a method for installing a pipe liner in a pipe includes the steps of reducing the diameter of the liner , so that it can be positioned within the pipe , installing the liner in the pipe , enlarging an upstream end of the liner , disposing a liner expander within the upstream end of the liner , pressurizing the upstream end of the liner with a heated fluid , the temperature of the heated fluid being sufficient to soften the liner , and the pressure of the heated fluid being sufficient to propel the liner expander from the upstream end of the liner to a downstream end , allowing a portion of the heated fluid to bypass the liner expander for heating and softening the liner ahead of the expander , and reducing the temperature of the pressurizing fluid to cool the liner below the softening temperature , to allow it to stiffen and form a liner within the pipe .