I removed the "grate" from my shower drain cover for cleaning and saw that the cover/grate combination was not sealed into place. It sits low enough that it is flush with the tile, but I was able to lift it out with no resistance. Below there are pebbles, which I believe is something like a weep hole? I don't see any leaks so far. My question is, should I seal this cover/grate combo to the structure below and next to it, and if so, with what kind of product?