PURPOSE: To suppress the cost and lessen the space for installation by furnishing inside a cylinder a spring of shape memory alloy for applying a forward stroke force to a piston, upon sensing the temp. of warm water, and a bias spring to apply a return stroke force.

CONSTITUTION: During the standby mode for warm water supply, a bias spring 15 deforms a spring 14 of shape memory alloy and draws a piston 12 toward itself, and the piston is held in a position above the inlet 11a, while the outlet 11b is opened by a valve 16. The spring 14 pressurized by warm water is restituted to the compressed coil condition as its memory shape, and overcomes the bias spring 15 with the recovery force to draw the piston 12 quickly toward the outlet 11b. The piston 12 making forward stroke quickly toward the outlet 11b blocks the inlet 11a and opens the outlet 11b, and the warm water in the cylinder 11 is pressurized. At an appropriate speed, the warm water is fed to a drinking cup 5 from the discharge hole of a supply pipe 3.