Editor's Note: Some of the formulas referenced in this article could not be reproduced online. Please see print edition for these formulas.
Over the years, I've noticed an innate tendency in people just learning about hydronic heating. When given a group of piping components such as valves, multiple heat emitters, pumps and so on, most folks want to connect them together in a series circuit. I suppose that's natural, considering they understand that water going out into the distribution system also has to come back.