To sufficiently magnetize water supplied to a cock.

A water injecting pipe 4 rising from the ground is connected to an inlet 2 of a water feeding tank 1 provided on a building, and a water distributing pipe 6 provided with cocks 5 is connected to an outlet 3. The water distributing pipe 6 and the water injecting pipe 4 are connected to a return pipe 7, and a pump 8 returning a part of the water sent out from the outlet 3 to the inlet 2 and a magnetizing instrument 9 for generizing a magnetic field inside the return pipe 7 are provided at the return pipe 7. A part of the water sent from the water injecting pipe 4 to the water feeding tank 1 is circulated through the return pipe 7 in accordance with a driving of the pump 8, and the water is sufficiently magnetized and supplied to the cock 5 since a circulating flow passes through the magnetizing instrument 9.