A backwashable self-cleaning strainer has a vertical housing containing a rotatable strainer basket. The housing has an inlet adjacent the top thereof and an outlet adjacent the bottom wall, with a flush discharge opening in the bottom wall. Components for rotating the strainer basket are located outside the flow of water containing particulates that enters the housing. A hollow backwash conduit with a passage through the sidewall is positioned adjacent the inner surface of the strainer basket and communicates with a sealable aperture in the wall of the housing. Upon opening of the aperture, cleaned water flows through the side wall of the strainer basket, removing particulates therefrom, and out the hollow backwash conduit. An intermittently rotatable brush is also provided to brush the inner surface of the strainer basket.