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Features / July 7, 2023

Washer disinfector considerations

by Jane Renehan

Jane Renehan on considerations before buying a washer disinfector

Jane Renehan answers another question from a reader – this time, on purchasing a washer disinfector.

The question – Dear Jane…

Can you give me some advice as to what I should look out for when buying a new washer disinfector? This will be the first washer disinfector installed into the practice and I would appreciate some basic guidance from you.

The answer

Dental washer disinfectors, sometimes referred to as thermal washers, are currently not mandated in Ireland. 

The Dental Council’s revised Code of Practice Relating to Infection Prevention and Control advises that all new dental premises opened after 1 January 2016 (whether in new or pre-existing buildings) must at least be fitted out to provide for a washer disinfector. 

From my 20 years of experience working with washer disinfectors, I am a strong supporter of their inclusion in decontamination rooms. However, I also know that a washer disinfector has some drawbacks, especially for a smaller practice (see below).

Here are my top tips for anyone considering the purchase of a washer disinfector.

Action plan

When certain criteria are achieved, the washer disinfector increases the quality, safety and efficiency of instrument decontamination processes in a busy practice. 

However, when it comes to washer disinfectors, one size does not fit all. 

So, the first thing you need when considering the purchase of a washer disinfector is your own practice-specific plan to ensure that your ultimate purchase meets the below 11 criteria. 

1. Location

Identify where you will install the washer disinfector. 

Its location should fit naturally into the decontamination process flow, which should always operate in one direction, moving from dirty to clean. For example, you should not install a washer disinfector in the clean zone.

2. Capacity

Before finalising your location, ask yourself if you know what size washer disinfector would best serve your needs. 

Too small and it causes a bottleneck in your decontamination process, which can tie up the dental nurses and require you to hold a larger stock of instruments and handpieces. 

Too large a unit and you either run it partially full, which is inefficient, or you wait until you have sufficient contaminated instruments for a cycle. So, both too small and too large can be problematic.

3. Space

Confirm you have sufficient over or under counter space for your new washer disinfector. 

Most importantly, check there is sufficient depth and width to permit dissipation of heat; also consider that you require adequate room for maintenance. Enquire whether the dose modules require additional space or if they are built into the unit.

Be conscious that, when fully open, the washer disinfector door intrudes horizontally into the room. In narrow rooms, this may be a potential trip/fall workplace hazard.

4. Ventilation 

Be mindful of moisture and temperature control in the room. 

Washer disinfectors can introduce a lot of moisture and heat. Residual moisture (usually below 70oC) may escape when the washer disinfector door is open at the end of the cycle. 

This has the potential to trigger a fire sensor, if located directly overhead.

5. Electrical supply 

Consider the utilities required to support the washer disinfector. 

Washer disinfectors are available in both single and three-phase. Discuss with your supplier which would be best for you prior to making the purchase. 

Ensure that your electrical connection and power circuit can support the safe operation of the unit. 

Electrical sockets located directly behind the unit are difficult to access. My preference is hard-wiring washer disinfectors and having control with an isolation switch, which should be labelled and turned to the off position at the end of the day.

6. Water input and wastewater

Ask what the minimum inlet water pressure is required to efficiently operate the unit. 

If your practice is metered for water usage, it’s worth checking the minimum consumption of water that will be used on a full load. Machines can differ significantly from model to model. 

If you are in a hard water area, you may require a standalone water softener to prevent limescale build-up in your unit. 

Some washer disinfectors recommend using reverse osmosis water in some or all the rinse cycles. If possible, I suggest you try to avoid this, as it just becomes an additional installation and running expense. 

A common point of failure in the installation of washer disinfectors is the wastewater outlet. Wastewater at a temperature of about 93oC is normal, so you require a length of thermal-proof plumbing with appropriately sealed joints. 

This will avoid water leaks or flooding, as the very hot wastewater can melt standard plastic plumbing in just a few months.

