I have 2 electric hot water heaters that have been connected to heat recovery unit of off heat pumps. Heat pumps have been replaced, and I want to remove the heat recovery unit out of the circuit. The current flow from the heat recovery unit comes into the bottom of tank 1, hot from tank 1 to bottom of tank 2, "cold" from tank 2 to heat recovery unit. What is the most efficient way to plum the two hot water heaters together?