Mike nailed it dead on. Closed loops are expensive to install, and difficult to maintain (unless you use tons of true unions ballvalves which make it even more expensive). IME you cannot get the wide of flow of tunze stream through a closed loop, unless you build a completely ridiculous one like Greenmako's.
Hopefully Brian (Greenmako) will chime in and tell you a ballpark figure for his closed loop because it was way more expensive than I had thought initially.