Pre-use post-sterilization integrity testing (PUPSIT) verifies the integrity of an installed and sterilized sterilizing-grade filter assembly after sterilization and before product filtration. Unlike pre-sterilization and post-use integrity testing, PUPSIT addresses the verification gap between sterilization and product use. This study identified and prioritized risks associated with retrofitting PUPSIT into existing hard-piped sterile filtration systems and proposed practical management strategies. Regulatory requirements and technical guidance were reviewed, and pre- and post-retrofit P&IDs, valve configurations, SIP sequences, HMI/control structures, and equipment interfaces of a case-study system were compared. FMEA was performed using severity, occurrence, and detection scores. Eighteen failure modes were evaluated. The highest risk was improper joining, fastening, or sealing of new piping and connections (RPN 80). Exclusion of the installed and sterilized final sterilizing-grade filter from the test boundary, failure of mutually exclusive control among production, SIP, and PUPSIT modes, and initiation of product filtration before confirmation of an acceptable PUPSIT result each had an RPN of 75. Major risks were concentrated at interfaces between new PUPSIT functions and existing piping, SIP, automated controls, and record-management systems. A staged strategy covering design, installation/qualification, and routine operation was proposed.