A dental laboratory installed a washer-disinfector and treated the first failed validation run as a machine fault. The engineer found nothing wrong with the unit. The failure traced back to how the load was arranged and how the detergent was dosed, both of which the team had assumed were the manufacturer's concern. What follows is the sequence the lab worked through, in the order that stops a clinic replacing equipment it does not need to replace.
What is a washer-disinfector validation run actually testing?
A validation run is a test of the whole process as configured on the day, not just of the machine. That process includes the unit, the load, the chemistry, the water, the temperature and time parameters, and the way the load is presented to the spray arms. The ISO 15883 family of standards addresses washer-disinfectors and the test methods used to check them, which is why a failed run is reported against a test method rather than as a machine error code.
The lab's first mistake was reading the failure as a device problem. The second was rerunning the same configuration and hoping for a different result.
What should be checked first when a validation run fails?
| Check | What goes wrong | Why it produces a failure |
|---|---|---|
| Load configuration | Instruments nested, trays tipped, hollow items not draining | Spray cannot reach all surfaces, so cleaning is uneven |
| Detergent dosing | Manual dosing, empty drum, wrong concentration | The chemistry is part of the validated process, not an optional extra |
| Water quality | Hard water, filter overdue, rinse stage short | Residue interferes with the result and with downstream sterilisation |
| Process parameters | Cycle shortened to save time, temperature not reached | The run no longer matches the process that was verified |
| Monitoring consumables | Expired or wrongly stored test devices | The evidence itself is unreliable, so the result cannot be trusted |
How did the lab actually fix it?
They started with the load. The instrument trays had been stacked so that the upper tray shadowed the lower one, and the hinged instruments were closed during the wash. Opening the hinges and using the manufacturer's tray inserts for the specific instrument types fixed the coverage problem. Then they moved detergent dosing from a manual guess to the unit's dosing system, and wrote the dose and the drum change date onto the load record.
The third change was cultural rather than technical. The lab stopped treating the daily check as a formality and gave one person the job of signing the run off before the load moved on. Within a month the quality of the rinse water had also improved, because the filter schedule was being followed.
What should the record contain for this kind of equipment?
Record the cycle selected, the load type, the detergent and dose, the water quality check where the unit requires one, the process parameters the unit reports, and the result of the monitoring device used for that run. Keep installation and periodic test results with the machine's maintenance file, since those are the documents that show the unit was verified rather than merely bought.
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Frequently Asked Questions
What standard covers washer-disinfectors in a clinic?
The ISO 15883 family addresses washer-disinfectors and the test methods used to verify them. It sits alongside the sterilizer standards, and a clinic running both types of equipment should be able to cite the standard it is testing against.
Why does a validation run fail when the machine passes its own self-test?
Because the self-test checks the machine, and the validation run checks the process. Load arrangement, chemistry, water quality and the selected cycle are all part of the process, so a machine in good order can still produce a failed run.
How often should a washer-disinfector be tested?
Follow the manufacturer's schedule and the requirement published by the authority that governs the facility. Periodic tests are usually backed by daily checks that confirm the run reached its parameters before the load is released.
Can a clinic run the washer-disinfector without detergent dosing control?
Manual dosing turns the chemistry into a variable that nobody can verify. If the unit supports automatic dosing, using it, and recording the dose and drum change, is the difference between a process that can be repeated and one that cannot.
CliniEco Medical is a licensed medical device establishment (MDEL #35334).
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