If ST108 Is Voluntary, Why Is It Costing Surgery Centers Real Money?

ST108 is voluntary in the way a suggested speed is voluntary when a patrol car is behind you. No federal or state rule orders a surgery center to follow ANSI/AAMI ST108, the national standard for the water used to process medical devices. But Medicare’s conditions for coverage require every ambulatory surgery center to document that it has selected and implemented nationally recognized infection control guidelines, and for processing water, ST108 is the nationally recognized guideline. A center that treats it as optional usually finds out otherwise at survey time.

The Ambulatory Surgery Center of Niagara learned the price of that distinction firsthand. Becker’s ASC reports that the small, privately owned center in Niagara Falls, New York, had rinsed instruments with distilled water for years. To meet ST108, it installed a reverse osmosis system with ultraviolet treatment and endotoxin filtration, and the new system carries ongoing testing obligations with it. The center’s administrator, Kimberly Fullone, told Becker’s that the rules help keep patient care strong, “but it comes with a high price tag to keep up with all of these new requirements.”

What ST108 requires

ST108’s full name is ANSI/AAMI ST108:2023, Water for the processing of medical devices, published in 2023 by the Association for the Advancement of Medical Instrumentation. It is the first edition of an American National Standard on the subject, and it replaced AAMI TIR34, a technical report that offered guidance without a standard’s weight. The upgrade from report to standard matters: guidance can be weighed, while a standard is what surveyors, accreditors, and equipment manufacturers measure against.

The standard sorts processing water into categories matched to risk. Utility water is the workhorse grade, used for flushing, washing, and intermediate rinsing. Critical water is the extensively treated grade, produced with steps such as reverse osmosis or deionization and used where the water last touches the device: the final rinse after high-level disinfection and the final rinse of critical devices before sterilization. Steam is the third category, covering the water vapor that sterilizers turn into the sterilizing agent itself.

Each category carries quality limits and a testing rhythm. Critical water is monitored monthly, with conductivity checked far more often, while utility water and steam are tested quarterly, according to laboratory summaries of the standard. The tests cover bacteria and bacterial endotoxin counts, total organic carbon, hardness, conductivity, pH, and ionic contaminants such as aluminum, copper, and zinc. Some of that can be measured at the sink; the microbiology and chemistry go to a lab.

ST108 also assigns the work to people, not just equipment. The standard calls for a multidisciplinary team responsible for water quality, a risk analysis, validation testing when a treatment system is installed or qualified, and records showing the monitoring actually happened. A center can buy the right hardware and still fall short if nobody owns the program and the testing log is thin.

Why “voluntary” is a trap

The enforcement mechanism is indirect, and that is exactly why it catches administrators off guard. The regulation a CMS surveyor cites is 42 CFR 416.51, the infection control condition for coverage for ASCs. Section 416.51(a) requires a sanitary environment maintained by adhering to professionally acceptable standards of practice. Section 416.51(b) requires an infection control program that includes documentation the center has “considered, selected, and implemented nationally recognized infection control guidelines.” ST108 is never named in the regulation; it enters as the yardstick the surveyor uses to judge whether those sentences are true.

Accreditation runs on the same logic. Becker’s reports that The Joint Commission, in alignment with CMS, uses ST108 as a benchmark during accreditation surveys. Ray Schwalbe, a mechanical engineer at HGA, put the result plainly in a January article for PHCPPros: meeting ST108 makes it “a de facto enforceable standard even though it is not explicitly mandated.” A center does not get cited for violating ST108. It gets cited for an infection control program that cannot show it follows the recognized standard for the water touching its instruments.

The exposure is not theoretical, because infection control is already where ASCs get cited most. Becker’s reports that of 3,023 ASC surveys in 2023, the most frequently cited health deficiency was sanitary environment (507 citations) and infection control program requirements ranked second (372), per CMS data reported by the Ambulatory Surgery Center Association. Water quality sits inside both categories, so a weak processing-water program is exposed on the two most-traveled survey paths at once.

What compliance looks like for a small ASC

Small centers feel the cost differently than hospitals do, and the difference is purchasing power, not effort. Fullone told Becker’s that health systems buy in larger quantities and negotiate better pricing, while a single-site center pays closer to list for the same RO skid, filters, and lab testing. The standard makes no allowance for facility size: the endotoxin limit on a final rinse is the same in a two-room ASC as in a flagship hospital.

For a small ASC, compliance in practice looks like four things. First, treated water at the points the standard names, typically an RO-based system with disinfection and endotoxin control for critical water. Second, a lab relationship that produces results on the standard’s schedule, not when someone remembers. Third, a named owner for water quality, even if the “multidisciplinary team” is three people with other jobs. Fourth, documentation a surveyor can follow: the risk analysis, the installation validation records, and the monitoring log.

The time to build that file is before the survey window, not during it. Fullone’s advice to other small centers, as Becker’s reports it, starts with the budget: “Plan on it. Know that there’s going to be things that are going to come up.” She also described getting multiple vendor quotes on major purchases and asking peer centers which companies they used and what they paid.

The plain answer to the headline question is that “voluntary” describes how ST108 was written, not how it is used. AAMI wrote it as a consensus standard. CMS wrote a regulation that points at nationally recognized guidelines. Surveyors and accreditors connect the two, and the connection is where the money goes.