There are several different types of water that are used in pharmaceutical production. In each of these, the TOC of water and bioburden in the water system should be properly monitored. Each is used at different steps in the process and has different specifications for purity. Purified Water (PW) is water that has been processed to remove impurities to low levels. Water for Injection (WFI) is water used as an excipient in the production of parenteral medications. Ultrapure Water (UPW) is water that has been purified to extremely low levels of impurities that must meet very strict specifications.