I think thats called bouncing. I think it has something to do with the pressure in the pipe slowly building up, this causing it the syphon to slow down slightly, as the pressure build it reaches a point where there is enought pressure to remove some of the trapped air. I think thats whats going on. Or something to the same affect.*KrAmEr*;870368; said:I think my overflow is getting air trapped in it or something because the flow of it keeps slowing down then the water level in the tank will rise to about 1/2" below the top of the tank the it will start siphoning really qiuckly until it gets back to the top of the intake, it's kinda scary.