AAMI ST108 Microbiological Quality Sampling Procedures

The ST108 sampling information below is provided as a summary for reference and are not exhaustive. You are advised to contact Legionella Control Systems for more comprehensive and detailed sampling procedures related to the AAMI ST108 standard. Learn more about ST108 testing and ST108 risk assessments.

Also see ST108 Sample Collection Types and Procedure Overview for additional information on ST108 sample containers for the types of test.

General Sample Collection Notes for ST108

  • AAMI ST108 water samples from multiple distribution system locations for representative water quality.
  • Sample at the beginning and end of the water distribution loop.
  • Include point-of-use locations where water enters equipment for medical device processing.
  • Sample after the purification process and at the exit of storage tanks.
  • Always collect samples before disinfection of the water treatment system.
  • For new systems, collect and test water weekly until a pattern is established.
  • For established systems, collect and test water monthly or as indicated by historical data.

ST108 Sampling Consistency

  • Maintain consistent sampling procedures and locations to ensure accurate water quality monitoring

ST108 Sampling Containers

  • Use appropriate sampling containers to avoid introducing contamination into the test sample.
  • Containers should meet required quality standards (e.g., pyrogen-free for endotoxin sampling).


  • Adjust flushing duration according to water system and distribution loop size.
  • Standardized flushing before sampling can disrupt biofilm growth and minimize microbial contribution from sampling points.
  • Ensure that sampling locations are not stagnant when not in use and are accessible for distribution loop disinfection.

ST108 Sampling Technique

  • Ensure that valves, taps, and hoses used for sampling are designed not to contaminate the sample.
  • Sampling locations should not create stagnant water environments when not in use and should be accessible for disinfection.
  • Disinfect sampling surfaces (e.g., valves, hoses) externally and internally before sampling.
  • Wear gloves when collecting samples.
  • Do not rinse the bottles. The bottles are sterile so care must be taken not to contaminate the bottle or cap.
  • Open sample taps and allow water to run for at least 60 seconds before aseptically collecting samples in sterile, endotoxin-free containers.
  • Once the line is flushed and the flow reduced, quickly open the bottle (but do not set the cap down), hold the cap by its outside edges only, and fill the sample bottle to just above the 100 mL line leaving a 1-inch headspace.
  • Cap the bottle immediately and place it into a cooler with ice for delivery or overnight shipment to the lab.
  • Collect water samples directly from outlet taps in different parts of the distribution system.
  • Collect a minimum of 100 to 300 mL of water for all samples other than Endotoxin samples (15 ml tube).
  • Treat sample taps with an alcohol-based disinfectant before sampling and ensure they are completely dried. Do not use bleach or other disinfectant solutions.
  • Keep samples on ice or at 4°C (39°F) until delivery to the laboratory for testing.
  • Employ aseptic technique during water collection.

Contact Legionella Control Systems at 888-416-8626 for more comprehensive and detailed sampling procedures related to the AAMI ST108 standard.