ST108 Testing

ST108 testing refers to a comprehensive water quality testing program based on the ANSI/AAMI ST108 Water Quality Standard. This standard has been developed to monitor and control water used in critical processes, especially in healthcare sterilization and equipment cleaning. The goal of ST108 testing is to ensure that the water used in sensitive applications is chemically balanced, microbiologically safe and free of contaminants that could damage equipment or introduce microorganisms.

What ST108 Testing Measures:

ST108 testing evaluates a wide range of physical, chemical and microbiological parameters to provide a full picture of water quality. Typical testing includes measurements such as pH, conductivity, total alkalinity, total hardness and total organic carbon (TOC), which describes the basic chemical and physical properties of the water. These indicators help determine whether the water is corrosive, mineral-rich or carrying suspended material that could interfere with processes.

The analysis also includes ionic and metal contaminants, such as aluminum, chloride, copper, iron, manganese, nitrate, phosphate, sulfate and zinc. Elevated levels of these compounds can lead to scaling, staining, corrosion or chemical residues on equipment. Monitoring these parameters ensures the water meets strict quality thresholds and does not damage instruments or interfere with detergents and cleaning processes.

Microbiological Testing:

Another critical component of ST108 testing is microbial monitoring. Tests such as heterotrophic plate count (HPC) and endotoxin analysis are used to detect microbial contamination in water systems. These tests help prevent biofilm formation and bacterial growth that could compromise sterilization or contaminate surfaces and devices.

Types of Water Evaluated:

The ST108 framework typically separates water into several categories depending on how it is used:

• Utility Water: incoming or pretreated water used in washing or equipment supply lines.
• Critical Water: highly purified water used in final rinses or sensitive processes.
• Steam Condensate: water generated from steam used in sterilization systems.

Sampling:

Because samples can be easily contaminated during collection, special care must be taken when collecting water samples. Click here for sampling instructions.