We’ve produced a number of helpful and insightful articles covering the various methods of water safety, the importance of being properly equipped to monitor and manage your water.

Regular readers might notice that we have previously mentioned 3 recurring factors across our articles, namely – temperature, biofilm and stagnation. In this article, we’re going to delve a little deeper into these elements and hopefully give you the knowledge to help reduce the potential risks associated with your water.


Let’s start with arguably the most impactful of the 3 factors – temperature – or temperature control to be more specific.

Each type of bacteria will have different optimal temperatures depending on matters like natural environment, strain and available nutrients. Now given that most bacteria are mesophilic and grow best between 30°C – 37°C, with optimum temperature being body temperature or 37°C.

Legionella bacteria is no exception to this and is capable of growing between 20°C – 45°C and of course, has optimal growth at 37°C.

Temperature Control

In order to prevent this causing an issue within your water system, two things are required:

  • The first is to keep all cold water below 20°C and while this won’t eliminate the bacteria, it will cause it to lay dormant and halt its growth.
  • At the opposite end of the scale, 60°C and above will kill off the bacteria.

Now keeping cold water below 20°C shouldn’t be too much of an issue, supplying water at high temperatures does run the risk of scalding and countermeasures may be required to effectively prevent one without affecting the other.

Nutrients Including Biofilm

Various nutrients can be identified within a water system, these include silt, inappropriate plumbing materials, airborne contamination and scale amongst others. One of the most significant nutrients is biofilm.

Biofilm is a collective of one or more types of microorganism that can grow on a multitude of substrates and surfaces.

Biofilms have been found both above and below ground, as well as underwater. Common locations include ponds, pools, riverside rocks, fish tanks, pipework, water storage, plant and animal tissues and even teeth.

The thing all these have in common is a wet surface, biofilms thrive in moisture.

Biofilm begins its life as free-floating microorganisms that find their way onto a surface and begin to grow. This initial colony begins to attach itself to the surface and if left alone, these bonds will strengthen and then the biofilm will require a bit more effort to remove.

Not all organisms are able to attach to a surface and some will actually grab onto the other bacteria and matter, causing the biofilm to expand and combined with the multiplying lifeforms within, this can easily get out of hand if left unchecked.

Once the biofilm grows to a sufficient size, it will start to disperse cells allowing the biofilm to spread and colonise new surfaces, meaning that a single colony within a system could potentially spread throughout the entirety.

Biofilm also causes complications with temperature control, the film actually protects the bacteria within from burning away.



Stagnant water is more of a contributing element for the other two factors because when water is left to stagnate it allows biofilm to easily form and temperatures can fluctuate due to constant external interference.

The upside of this is that stagnant water is actually pretty rare in most buildings, as long as an outlet is used once a week, it will keep the water flowing and prevent any issues.

Stagnation is a more common problem within larger buildings due to the likelihood of stored water. Water cisterns are commonplace within properties that have a high daily demand for water, but the nature of water and supply outweighing demand, results in some water staying in place for extended periods of time.

It’s not just stored water that this can affect, the water within pipework also runs the same risk if not used, effectively meaning that every outlet within a property poses a potential risk.

Avoiding stagnation can be as simple as ensuring to use every tap, shower, etc at least once a week. Be sure to minimise aerosol production as much as possible though, especially if the outlet hasn’t been used in a while.

So there you have it, the terrible trio of factors to avoid when it comes to ensuring safe water.

Got concerns when it comes to water safety? Why not check out our FAQ for common queries within the field or you can contact us for free and impartial advice.