A zero pressure drop water heating system comprising: (a) a cold side conductor comprising a receiving end and a closed end; (b) a hot side conductor comprising an exit end and a closed end; (c) a pump; (d) a bypass conductor comprising a first end, a second end and a bypass valve disposed between said first end and said second end of said bypass conductor, wherein said first end of said bypass conductor is adapted to said receiving end of said cold side conductor and said second end of said bypass conductor is adapted to said exit end of said hot side conductor, said bypass valve is a modulating valve and said bypass valve is configured for control of a forward flow from said cold side conductor to said hot side conductor through said bypass conductor or a reverse flow from said hot side conductor to said cold side conductor through said bypass conductor; (e) at least one heat exchanger comprising a flow valve; (f) an inlet temperature sensor disposed on an inlet of said at least one heat exchanger; (g) an outlet temperature sensor disposed on an outlet of said at least one heat exchanger closest to said exit end of said hot side conductor; (h) a system outlet temperature sensor disposed on said exit end of said hot side conductor; and (i) a system inlet temperature sensor disposed on said receiving end of said cold side conductor, wherein said receiving end of said cold side conductor is connected to a cold water supply manifold, said exit end of said hot side conductor is connected to a hot water supply manifold, said pump generates a flow through each of said at least one heat exchanger; said bypass valve, said flow valve of said at least one heat exchanger, and said pump controls said forward flow that tempers a flow exiting said exit end of said hot side conductor when a temperature indicated by said inlet temperature sensor exceeds a temperature indicated by said system inlet temperature sensor, said bypass valve is controlled by modulating said bypass valve, said flow valve of said at least one heat exchanger is restricted to enable an increased forward flow through said bypass conductor, to result in a flow through said zero pressure drop water heating system having a pressure drop of zero at said exit end of said hot side conductor; and, when a temperature indicated by said system outlet temperature sensor falls below a temperature indicated by said inlet temperature sensor, said bypass valve, said flow valve of said at least one heat exchanger and said pump control said reverse flow that supplies at least a portion of a recirculation flow through said at least one heat exchanger when the capacity of said pump exceeds the demand, said bypass valve is controlled by modulating said bypass valve, said flow valve of said at least one heat exchanger is enlarged to enable an increased flow from the cold side conductor to the exit end of the hot side conductor through the at least one heat exchanger to increase the temperature of the water mixture exiting the exit end of the hot side conductor, to result in the hot water demand being met at a higher efficiency, the arrangement being such that said bypass valve, said flow valve, and said pump control flow through said zero pressure drop water heating system to result in a pressure drop of zero at said exit end of said hot side conductor. (a) a cold side conductor comprising a receiving end and a closed end; (b) a hot side conductor comprising an exit end and a closed end; (c) a pump; (d) a bypass conductor comprising a first end, a second end and a bypass valve disposed between said first end and said second end of said bypass conductor, wherein said first end of said bypass conductor is adapted to said receiving end of said cold side conductor and said second end of said bypass conductor is adapted to said exit end of said hot side conductor, said bypass valve is a modulating valve and said bypass valve is configured for control of a forward flow from said cold side conductor to said hot side conductor through said bypass conductor or a reverse flow from said hot side conductor to said cold side conductor through said bypass conductor; (e) at least one heat exchanger comprising a flow valve; (f) an inlet temperature sensor disposed on an inlet of said at least one heat exchanger; (g) an outlet temperature sensor disposed on an outlet of said at least one heat exchanger closest to said exit end of said hot side conductor; (h) a system outlet temperature sensor disposed on said exit end of said hot side conductor; and (i) a system inlet temperature sensor disposed on said receiving end of said cold side conductor,