Is it normal for the expandable plug to pop out of the return fitting?Ea. year when the ice starts to melt and I have a island of ice in the center that slowly floats around on windy days it seems to pop the plug out " froze around the wing nut" and I lose a little water that I was hoping to let mother nature re-fill.I tightened as tight as possible by hand and don't really want to over kill it in avoiding some damage.It is a cone shape so I assume not a whole lot of it actually grips when expanded.