Sometimes it seems there are too many options for disinfecting a water system! As well as that, there are plenty of things to consider in making the decision. One thing is very clear – one size does not fit all! What works in one building will fail in another building, or street, or town. This can make it hard to choose the right direction to take. Here are a few quick tips on  making the choice, and some links to posts on technologies you might be considering.

More and more, disinfecting a building water system is becoming a necessity. In some States it is a legal requirement either routinely, or in response to Legionella test results. Depending on the level of risk you are dealing with. There is no doubt that the market for disinfection in health and aged care is growing rapidly. This is in response to legislative change and increasing appreciation of health risks from Legionella and other bacteria in the building water system.

Getting your priorities right

Firstly, if the goal is to control Legionella, disinfection is not the first step. It is probably the last. Good water system design is a good start and the first step. Secondly get the system operating and maintained to make it as difficult for the bacteria as possible. This includes good documentation and a communication plan. Most of us don’t have the luxury of designing the system we operate. So a review of the system and identifying changes that will improve performance and reduce risk is essential. All of these can be part of a Water Risk Management plan. Once these are put to bed it is time to consider disinfection.

Be aware that disinfection is not elimination. No disinfection process will remove (eliminate) Legionella from a system it can only assist in controlling it. If the systems’ design, operation, and maintenance are not up to scratch then disinfection is likely to fail. Getting the system running at its’ best gives the disinfectant the best conditions to work for you.

So, assuming you have the system running smoothly, what do you need to think about when choosing a disinfection plan.


Things to consider

Legal obligations:

There are no absolute requirements for installing a disinfection system in Australian regulations. Disinfecting in response to a Legionella detection or case of disease applies in most States. Compliance with relevant regulations and guidelines is a must and the enHealth Guidelines strongly suggest that disinfecting is a good idea. Considering your duty of care is a useful first step in working out things like allocating resources.

Water Chemistry:

Few of us enjoy chemistry but it is a critical thing to consider in making your choice. You are at the mercy of your water supply. It can be modified to suit the disinfection – but that means $$$. There are no disinfection processes that do not need the right water chemistry to work properly. Just a bit of time looking at the supply water quality can narrow the list of options for disinfecting your system.

Water Use:

Checking out how the water is used and by who is going to tell you what your target for disinfection will be. Some sites may require much more attention and effort than others. What volume of water will you be using? How many outlets do you have? What sort of outlets? Who will use them?


For the treatment to work it must ‘fit’ the system in practical terms. Do you have the space? What technical knowledge do you need? Have you got the human resources? Paying for a system you can’t operate is throwing money away!


Disinfecting any system is possible. But it may drive you into bankruptcy in the process. Work out the cost of the treatment and balance it against your water chemistry, use and resources. Check out the costs for installation, chemicals and maintenance.

Making the Call

Once you have made a checklist of the above considerations then the process of selecting a disinfectant strategy gets easier.  Below are list of the most common disinfection treatments currently available for drinking water systems. To drill down on these just click the link and it’ll take you to a more technical review of the treatment with background reading if you’re keen.

Physical processes

These are methods of disinfecting that don’t use chemical addition to the water.

  • Filtration – usually used with other treatments to remove debris from the water and improve disinfection. More recently used at outlets for ‘point of use’ sterilisation of the water.


  • Ultra-violet radiation – common in warm water and rain water systems where water is recirculated through a UV lamp to disinfect it. Also used at outlets for ‘point of use’ disinfection for clinical services (hand washing).


  • Temperature – keeping water outside the growth range of Legionella is a good idea – and a design consideration. Sometimes this is impossible, but it can be used for disinfection (pasteurisation).

Disinfecting with chemicals

These are methods of disinfecting that use chemical addition to the water.

  • Chlorine – the most commonly used and probably oldest means of disinfecting drinking water.


  • Chlorine dioxide – a newer technology in drinking water, with a long history in industrial systems.


  • Copper / Silver Ionisation – a newer technology for drinking water treatment. Copper and Silver ions are introduced into the water electrochemically on site.


  • Monochloramine – widely used in water utilities in Australia, but can be adapted for smaller building water systems.


Finding out what will work for you will take a bit of research. Asking yourself a few questions about what you are trying to achieve is a good start. There is no product on any market that is guaranteed to work in your building without a good hard look at what your system and supply water looks like. Cost, maintenance and resources are as critical in achieving success as the properties of the disinfectant you choose.

Further Reading

Australian Drinking Water Quality Guidelines 6 2011 Version 3.3 Updated November 2016.

EnHealth (2015) Guidelines for Legionella Control.

World Health Organisation (2007) Legionella and Prevention of Legionellosis