A zero pressure drop water heating system comprising a cold side conductor having a receiving end and a closed end; a hot side conductor having an exit end and a closed end; a pump; a bypass conductor having a first end, a second end and a bypass valve, wherein the first end is adapted to the receiving end and the second end is adapted to the exit end; at least one heat exchanger having a flow valve; a heat exchanger inlet temperature sensor disposed on the inlet of one of the at least one heat exchanger; an outlet temperature sensor disposed at an outlet of the at least one heat exchanger closest to the exit end; a system outlet temperature sensor disposed on the exit end and a system inlet temperature sensor disposed on the receiving end.