ok, the jokes on me! How the HE** do you prime a pump??? Every time I put water in it primes to the suction end-but of course comes out! So, if I start the pump-it is dry! The pump is above the water in the sump-hooked up to the skimmer. If I put water in the skimmer (going backwards) it would have to fill the skimmate collection cup to the top...the directions mention a "foot valve" . Do you know what that is? Please help, this is really driving me nuts!!!