Written and maintained by CASRAI Editorial Board
Last updated
General product and use information only, not medical advice. Cycle settings, loading and validation for any real unit come from its manufacturer’s instructions and your facility’s infection prevention policy.
Short answer
A washer disinfector is an automated, closed machine that cleans, disinfects and dries surgical and medical items using water circulation, detergent and heat. The CDC describes these units as generally computer-controlled and compares them to a dishwasher. They are not sterilizers: the CDC lists washer-sterilizers as a separate machine type.
Definition and scope
The CDC’s Guideline for Disinfection and Sterilization in Healthcare Facilities names four common types of mechanical or automatic cleaner: ultrasonic cleaners, washer-decontaminators, washer-disinfectors and washer-sterilizers. It describes washer-disinfectors as “generally computer-controlled units for cleaning, disinfecting, and drying solid and hollow surgical and medical equipment.” The same guideline describes a broader family of automated, closed equipment that cleans and disinfects objects “from bedpans and washbowls to surgical instruments and anesthesia tubes.”
This page covers what the machine does and how its cycle types differ. It does not cover sizing, pricing or brand comparison. For the purchasing side, see sterile processing department equipment purchasing.
How a washer disinfector works in practice
The CDC says washer-decontaminators and washer-disinfectors “act like a dishwasher that uses a combination of water circulation and detergents to remove soil.” Some units add a heat process, and the CDC gives 93 °C for 10 minutes as an example. Cleaning is the first job of the machine. In one study cited by the CDC, a 5-6 log10 reduction was achieved on surfaces that had adequate contact with the water flow in the machine (see log reduction for how that unit of measure works). The condition matters: surfaces the water does not reach are not covered by that result.
The CDC also lists loading points that follow from this. Hinged instruments should be opened fully so detergent solution can reach them, stacking of instruments in washers should be avoided, and instruments should be disassembled as much as possible. Its recommendation (Category IB) is that an automatic washer/disinfector be used in accordance with the manufacturer’s recommendations.
Types and related concepts
Every row below comes from the CDC guideline text.
| Machine or class | What the CDC says |
|---|---|
| Ultrasonic cleaner | Listed as one of the common mechanical or automatic cleaners (see how an ultrasonic cleaner works). |
| Washer-decontaminator / washer-disinfector | Water circulation plus detergent to remove soil; some cycles add a heat process such as 93 °C for 10 minutes. |
| Flushing-disinfector (bedpans, urinals, washbowls) | A short cycle of a few minutes: flushes with warm water to clean, then disinfects by flushing with hot water or steam. |
| Washer-disinfector for surgical instruments and anesthesia equipment | A longer cycle of approximately 20-30 minutes with a detergent, disinfecting by hot water at approximately 90 °C. |
| Washer-sterilizer | Listed as a separate type from washer-disinfectors. |
For respiratory therapy and anesthesia equipment, the CDC’s footnote calls pasteurization in a washer-disinfector “a recognized alternative to high-level disinfection.” For where this fits among disinfection levels, see high-level disinfection and the Spaulding classification.
In the United States, the FDA classifies automated endoscope washers (product code NVE) as class 2 devices under 21 CFR 876.1500 (openFDA, checked 2026-10-30). Endoscopes have their own reprocessing requirements, covered in endoscope reprocessing.
What the temperature numbers do and do not show
The temperatures quoted for these machines come from different sources and answer different questions, so they should not be read as one scale.
- The CDC example of a heat process is 93 °C for 10 minutes, and its instrument cycle disinfects by hot water at approximately 90 °C.
- The CDC notes that strains of Enterococcus faecium can survive the British Standard for heat disinfection of bedpans (80 °C for 1 minute), and calls the significance of this debatable.
- A conference abstract from a Dutch hospital group (van der Velden et al., 2013) states that ISO 15883-3 requires washer-disinfectors to achieve a minimum A0 value of 60 for bedpans, which it equates to approximately 80 °C for 60 seconds or 90 °C for 6 seconds. In its tests, adequate killing of an outbreak vancomycin-resistant enterococcus strain needed an A0 of 180, and an OXA-48 Klebsiella pneumoniae strain needed 120. The authors suggested raising the minimum to at least 180 and noted that a cold start is needed for adequate A0 measurement.
The abstract reports one hospital’s findings and a proposal; it is not a standard. The practical reading is narrow: a disinfection setpoint is a time-and-temperature claim for a specific load, and the cleaning step before it still depends on water reaching the surface.
Where it matters for labs, clinics and supply decisions
The CDC says manual cleaning is used in areas without mechanical units, or for fragile or difficult-to-clean instruments, and that cleaning may be manual or mechanical (Category IB). A washer disinfector therefore does not replace manual cleaning for every item. The CDC’s Category IB recommendation to follow the manufacturer’s recommendations applies to the unit and its loading. See also terminal cleaning for the environmental side of the same program.
Common misunderstandings
- “It sterilizes.” A washer-disinfector disinfects. The CDC lists washer-sterilizers as a different type.
- “A machine cycle guarantees clean instruments.” The CDC’s 5-6 log10 result applied to surfaces with adequate contact with the water flow; hinged items that are closed or stacked can block it.
- “One temperature fits all loads.” Bedpan flushing cycles and instrument cycles differ in length and in what they disinfect, as the table shows.
- “Meeting a standard settles the question.” The bedpan example above shows that a standard’s heat requirement and field findings can diverge, and that the CDC calls the significance debatable.
FAQ
How is a washer disinfector different from an ultrasonic cleaner?
Both are mechanical cleaners in the CDC’s list. The CDC describes washer-disinfectors as using water circulation and detergent, often with a heat or steam disinfection step, and ultrasonic cleaners as a separate type of unit.
What temperature does a washer disinfector use?
It depends on the cycle. The CDC gives 93 °C for 10 minutes as one example, about 90 °C hot water for instrument cycles of roughly 20-30 minutes, and hot water or steam for the short bedpan flushing cycle.
Is a washer disinfector the same as a sterilizer?
No. The CDC treats washer-sterilizers as a separate machine type, and washer-disinfectors as units for cleaning, disinfecting and drying.
Does the manufacturer’s guidance matter?
Yes. The CDC’s Category IB recommendation is to use an automatic washer/disinfector in accordance with the manufacturer’s recommendations.
Sources
- CDC, Guideline for Disinfection and Sterilization in Healthcare Facilities (2008); CDC cleaning page. PDF footer dated June 2024; web page updated November 2023. Checked 2026-10-30.
- van der Velden LB, Nabuurs-Franssen MH, van Leeuwen A, Isken M, Voss A. Thermal disinfection of bedpans: European ISO 15883-3 guideline requirements are insufficient to ensure elimination of ARE and OXA-48 outbreak-strains. Antimicrob Resist Infect Control 2013;2(Suppl 1):O66. doi:10.1186/2047-2994-2-S1-O66 (conference abstract). Checked 2026-10-30.
- FDA openFDA device classification database, product code NVE, 21 CFR 876.1500. Checked 2026-10-30.
