Why do we need to use purified water in autoclaves?

It is really important that only purified water is used in autoclave sterilisers, as opposed to normal tap water. The quality of the water used in autoclaves can have a significant impact on their performance and the effectiveness of the sterilisation process, as well as the lifespan of the machine itself.

Purified water is water that has been mechanically filtered or processed to remove impurities and make it suitable for use.  Distilled water was, formally, the most common form of purified water, but, in recent years, water is more frequently purified by other processes including, reverse osmosis, of which is one of the best forms of water to use in an autoclave.


Types of purified water

  • Reverse Osmosis (RO)– Is used to clean up tap water to make it roughly 90-99% pure.  The majority of contaminants found in tap water such as ions, particles, colloids, bacteria, organics and pyrogens are removed, but not 100%.
  • Distilled Water– Is boiled in a chamber until it turns to steam; it is then condensed back into a sterile container and turns back to water. Distilled water still contains a larger amount of chloramines and other chemicals than RO water.
  • Deionised Water (also known as DI or Demineralised water) – This is water that has had the majority of ions removed – these ions can include minerals such as Calcium, Sodium and Copper. The deionisation process removes these ions using a deionisation system.

It is highly recommended to test the water being used in an autoclavewith a TDS meter before use.  Ideally the deionised water should read below 5ppm for autoclave use and deionised water can vary from 0-150ppm depending on where it is purchased.

Using purified water helps to prevent:

  • Contamination: Using water straight from a mains water supply allows the impurities, minerals, and microorganisms that exist in the water to circulate around the autoclave. This not only leads to scale build up but can also contaminate the items being sterilised.
  • Scale Buildup: Tap water often contains minerals, such as calcium and magnesium, and in larger amounts in what we call “hard water” area. This can result in scale buildup in the autoclave chamber and on internal components. In turn, this build up interferes with the proper functioning of the autoclave, reducing its efficiency and potentially causing damage over a small period of time. Please remember that damage caused by scale build up through the use of untreated water is not covered by our Warranty.
  • Low Autoclave Lifespan: The internal components of an autoclave, including steam generators and valves, can be sensitive to impurities in water. The use of water can help extend the lifespan of these components by reducing the risk of corrosion, scaling, and other forms of damage.

Compliance with Standards

In many industries, especially those related to healthcare, there are standards and guidelines for autoclave use. Using purified water is often recommended or even required to meet these standards and ensure the reliability of sterilisation processes.

Testing your water with our TDS Meter will check the ‘total dissolved solids’, or contaminants within the water being used. If you need to invest in your water purification processes, please give us a call – we have a range of options and would love to help!