My pond is an excavated hole in the ground (no Dam). I want to make a culvert overflow so that when the pond reaches a certain level it will start to run off. Is it possible to put an elbow on the pipe to take the water from deeper in the pond? keep in mind there is little difference in the elevation from the level of the main pipe to the outflow. I was thinking that once the pond level reaches the horizontal pipe it would flow out and the pressure from the pond water would keep the up tube full to the same level as the pond itself. Thanks for your help.