So I am putting my 110 together and when I try to click the U-tube into the impeller housing, it just sits on top with a little flat piece of black plastic and won't let me "click into place." Do I just let it sit on top without giving it any pressure or should i try to push it on? I just won't want to break this thing... The directions are pretty crappy because it doesn't show this black plastic piece on there. HELP!



