We have a heat pump in line with our returns, after our filter. When I closed recently of course I blew the return lines out, and I assumed that plus opening the drain plug should have taken care of the heat pump as well. Well, the drain plug on the heater is a sort of springy, retained drain plug, which, being unfamiliar with, led me to get the manual out. Then I found the manual says to disconnect the inlet and outlet pipes for winterizing. We do have unions there (although I currently have no tool big enough to grip them) but I don't see the need. Am I wrong? Should I really disconnect the heater there?