Pond Boss Forums POND CONSTRUCTION Renovating a Pond or Lake? Adding an elbow to change overflow to vertical ??

You probably already thought of this but just in case...I would spend a little time thinking about how I want to plug the end of the horizontal part of the T. An 18 inch pipe has a cross section of around 250 sq in. If you decide to lower the pond level from the vertical of the T to the horizontal, I would remove the horizontal plug while the drain pipe is still full. If you let the pond drain to where the vertical is not overflowing, level is still above the horizontal and the drain pipe goes empty, there could be a few hundred pounds of water pressure trying to keep you from removing the plug from the horizontal....In other words, I would think of a way to plug the horizontal that can be removed even if there are a few hundred pounds against the plug.

Just my 1 cent...