As an old Chinese saying goes, "Water can carry a boat, and it can also capsize it." This rings especially true for steam sterilizer operation in the Central Sterile Supply Department (CSSD). Poor water quality is a hidden threat to sterile processing: it weakens cleaning efficiency, causes instrument corrosion and sediment buildup, breeds stubborn biofilms, and even elevates microbial and endotoxin levels that risk infection spread. What’s more, non-condensable gases (NCG) in water will significantly reduce sterilization effectiveness. Mastering water quality control is therefore the key to safe and reliable autoclave use—let’s uncover the essential water quality rules for your sterilizer.
I. Types of Water Used in Central Sterile Supply Department (CSSD)
Water for cleaning in CSSD includes tap water, hot water, softened water and purified water.
01 Tap Water
It refers to water supplied for daily living and production after purification and disinfection by waterworks, complying with the corresponding national standards. As the basic water for cleaning medical instruments, utensils and supplies, its quality must meet the requirements of GB 5749 Standards for Drinking Water Quality.
02 Softened Water
It is tap water processed by ion exchange resins and other softening methods to remove partial calcium and magnesium ions, containing no or few soluble calcium and magnesium compounds.
Softened water is mainly used for manual or mechanical pre-cleaning and intermediate cleaning steps. When the water temperature is kept below 60℃ during mechanical cleaning, it can effectively prevent scaling on the surface of instruments.
03 Purified Water
It is water from which dissolved cations and anions are removed via ion exchange, reverse osmosis or other suitable processes.
It is mainly used for manual cleaning of precision instruments, final rinsing of all instruments, and thermal disinfection of medical devices, utensils and supplies. According to WS310.1-2016 Administrative Specification for Central Sterile Supply Department in Hospitals, the electrical conductivity of purified water shall be ≤15µS/cm (at 25℃).
04 Distilled Water
It is obtained through a distillation process (condensing steam after boiling), which can effectively remove non-volatile impurities and most microorganisms.
Despite the rapid development of modern water treatment technologies, distilled water remains a reliable high-purity water source in CSSD, and is used for the processing of special instruments requiring an extremely high level of cleanliness.
Ⅱ. Water Quality Requirements for Pressure Steam Sterilizers
Laboratory Sterilizer steam sterilizers require the use of pure water or distilled water to generate steam, preventing minerals in tap water from forming scale inside the sterilizer, which can affect sterilization effectiveness and equipment lifespan. Some precision sterilization equipment even requires the use of purified water to ensure optimal performance. The water quality must meet the requirements of GB 8599 and WS/T 310.1.
III. How to Ensure Qualified Water for CSSD Operations
Perfect the Water Treatment System
01 The Central Sterile Supply Department (CSSD) shall be equipped with professional water treatment equipment (e.g., water softeners, reverse osmosis systems, etc.), which shall be designed and installed in accordance with the water quality grade requirements.
Water Quality Monitoring Requirements
02 Daily monitoring: Test the electrical conductivity, pH value, water color and turbidity before use.
Regular monitoring: Conduct a comprehensive test (including microbial and chemical indicators) at least once a year.
Equipment Maintenance and Storage
03 Water storage tanks shall be made of stainless steel with a sealed design, and be cleaned and disinfected on a regular basis.
For water treatment equipment, consumables such as filter elements, resins, reverse osmosis membranes and activated carbon shall be replaced periodically, and the pipelines shall be inspected regularly.
Standardize Operational Procedures
04 Staff shall strictly use water of different grades in accordance with operating procedures, eliminate incorrect and mixed use of water, and ensure that the water used in each processing step meets the specified requirements.
Ⅳ. Examples of the consequences of improper water use
Scale buildup caused the water level sensor to malfunction, leading to dry heating of the heating element and subsequent damage.
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