Abstract: An adaptor is for a rising disc valve which has a handle for rotating a stem in a housing bore having a shoulder and which displaces a disc valve member which seals against a frusto-conical housing seat spaced from the shoulder. A stack of Belleville -steel springs is between the disc member and the ring seal. An interface ring is between the springs and the ring seal. As the disc member is seated in its valve seat, a ring at the attachment member abuts the shoulder. The attachment member can no longer axially displace and compressively loads the springs as the disc member is further axially displaced to the valve closed state. The compressive load on the ring seal expands the seal radially outwardly against the housing bore and radially inwardly against the piston shank.