Abstract: A water temperature regulator having a closed container that is provided with a cold-water inlet pipe and a hot-water inlet pipe having flow control connected thereto for introducing cold and hot water, respectively, into the container at a desired flow rate, a discharge pipe for guiding water in the container to an external water storage, at least one water service pipe for guiding water in the container to at least one water supply outlet, such as a showerhead or a faucet, at least one control for controlling open/close of the discharge pipe and of the at least one water service pipe, and a water temperature indicator for showing a temperature of water in the container. Instead of being drained, water introduced into the container that has not reached a desired temperature is discharged to and stored in the water storage for reuse later without being unnecessarily wasted.