this small amount of water will build to a point that they will either fall into your mouth (gravity again) or be pulled into your mouth with the rush of air when you inhale (wet air symptom).
This is completely normal, and will happen to every regulator when operated in an abnormal orientation. Some regulators may seal themselves faster than other, and may take a little longer to show symptoms, but over a short time they will. Oddly enough it is the "cheap" harder to breath regulators that will have a tendancy to be dryer when used in other than normal orientations.
Whew,,,hope I made this a little clearer. Anything more would require the explanation of low pressures around the exhaust valve rim, caused by the turmoil of air excaping, and why this in fact has a pulling effect on the water surrounding the valve,,, but I digress. :geek: