I recently purchased a wash that has 2 on-demand water heaters that are piped to a storage tank with a thermostat that turns on a circulation pump to cycle water throught the 2 on-demand water heaters when the temperature drops. This is a small wash with 2 selfserve bays and 1 automatic. My question is: Is the storage tank necessary? It seems to me if you are going to store the water in a tank anyways its the same thing as a conventional water heater. Does anyone use on-demand water heaters without the storage tank?