Will be building my reef tank soonish and I got it used. Want to re pipe the return line. It is a 3/4 inch pvc line, Can I do part of it flexable tubing? I know I want to put in a check valve but what else do I need. Would go over the top of the tank as there is no return line drilled. Only the drains are drilled. I am using a DC pump so no need for a valve on the return line.