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  • Lisamarie Lamb

Hard Water And Legionella

With so many risk variables to consider when assessing the health of a water system and the potential of legionella development inside it, activities such as water temperature and biocide dosage are often prioritised in a risk assessment strategy.

Other characteristics, such as the chemistry of the water itself, are sometimes ignored as less relevant. However, ignoring this fundamental component of the system is a significant error since dangerous bacteria, notably legionella, have been proven to grow more as a consequence of the nutritional advantages provided by the impacts of water chemistry on a system.

Hard water is simply one of several aspects that should be addressed in the context of water management.

What's Wrong With A Little Hard Water?

Hard water, with its richness of minerals, is typically preferred by many people owing to purported health advantages for bones and the heart, for example. However, although there may be some health advantages to drinking hard water, it is not always healthy to your water system and, as a result, may be indirectly generating serious health issues!

If you've ever peered inside your kettle or shower head in a "hard water" region, you've seen limescale - the rock-like white deposits of magnesium or chloride that develop and pile up over time. In hard water locations, pipes, tanks, and appliances inside a water system may get blocked with this same scale if not handled on a regular basis with an efficient de-scaler, just like your kettle or shower head.

The scale can be problematic to a water system by reducing the flow of water and the efficiency of heating/cooling systems, but if you have ever looked closely at that limescale build-up, you may have noticed that it creates a rough uneven surface with lots of tiny cracks and holes in it – basically, a perfect location for bacteria to cling to and the ideal scenario for biofilm to form upon over time.

Biofilms provide an accessible supply of nutrients for bacteria such as Legionella (as explained in a previous post), and by providing them with a perfect surface to grow on, the danger of an infected system rises dramatically with the amount of scale present.

The More Biofilm, The Bigger The Problem

While the presence of a little limescale in a domestic setting may not be too problematic or difficult to deal with, when extrapolated into the water supply for a hospital, care home, or other frequently visited location such as hospitality venues, the associated risk of bacteria and biofilm build-up and subsequent risk posed to human health can increase exponentially.

As a consequence, while performing legionella risk assessments, it is critical not to overlook the chemical make-up of the water, as it may have a substantial influence on the likelihood of potentially dangerous levels of legionella being present inside the system.

Regular de-scaling or softening of the water supply should be explored, and swabbing for biofilm formation should be performed on these systems with a hard water source on a regular basis to check for a concealed supply of legionella pneumophila sg1.

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