A Purified Water (PW) system in pharma is a controlled utility designed to generate, store, and distribute water that meets pharmacopeial requirements for chemical purity and microbiological quality. PW is widely used for non-sterile product manufacturing, equipment cleaning, and as feed for higher grades like Water for Injection (WFI) in some facilities. Because water can easily become contaminated, PW systems are designed to prevent microbial growth, biofilm formation, and recontamination.
Main system elements
1) Feed water & pretreatment
Typically starts with potable water. Pretreatment protects downstream units and includes sand/ multimedia filters, activated carbon (chlorine removal), softener (hardness control), and often cartridge filtration. Chlorine/chloramine control is critical to protect RO membranes.
2) Purification
Most PW systems use Reverse Osmosis (RO) as the core step, often combined with electrodeionization (EDI) or mixed-bed deionizers to achieve low conductivity. Additional polishing may include UV (254 nm) for microbial control and UF for endotoxin reduction where justified.
3) Storage
PW is stored in a sanitary SS 316L tank with sloped bottom, spray ball, and minimal dead legs. The tank is typically protected using a 0.2 μm hydrophobic vent filter to prevent airborne contamination.
4) Distribution loop
A continuous recirculating loop maintains water quality by preventing stagnation. Design features include orbital welds, smooth internal finish, sanitary valves, and properly sized point-of-use outlets. PW loops may be hot (e.g., 70–80°C) or ambient with sanitization (ozone, heat, or chemicals). Continuous circulation and periodic sanitization are key defenses against biofilm.
Control and monitoring
Critical parameters include conductivity/resistivity, TOC, temperature, flow/velocity, pressure, and microbial counts. Routine monitoring uses online instruments plus periodic sampling at worst-case points (end of loop, low-use points, storage tank).
Qualification and validation
PW systems undergo DQ, IQ, OQ, and PQ, with seasonal sampling during PQ and ongoing trending thereafter. A robust PW system supports GMP by delivering consistent water quality, enabling reliable manufacturing and cleaning operations.