ANSI/AAMI ST108:2023, Water for the processing of medical devices (ST108), changed the way healthcare organizations need to think about water used to process reusable medical devices. The issue is no longer simply whether a purification stage can produce water to target. It is whether the complete water pathway can deliver, maintain and verify the right quality at every relevant point of use.
Water is involved throughout medical device processing, from cleaning and rinsing to disinfection and steam sterilization. Yet for many facilities it has historically been treated as a utility that sits behind the process rather than a controlled part of it.
Published in 2023, ANSI/AAMI ST108:2023, Water for the processing of medical devices (ST108), superseded AAMI Technical Information Report (TIR) 34. AAMI describes ST108 as covering the selection and maintenance of effective water quality, including water treatment equipment, storage and distribution, monitoring, bacterial control and quality-control procedures.
The practical shift is important. Water quality can affect cleaning performance, instrument condition, equipment reliability and steam-related processes. It should therefore be managed as one part of the wider medical device processing system, not as a standalone utility or a one-time water-treatment purchase.
In simple terms, ST108 asks healthcare facilities to understand what water quality each process needs, put the infrastructure and controls in place to deliver it, and continue verifying performance over time.
WHAT DOES ANSI/AAMI ST108 COVER?
Among the AAMI standards for sterile processing, ST108 is the core U.S. standard focused specifically on water for medical device processing. It addresses the quality of water required for different processing stages and the systems and controls needed to maintain that quality. Its scope includes water treatment equipment, storage and distribution, monitoring, testing, maintenance and response to changing operating conditions.
ST108 is an American National Standard developed through a consensus process. It is not, by itself, a federal regulation. That distinction matters, but it should not lead facilities to treat the standard as optional background reading. Its requirements are increasingly relevant to project planning, equipment interfaces, water-quality programs and healthcare procurement.
The standard also does not replace the manufacturer’s instructions for use for medical devices or processing equipment. Water requirements still need to be checked against the specific device, chemistry and equipment being used.
UTILITY WATER, CRITICAL WATER AND STEAM HAVE DIFFERENT ROLES
One of the most useful concepts in ST108 is that not every processing step needs the same water quality. Utility Water is used for many earlier cleaning and rinsing steps, but incoming tap water should not simply be assumed to meet the required parameters. Depending on local water quality, treatment may still be needed.
Critical Water is a higher-purity water category used where tighter control is required, including final-rinse applications. Producing it typically requires a multi-stage treatment process appropriate to the incoming water and the intended duty. ST108 also addresses steam condensate quality, while ANSI/AAMI ST79 remains an important companion standard for steam sterilization.
The practical consequence is straightforward: the goal is not to use the highest-purity water at every stage. It is to deliver the right water quality for each process, in line with the needs of the medical device, processing equipment and applicable manufacturers’ instructions for use (IFUs).
WHY ST108 WATER QUALITY DEPENDS ON MORE THAN THE PURIFICATION SYSTEM
Where reverse osmosis (RO) is used, it may produce water that meets a target specification at its outlet, but that does not establish whether the required quality is maintained at every point of use. RO is one common purification technology, not the only route to achieving the required water quality. Purification technology and the microbial-control strategy are also separate design decisions: depending on the system, sanitization may be thermal or chemical. EndoTherm combines RO purification with automated thermal sanitization and is backed by Envirogen’s performance guarantee. The scope of that guarantee must be confirmed for the agreed system specification; the wider hospital pathway still needs to be assessed.
The complete pathway matters: incoming source water, pretreatment, purification, storage, distribution, recirculation, accessible points of use and sampling locations, monitoring, remote monitoring and data logging where available, bacterial and biofilm control, sanitization, maintenance and verification. A weakness upstream or downstream of the purification equipment can compromise water quality even when the treatment plant itself performs as specified. Remote monitoring can add another layer of operational visibility by giving facilities and service teams access to system performance data and alerts between site visits. Envirogen’s EndoTherm range combines RO purification and automated thermal sanitization with remote monitoring options, but these features still need to be considered as part of the complete, site-specific water system.
That is why an early, site-wide review of the water infrastructure serving medical device processing can be valuable, and sometimes essential, before equipment or pipework is specified. A suitable provider should be able to review the path from incoming water to the relevant points of use, identify what needs checking and agree the scope of any further investigation. Envirogen offers a complimentary ST108 consultation to talk through the facility’s requirements and the appropriate scope of a site review; the extent of any subsequent survey or water testing should be agreed separately. If water treatment is first considered only when a purification package is being procured, decisions around plant space, utilities, distribution, monitoring, accessible sampling points and equipment interfaces may already be constrained.
The Envirogen Problem Solver series provides two short introductions to the EndoTherm proposition and the wider approach to maintaining ST108 performance over the long term:
ST108 IMPLEMENTATION CROSSES HOSPITAL, MEP AND OEM BOUNDARIES
For hospitals, ST108 implementation is inherently cross-functional. Sterile Processing Department (SPD) teams understand the processing workflow and day-to-day operational consequences. Facilities and Engineering teams understand the building services and existing infrastructure. Infection Prevention/Quality, Biomedical Engineering/Healthcare Technology Management (HTM), Supply Chain/Procurement and leadership may also have important roles in risk, equipment condition, funding, capital planning and ongoing governance.
