Well, my niece and her husband just bought 15acres with about a 3acre (when full) pond! Pond is currently about 6' low do too an old 6" cast iron overflow pipe. He asked for my help to stop the leak so it can fill back up. After brain storming I came up with the idea of placing a half inflated socer ball into the intake of the pipe and inflating it-well after several attempts of chasing the ball as it exited the discharge side we finally got it stopped! We then poored sac creat on top of the inflated ball below the water line.This thing is so rusted-and crumbling above the water, beyond salvage!! What now! I plan to put in a syphon system since it is so low-but how do we permantely disable this old pipe without draining the rest of the pond. There are still fish in it and they can not afford restocking! They are young and this is there first home-My idea is: Place a larger PVC pipe around the existing riser portion and fill with concrete-Then pump crete from the discharge side aswell! What yall think?