When you see how it sticks due to the pull of the water, you'll probably not be concerned with this. If you are, then I'd think about some kind of clamp over the top of the pipe would suffice, like three quarters of a ring of 1.25" pvc that would slide on over the plastic and pinch it against the loop and hold it in place. You wouldn't need much because, like I said, it isn't inclined to move anyway.