7. Data recording and compliance

Always purchase from a reputable dental supplier. Washer disinfectors are manufactured to EN 15883 specifications. This ensures that medical devices (dental instruments) are disinfected correctly and without being damaged. A washer disinfector is not a dishwasher. 

The washer disinfector identification plate contains specified items of information, most importantly the CE-mark accompanied by the European registration number. 

Using a washer disinfector allows for a verifiable and validated disinfection process. Cycle information can be recorded by means of a printer, data logger or networked. Decide which data recording system is best for you now and in the future. 

The washer disinfector requires some daily visual checks and weekly efficacy tests. These periodic tests – together with servicing and maintenance tests – must be recorded and kept for eight years.

8. Installation and running costs

Installation and initial set-up must comply with the Dental Council Code of Practice relating to Infection Prevention and Control. 

Section states: ‘Washer disinfectors must be commissioned and periodically validated by a competent person. “Validation” is the process by which a washer disinfector is tested and verified. 

‘Each act of validation by a competent person should be recorded so that evidence of consistent performance can be provided. 

‘The washer disinfector must be validated annually or at the intervals recommended by the manufacturer’.

9. Internal components

Your new washer disinfector may come with some basic baskets, trays, adaptors and holders but usually, these are bought separately. 

I recommend initially purchasing just what will get you started, as expensive errors can be made at this stage. Where internal components are concerned, no two practices are the same. 

For example, an orthodontic practice will differ significantly from an oral surgery practice. If you use cassettes rather than autoclave pouches, you require a completely different range of internal accessories. 

What volume of handpieces will you be reprocessing in each cycle? Pay attention to the fitting mechanism for cleaning the lumen of your handpieces. Look at the number of adaptors and their filter type. Choose the best options suited to your current and planned future needs.

10. User training

Training should be provided by your supplier at the time of installation. Efficient day-to-day operation and perfect cleaning results are based on a thorough understanding of the unit. 

The practice decontamination lead should draw up step-by-step operating instructions for the users. The manufacturer’s operating manual should be available so that users can check operating information, such as managing error messages. 

11. Research

It always pays to do your own technical background reading in advance of your purchase. Be aware of the total purchase price, installation costs and projected annual running costs before making your decision. 

Compare the technical specifications of your preferred units under the headings of energy use, sound emission and functionality.


In conclusion, start by first knowing your procurement plan. Identify your practice-specific needs before you go shopping. 

Don’t forget my usual advice to consult at an early stage with your dental nurses – they are the ultimate users of the washer disinfector. It can save time and money to include them in your purchase decision. 

Finally, although I’m a firm supporter of washer disinfectors, I fully understand there are circumstances where the traditional cleaning and disinfection methods may be the better option for you. 

On the plus side

  • Fully automated, standardised and verifiable decontamination process
  • Increased quality of instrument cleaning and disinfection
  • Reduction in serious sharps injuries risk
  • Decrease in staff time at instrument cleaning stage, as it eliminates need for ultrasonic baths and manual washing 
  • Speedy management of large quantities, and variety of solid and hinged instruments
  • Instruments and pre-packed cassettes are cleaned, disinfected, dried and ready in one step for sterilisation
  • Effective disinfection of the entire length of a handpiece lumen (hollow A) and other hollow body instruments
  • Scaler tips can be disinfected, unlike with ultrasonic baths
  • Variety of designs available to suit your practice usage such as benchtop, freestanding or built in.

On the minus side

  • Initial investment in appliance, accessories and consumables is a significant expense
  • Running costs – installation/commissioning, consumables, testing, servicing/validation
  • Documentary evidence of functional testing must be held for eight years
  • Additional handpieces and hand instruments may be required
  • Installation considerations – electric (standard single or three-phase), plumbing, data points, printers/loggers
  • Inlet water quality and pressure
  • Inappropriate wastewater outlet plumbing can lead to leaks and flooding
  • Extensive knowledge of manufacturer’s instructions, as ongoing maintenance and changing/cleaning of filters is essential
  • Thorough user induction and refresher training is recommended, as efficiency is operator dependent.

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