an apparatus and method for installing casing into a wellbore is provided . the apparatus includes a piston assembly which is engagable with a casing string to be installed into a wellbore . the piston assembly works in conjunction with a previously installed section of casing in the wellbore to create a hydraulic piston system to aid in the installation of the casing string to which the piston assembly is attached into a wellbore . more particularly , the piston assembly in conjunction with an intermediate casing is used to aid in the installation of a casing string comprising production casing . a method of operating the piston assembly is also provided .