I am planning to put an open loop system in my home. It is a 4 ton. I have very light and gravely soil. I have a pond 600' from my house that is the water table. I was going to discharge the water back to the pond. The question is, what size line do I use and what type? Do I need a check valve? I was going to keep the line below frost level and discharge it below freeze point in the pond. Is 1 1/4" black plastic sufficient?