Why do you make such a long sock pipe? I would think that it only needs to be under the water below the frost line plus a couple feet for safety. With the way you have it, your sock pipe could freeze if your pond was low. This would only be a problem when the ice level is below your sock level.Using a solid pipe that is under frost line coming up near the bottom of the pond with a pile of rock on the end may work better if you live in a area that has a lot of droughts. For those of us that work on a very low budget you could use a lot less rock.
I like the idea of getting the bad water out first. Any idea how much water would come out a 4 inch pipe?
