without a bead on the end of the pipes, hoses can slip off. I've had good pipe staying power by carving 2 or 3 shallow grooves around the pipe's circumference near the end where the clamp will sit. Dragging a sharp hacksaw (not sawing) around the pipe will do this nicely. Also, a very, VERY thin smearing (.001-.002" thin) of RTV silicone between the (clean!) pipe and hose mating surfaces helps glue things together.