Airworthiness Directives; Boeing Model 737-100, -200, -200C, -300, -400, and -500 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes, that requires replacing the existing pressure relief valve on the potable water tank with a new, improved pressure relief valve, which is made of stainless steel and is non- adjustable. For certain airplanes, this AD also requires modification of certain piping to re-locate the pressure relief valve. This action is necessary to prevent rupture of the potable water tank during flight of the airplane, which could result in structural damage to the airplane and its inability to sustain flight loads. This action is intended to address the identified unsafe condition.