Distilled water = Water For Injection Sterile Distilled water = Sterile WFI. “Sterile Water for Injection (see the USP monograph) is Water for Injection packaged and rendered sterile. It is used for extemporaneous prescription compounding and as a sterile diluent for parenteral products. It may also be used for other applications where bulk Water for Injection or Purified Water is indicated but access to a validated water system is not practical, or where only a relatively small quantity is needed. Sterile Water for Injection is packaged in single-dose containers not larger than 1 L.” So the way I see it, the difference between those two is that: