I was wondering about bulkheads. Right now. I have 3/4" flex tubing running from my sump to my tank(using a 3/4"barbed bulkhead). I want to change to PVC. Am I right in saying that I need to change that bulkhead to a 3/4" slip bulkhead? I want to make sure I get the right one. Does the PVC slip inside the bulkhead?