I hired a grader today to start my 1.5 acre pond in 2 weeks. We roughly have 55 acres of watershed and he was saying we need a 24 inch pipe. That sounds big to me. Also, what type of system would you guys recommend? Everyone seems to go with a syphon system, but I want to be able to drain it if I need too. Sorry for the silly questions. I am new to all of this. Thanks in advance for your help!