Primary/secondary piping is a way to achieve hydraulic separation by connecting multiple hydronic circuits with their own circulators to prevent interference. Using a pair of closely spaced tees is a common method to achieve this.

If you’re anything like me, the first thing that comes to mind when you think about variable speed circulators is 1970s rock band Supertramp. No? Okay, maybe you’re not like me. Either way, allow me to elucidate.