I cannot for the life of me get my 3 gallon, plastic waterer to work properly. I fill it up through the top (with the little white cap over the little hole where the water comes out)...then I screw on the black screw top on the top of it, but when I open the little white cap to let the water out into the "pan" it comes out with a tremendous gush and just doesn't ever stop!! Overflows every time. Am I doing something wrong? Or can these things possibly be defective? After so many tries and not getting it to work, I'm starting to feel like I'M defective!!