Water in Medical Device Manufacturing: Types, Uses & Standards
Water is more than just H₂O in the medical device world. It’s a critical raw material used in cleaning, manufacturing, and even as a device component. Whether you’re sterilizing surgical instruments or preparing implantable devices, water quality can make—or break—compliance and patient safety.
In this post, we break down the types of water used in medical device processing, inspired by standards like ANSI/AAMI ST108, USP, EP, and more.
Where Is Water Used?
Types of Water in Medical Device Processing
- 🚰 Utility Water (Potable Water)
Basic water used in facility operations. Not for final rinsing or critical use.
Key Specs:
- pH: 6.5–8.5
- TDS: < 500 mg/L
- Microbial Quality: No coliforms
Standards: WHO, IS10500, EU DIRECTIVE 98/83/EC
Applications:
- General facility use
- Feed water for purification systems
2.💧Purified Water (PW)
Treated water with low organic and ionic content.
Key Specs:
| USP Limit | EP Limit | |
| TOC: | < 500 ppb | < 500 µg/L |
| Conductivity: | < 1.3µS/cm@25°C | < 1.1 µS/cm @20°C |
| Microbial Load: | ≤ 100 CFU/mL | ≤ 100 CFU/mL |
Applications:
- Rinsing sensitive devices
- Feed water for higher-grade purification
3. ⚗️ Deionized Water (DI)
Ion-free water for mineral-sensitive applications.
Key Specs:
- Resistivity: > 1 MΩ·cm
- TOC: < 500 ppb
- Conductivity: < 1.0 µS/cm
Standards: ASTM D1193
Applications:
- Final rinse stages
- Production of ultrapure water
4. 🔄 Reverse Osmosis Water (RO)
Filtered through semi-permeable membranes.
Key Specs:
- TDS rejection: 95–99%
- Conductivity: 5–20 µS/cm
- Bacterial Reduction: >99%
5. ♨️Distilled Water
Produced via boiling and condensing.
Key Specs:
- Conductivity: < 1.0 µS/cm
- Free from: Most microorganisms & minerals
Applications:
- Final rinsing before sterilization
- Cleanroom preparation
- Sterile solution preparation
6. 🌐 Ultra-Pure Water (UPW)
Treated water with low organic and ionic content.
Key Specs:
- Resistivity: 18 MΩ·cm
- TOC: < 10 ppb
- Endotoxins: < 0.03 EU/mL
Standards: ISO 15883 & ANSI/AAMI ST108
Applications:
- Cleaning of implantables
- Microelectronic medical devices
- Analytical & aseptic assembly
💡 Often produced via multi-step systems: RO → DI → UV → UF
7. 💉 Water for Injection (WFI)
Water of injectable-grade purity.
Key Specs:
- Conductivity: < 1.3 µS/cm
- Bacterial Count: < 10 CFU/100mL
- Endotoxins: < 0.25 EU/mL
Standards: USP, EP
Applications:
- Final rinse for implantable/sterile devices
- Drug delivery device manufacturing
Conclusion
Selecting the right water type is a critical quality decision. From ensuring biocompatibility to meeting regulatory expectations, water treatment and monitoring should align with process needs and global standards.
📘ANSI/AAMI ST108 offers a robust framework for water quality management in medical device processing.
