Abstract: A grease trap having an inlet member, a discharge member, a plurality inner walls defining chambers within, and a relief member for flushing accumulated waste matter. In general order of fluid flow, the chambers include an inlet chamber, a preliminary chamber, an outlet chamber, a discharge chamber, and a reservoir chamber. A first orifice on one inner wall permits passage of fluid from the inlet chamber to the preliminary chamber, a second orifice on another inner wall permits passage of fluid from the preliminary chamber to the outlet chamber, and a third orifice on another inner wall permits passage of fluid from the outlet chamber to the discharge chamber. The relief member has a cap and is coupled to the reservoir chamber. The inner walls defining the chambers are of a height approximately between 70 Length % to 95 Length % of the height of the outer walls of the device to permit for a waste accumulation layer.