Summary
This document revises an earlier proposed airworthiness directive (AD), applicable to certain Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes, that would have required 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, that earlier proposed AD also would have required modification of certain piping to re-locate the pressure relief valve. For certain other airplanes, this new action would revise the earlier proposed AD by correcting procedures for performing the proposed replacement of the pressure relief valve. The actions specified by this new proposed AD are intended to prevent rupture of the potable water tank during flight of the airplane, which could result in structural damage to the airplane and inability to sustain flight loads. This action is intended to address the identified unsafe condition.