What is the Best Piping for Central Sterile Processing and ST108?

Below are some considerations for ideal pipe materials used for sterile processing that will assist with conformance to the AAMI ST108 standard for sterile process water. Choosing the correct piping will minimize biofilm and pathogen growth as well as reduce the potential for an increase in water total dissolved solids (TDS) and conductivity. It is important that you not rely directly on this information because every application is different. Please contact Legionella Control Systems for a detailed ST108 Risk Assessment as well as ST108 testing to determine the best piping for your application. Sterile processing has three main water classifications: Utility, Critical, and Steam (Condensate). The below information is for critical water.

Types of Pipes to Consider for Critical Central Sterile Water and ST108

  • Beta Polypropylene Standard (also called Poly Pro Standard): This pipe has a UV inhibitor included to prevent piping degradation as well as bacterial and biofilm growth.
  • Natural Polypropylene: This is typically used only for bead and crevice-free applications but fluorescent light and UV will degrade this piping, so this should be wrapped with insulation.
  • PVDF Plus: Typically this piping is beyond what is needed for ST108 and sterile processing.
  • PVDF Standard: This is used in the majority of applications where polypropylene is not appropriate, and adds substantial costs.

Types of Pipe Joints to Consider for Critical Central Sterile Water and ST108

  • Socket Fusion: This is the best joining method for the majority of sterile water applications and ST108.
  • Conventional Butt Fusion: This method is not useful for most high-purity water applications due to its bacterial growth potential.
  • Infrared Butt Fusion: Machines control quality so all the joints are exactly the same. This is a higher-quality joint but cannot be used if there is a requirement for 100% draining.
  • Bead and Crevice Free Fusion: When 100% drainage is required, this joining method is required. Typically, this is used for water for injection (WFI), and natural, unpigmented polypropylene piping must be used. Pigmented, standard polypropylene piping cannot be used.

Additional Considerations for Central Sterile and ST108

  • Most applications should have a water velocity of 3-5 fps; above 5 fps, the system may experience hydraulic shock (water hammer). Water velocities below this range increase the probability of biofilm and pathogen growth.
  • Ozone is a stress-cracking agent, which can cause degradation in polypropylene piping systems. If Ozone is going to be used, consider PVDF or stainless steel piping.
  • If heat sanitization is required, PVDF or stainless steel piping should be used.

Note on Piping for Related Water Treatment Systems

PP = Polypropylene | CPVC = Chlorinated Polyvinyl Chloride | PVDF = Polyvinylidene Fluoride

Utility Water*

Softening: Most piping can be used.

Carbon Filtration: Most piping can be used.

Microfiltration: Most piping can be used.

Ultrafiltration: CPVC, PP, PVDF, 304 or 316 stainless steel

Critical Water

Nanofiltration: PP, PVDF, 304 or 316 stainless steel

Reverse Osmosis Filtration: PP, PVDF, 304 or 316 stainless steel

Mixed Bed Deionization: PP, PVDF, 316L stainless steel

Steam Condensate

304 or 316 stainless steel

*Though most piping can be used for the delivery of utility water, CPVC and stainless steel piping are preferred.

There is a very complex area, so for more information on piping, testing, and risk assessments for ST108, central sterile, and other water treatment systems, contact the experts at Legionella Control Systems.