Purified Water (PW) is the most-used cGMP utility — and one of the most-cited in audit observations. A clear primer on loop design, sanitization strategy, distribution, and validation.
1. Source Water Treatment
Pre-treatment (multimedia filter, softener, carbon, ultrafiltration) → RO → EDI (or double-pass RO) → PW. Every step matters for microbial control and conductivity.
2. Storage & Distribution Loop
- Stainless steel 316L electropolished
- Continuous re-circulation at > 1 m/s velocity
- No dead legs > 6 pipe diameters (USP) or 3D (stricter)
- Sloped piping with sanitary drains
- Orbital-welded joints (documented)
3. Sanitization Strategy
Three common methods:
- Hot water sanitization at 80°C for 60 minutes — most common in India
- Ozonization for ambient loops
- Chemical sanitization as periodic backup
4. Monitoring Parameters
- Conductivity: continuous, USP <645> compliant
- TOC: continuous, USP <643> compliant
- Microbial count: weekly sampling per defined plan
- Endotoxin: as required by product
5. Validation Strategy
3-phase validation:
- Phase 1 (14 days): Intensive sampling, daily testing
- Phase 2 (14 days): Demonstrate consistent control
- Phase 3 (1 year): Long-term performance with seasonal variations
Conclusion
PW system design rewards engineering discipline. Cut corners on velocity, dead legs, or sanitization and the loop will fight you for its entire operating life.
At H&G, we design, qualify, and troubleshoot PW and WFI systems across pharma facilities in India and overseas. Contact us for system design or qualification support.