Hello pumper’s forum, I recently started pumping for the first time 2 weeks ago and am very impressed by its potential. I’ve only been pumping for 2 weeks but have gained a lot of knowledge from this forum. I stuck to exclusively air pumping for the first week and took it slow to “break in” my penis per se, and then the following week I tried water pumping. From my observations, water pumping produces significantly more expansion with less stress on the penis. My theory is that fluid pumping decreases penile surface stress via two factors: a more equalized distribution of pressure, and more actively the compressibility of water (or lack thereof) which directs all of the vacuum pressure to penile expansion. I am not an engineer, so my knowledge of fluid dynamics and vacuums is limited (or non existent), but due to water’s ability to resist compression at normal temperature [0C-45C), that means its volume stays relatively unchanged when pumped. What does change instead is the pressure acting on the penis as inner pressure expands it outwards. Air on the other hand will expand as vacuum pressure is applied which seems to apply more surface pressure/stress to the tissue via a pulling sensation on the skin.
With water, I warm up by pumping slowly with warm water for 5-10 minutes, and then switch to cold water for 20 minutes. I notice greater expansion and less edema with cold water. I believe this is because as pressure is applied to the water, it heats it up while also heating up the surface tissue of the penis (this occurs with air as well) which stresses and bruises the skin. Cold water cools the tissue under expansion. This is just my theory from playing around for 2 weeks. I hope somebody with a scientific background can figure out what’s going on. All I know for sure is I achieve an extra 1/4” with water versus air, and another 1/4” with cold water versus warm in regard to LUV with fewer negative effects.