Pond Boss Forums POND CONSTRUCTION Building a dam Washout around exit pipe on new pond... what to do

Once the pipe is full and not pulling air from the inlet (given enough head on the dam and installation of an anti-vortex device), the increased drop after adding the pipe will probably increase flow considerably rather than decreasing it. That assumes you do not install a T or Y (or any other way for air to get in). That is why my pond pipes all slope down as much as possible leaving the pond. Think about it like starting a siphon and what happens to the flow rate as you drop the outlet side of the tube. The weight of the water dropping actually pulls water into the pipe. Its like having a bigger pipe without the added cost.