The present disclosure is directed to a backwater valve assembly comprising a main valve body, a flapper sub-assembly, and a cap. The main valve body has an inner wall that can define a recess into which the flapper sub-assembly can be removably secured. The flapper sub-assembly includes at least one flapper element that can pivot between an open position, in which the flapper element allows fluid to flow through the backwater valve assembly, and a closed position, in which the flapper element prevents fluid from flowing in the opposite direction. The flapper sub-assembly can be removably coupled to the cap to allow the flapper sub-assembly and cap to be installed in or removed from the main valve body together as a unitary assembly.