On new-build, refurbishment and major equipment projects, mechanical, electrical and plumbing (MEP) engineers translate process requirements into physical infrastructure: plant space, power, drainage, pipework, recirculation and utility interfaces. Original equipment manufacturers (OEMs) of washer-disinfectors, sterilizers and endoscope reprocessors define the utility conditions their equipment needs. The water-treatment specialist must then design around the incoming water, demand profile and real operating duty.
An experienced healthcare water-treatment provider should be able to work across those boundaries: with the hospital teams that own the process, MEP designers and installers, OEM project teams, external project-management consultancies and the project management office (PMO) overseeing delivery where one is appointed. Envirogen brings water-treatment engineering, system integration and project-delivery experience to those discussions. Coordinating the requirements early reduces the risk of specifying a capable RO package without accounting for the complete installation, the wider distribution system or the operating responsibility after handover.
WHAT SHOULD A HEALTHCARE FACILITY ASSESS FIRST?
Before selecting or replacing equipment, the first task is to understand the existing or proposed water pathway. That means reviewing incoming water quality and available test data; mapping treatment, storage, distribution and points of use; confirming equipment utility requirements and peak demand; and identifying how sampling, monitoring, sanitization, maintenance and contingency will be managed.
The assessment also needs to cover basic physical realities that are easy to overlook: available plant space, equipment footprint, doorway and corridor widths, the route to position the equipment, lifting and handling access, service clearances, practical access to points of use and sampling locations, and whether the proposed location allows straightforward connection into storage, distribution and recirculation loops. These details can materially constrain system selection or force redesign if they are discovered after equipment has already been specified.
For an existing facility, this creates a practical gap assessment between the current arrangement and the performance that ST108 requires. For a new or refurbished SPD, it provides the basis for engineering the system correctly before space, equipment and contractor responsibilities are locked down.
Water sampling and independent water testing can be an early input to that assessment, rather than something arranged only after a new system has been selected. Results from the incoming supply and relevant points of use help establish the starting conditions, identify issues that need investigating and inform the treatment and distribution requirements. Envirogen can coordinate sampling and testing through an independent accredited U.S. water-testing partner, so the evidence can be considered alongside the engineering and site review. The test scope and results should inform the solution, not be used in isolation to prescribe one.
FROM ST108 TO AAMI TIR119: MOVING FROM UNDERSTANDING TO IMPLEMENTATION
The market is now moving beyond basic awareness of the standard. AAMI has been developing AAMI Technical Information Report (TIR) 119, Guidance on Healthcare Implementation and Use of ANSI/AAMI ST108:2023 (TIR119), specifically to help healthcare organizations translate the standard into practical implementation. That direction reinforces the central point: sustainable alignment depends on the whole system and the way it is managed over time.
For hospitals, MEP engineers and OEM project teams, the useful starting question is therefore not simply, “Which RO system meets ST108?” It is: “What does this facility need the complete water system to do, and how will we prove that it continues to do it?”
That is also why proven implementation experience matters. ST108 is not, by itself, a federal regulation, but if water quality, equipment performance or reprocessing controls are challenged, a facility may still need to demonstrate how its approach was assessed, designed, monitored and maintained. Working with an experienced water-treatment provider can bring practical learning to decisions that cross design, installation and lifecycle operation.
Envirogen combines relevant U.S. healthcare project-delivery experience with many years of healthcare water-treatment experience across the UK, Australia and New Zealand, working within established regulatory and technical frameworks. Those requirements should not be treated as identical to ST108; the value lies in applying transferable engineering, decontamination and water-system experience to the specific requirements of U.S. healthcare.
SEE OUR U.S. WATER-TREATMENT CAPABILITY FIRST-HAND IN MEMPHIS
Envirogen’s U.S. presence includes our manufacturing facility in Memphis, where we regularly welcome hospital teams, OEMs, MEP/consulting engineers and other project stakeholders to tour the facility, meet our team and see our water-treatment systems and capabilities first-hand.
Envirogen supports early technical and site conversations to help establish those requirements. Where treatment infrastructure needs to change, EndoTherm healthcare water purification systems can then be engineered around the actual process demand, footprint, resilience, purification, microbial-control strategy, remote monitoring and lifecycle requirements rather than treated as an isolated equipment purchase.
ADDITIONAL READING
- From AAMI TIR34 to ST108: What Changed for Sterile Processing Water?
- Sterile Processing Water Requirements: Designing the Complete ST108 Water Pathway
- Sterile Processing Water Testing: What Hospitals Need to Verify
- Hospital Sterile Processing Water Specification: What Should Be Reviewed on Site Before Selecting a New ST108 Water System?
- Water Quality Issues in Sterile Processing: The Hidden Cost to Instruments, Equipment and Uptime
- Thermal Sanitization vs Chemical Sanitization for Sterile Processing Water Systems
- Maintaining Performance After Commissioning: ST108 Water Monitoring, Testing and Lifecycle Support
GET YOUR FREE ST108 CONSULTATION
Reviewing an existing SPD, planning an upgrade or replacement, or designing a new department?
Request a complimentary ST108 consultation to talk through water quality, space, access, distribution, monitoring and lifecycle requirements before the next approach or specification is fixed.
Want to explore ST108 in more detail?
Download the latest version of the ST108 White Paper for an overview of ANSI/AAMI ST108:2023, the shift from TIR34 and key water-quality considerations for sterile processing, with real-world examples and practical insight into system design, operational risk and long-term performance.