With the release of the AS/NZS 4187:2014 standard, Australian day surgeries and hospitals will be required to comply with a range of new requirements for processing reusable medical devices (RMD’s) by December 2021. A particular point of interest is Section 7.2.3 and Table 7.2 – Water Quality Used for Processing RMDs. This section states that water supplied to the reprocessing facility, such as a Central Sterile Supply Department, shall be of a suitable quality for its intended purpose1.

Essentially, to achieve the water quality specified in Table 7.2 the local water supply needs to be treated through a water purification system. Reverse osmosis filters are extremely efficient and effective for the removal of microorganisms and most residual chemicals from water2. In addition to variables such as cost effectiveness, ease of installation, functionality, and footprint, reverse osmosis is by far the most ideal water purification method.

However, what factors does a health facility need to consider before making a decision on the best way to comply with these requirements?

Pipeline and Ring Main

First and foremost it is important for each facility to consider if they’re current pipeline is compatible with a reverse osmosis (R.O) system.  Generally, metal piping should be avoided for use with high purity water3 as R.O water is typically aggressive, and the zinc component in brass is easily lost to the water4.

While there are benefits to a stainless steel ring main such as its longevity; installation and material cost is high. Furthermore, stainless steel has a rough surface finish with crevices that can result in bacterial attachment and early biofilm formation5. A suitable ring main alternative to both brass and stainless steel is un-plasticized polyvinyl chloride (UPVC). Characteristically UPVC has an ultra-smooth internal finish with glued joints which is smoother than traditional stainless steel. Additionally, UPVC is substantially less expensive compared to metal in regards to both manufacture and installation. 

Image 1 - Bacteria in cracks or brush marks on a stainless steel surface following a routine sanitisation5


Storage and pumps


Another important factor to consider is suitable storage of the R.O water to maintain water quality. A pressure tank is a commonly used water storage system which employs a water bladder to control the tank water level. The biggest weakness with this type of system is that ultimately the water sits inside the tank with no circulation. A certain amount of air pressure is also needed to ensure the pump does not start to short cycle.

Ideally, a storage tank integrated with recirculation pumps would prevent a biofilm from developing. Some new tanks can also be equipped with a high and low level water sensor and a secondary over-flow prevention device. These features can prevent the pump from running dry or tank overflow in the event of a sensor failure.

Water Hardness

Dependent on your facilities location, you may also require a water softener which will remove minerals such as calcium, magnesium and iron ions from your local water before the R.O process. Hard water can cause scale during the filtration process, making it extremely difficult for the R.O’s membrane to function and as a result it lowers the quality of the water6. Your local water provider will be able to supply you with information on your local water supply, or alternatively your R.O system supplier will carry out research that will reveal if you require a water softener.

Below is some general information on water hardness in Australia:


  • The typical hardness level of water delivered in Melbourne’s South East area is between 12 – 45 mg/L. This means that the water being supplied to South East Water customers is considered "soft" by international standards7
  • Greater Sydney area water is considered ‘slightly hard’9
  • The water hardness in Perth and the rest of Western Australia is considered ‘hard’, particularly in  country areas10
  • South East Queensland water is considered ‘hard’ to ‘moderately hard’8


Filters and Disinfection

One of the most important features of a quality R.O system is an endotoxin filter. Most new R.O systems are designed with an endotoxin filter which filters out bacterial endotoxins. In addition to an endotoxin filter, an ultraviolet (UV) disinfection system will also prevent a microbial population from developing. When UV light enters a microorganism the energy damages the microorganism’s cellular function rendering it inactive and averting reproduction11.

Image 2 – U.V light inactivation of microorganisms

Traditional chemical disinfection methods require multiple flush cycles to remove residual chemicals. By combining U.V disinfection and an ultra-smooth pipeline, ring main sanitisations are only required every 12 months (carried out by your service provider). The end result being a simplified Reverse Osmosis system with fewer points of failure and lower operating and service costs.

In summary, there is little doubt that an R.O system is the most efficient and cost effective method of meeting the water requirements of AS/NZS 4187:2014. The key is finding the most practical innovations in R.O available at this time.

“Its important facilities take advantage of the new reverse osmosis technology that is now available” Kurt Hogan explains.

The National Product Manager of Mediquip in Brisbane says that the developments in U.V disinfection and research on UPVC as a suitable alternative to metal ring mains, means that facilities have better options than ever before.

“In the last two years Mediquip have had to bust a few long-standing myths on R.O. We’ve done the research and we simply encourage facilities to do the same.”


  1. Water Quality [Internet]. NSW Government Health, 2014 [cited 9 May 2018]. Surface Water Treatment Fact Sheet. Available: http://www.health.nsw.gov.au/environment/water/Documents/Surface-water-Treatment-Fact-Sheet.pdf
  2. Australian/New Zealand Standard
    Reprocessing of reusable medical devices in health service organisations: Fourth ed. SAI Global Limited, p. 54-55 (2014).
  3. CorrosionPedia [Internet]. Corrosionpedia Inc., 2018 [cited 9 May 2018]. Reverse Osmosis Corrosion. Available: https://www.corrosionpedia.com/definition/984/reverse-osmosis-corrosion-ro-corrosion
  4. Geochem Water [Internet].  University of Cincinnati, 2008 [cited 9 May 2018]. Brass Corrosion and Corrosion Scales. Available: http://homepages.uc.edu/~maynarjb/Frontpage%20sites/603/GeochemWater/Brass_corrosion.html
  5. Ryu JHKim HFrank JFBeuchat LR. Attachment and biofilm formation on stainless steel.  Center for Food Safety and Department of Food Science and Technology, University of Georgia, Griffin, 2004, USA.
  6. Water Technology Magazine [Internet]. Endeavour Business Media: Jake Mastroianni. January 2012 [cited 14 May 2018]. The effects of hard water on reverse osmosis filtration systems. Available: https://www.watertechonline.com/the-effects-of-hard-water-on-reverse-osmosis-filtration-systems/
  7. South East Water [Internet]. South East Water Corporation, 2018 [cited 14 May 2018]. Water hardness. Available: http://southeastwater.com.au/LearnAboutWater/WaterQuality/CommonQuestions/Pages/WaterHardness.aspx
  8. Queensland Urban Utilities [Internet]. Central SEQ Distributor-Retailer Authority, 2018 [cited 14 May 2018]. Water hardness. Available: https://www.urbanutilities.com.au/residential/help-and-advice/drinking-water-quality/water-quality-water-hardness
  9. Sydney Water [Internet]. Sydney Water, Government of NSW, 2018 [cited 14 May 2018]. Water Analysis. Available: http://www.sydneywater.com.au/SW/water-the-environment/how-we-manage-sydney-s-water/safe-drinking-water/water-analysis/index.htm
  10. Water Corporation [Internet]. Water Corporation, Government of Western Australia, 2018 [cited 14 May 2018]. Hard water. Available: https://www.watercorporation.com.au/faults/water-quality/hard-water
  11. Public Health [Internet]. Government of Western Australia, Department of Health. 2017 [cited 14 May 2018]. Ultraviolet disinfection of drinking water. Available: https://ww2.health.wa.gov.au/Articles/U_Z/Ultraviolet-disinfection-of-drinking-water