The invention is directed to a sprinkler body having a side inlet and improved strength and durability. The side inlet is reinforced with additional structure at a cylindrical wall defining the side inlet. The structure may include a reinforcement rib located within the sprinkler body and intersecting the side inlet. The structure may include a plate located within the cylindrical wall, and the plate may include a collar and/or a crosspiece spanning the side inlet. The structure permits passage of water therethrough and serves to reinforce localized weakened portions or stress concentrators of the side inlet or the sprinkler body.