System for stopping water flow in water use installations

System for stopping water flow in water use installations, meant to prevent the outlet of cold water while heating the water from the corresponding boiler to the faucet of use, with the resulting savings in cold water and energy in the operation of the boiler while heating said water, characterised in that between the hot water pipe (4) and the cold water pipe (5) connected to the heating boiler (8), and before or forming part of the faucet (6) itself where water is demanded, a thermostatic bypass (1) is provided through which the water runs in a closed circuit along the hot water pipe, the bypass itself, the cold water pipe and returning to the boiler (8), driven by the corresponding pump (9) fitted in the hot water pipe (4), so that opening and closing the faucet (6) in the hot water position will start this recirculation of water through the bypass until a preset temperature is reached, at which time the thermostatic valve of the bypass is closed and the hot water in the pipe (4) can be used directly when opening the faucet (6).