To protect a uniaxial pressure regulator for tap water and a solenoid valve installed at the inlet of a device such as an ice making machine against damage by a high water pressure in a water hammering.

The valve seat assembly 7 of the uniaxial pressure regulator for tap water in which a stopper C limiting a stroke is fitted to a plunger 2 is movably installed on the upstream side. Thus, even if the water hammering occurs between the pressure regulator and the solenoid valve installed at the inlet of the ice making machine, a food machine, and a water heater, the solenoid valve can be prevented from being damaged by sliding the valve seat assembly 7 to the upstream side to escape the high water pressure to the upstream side.