[pierremcalpine]

Originally Posted by canis

Still a bit confused. You press in the diaphragm, and go to put it back on the reservoir, it pops out again just in time for you to reach the fluid where it hits the surface and displaces a load all over the sides. I'm not getting this, am I?

If the rubber thingy is installed snugly in the cap itself, when pushed inwards it should stay put without issue.