I am 6 months into this hobby and am learning as I go with all the advice here. I have a 54 gal. corner tank and I am having trouble with my KollerCraft TOM RP3 Overflow Box anti siphon feature suddenly quit working. Luckily I found out while doing a water change. I hope I can explain this. There is a tube on the top that connects the 2 chambers. With the pump turned off, I can pull on side of that off and the siphon stops. Any idea what causes that?