Legionella risk with calcified taps – an underestimated danger

Why calcified taps are a problem

When carrying out Legionella risk analyses, we have encountered this very often: calcified tap work resulting in aerosol formation.

Under normal circumstances, standard sink or basin taps pose little risk of Legionella contamination. When functioning correctly, they produce an even water jet with no aerosol formation, or, depending on the type of tap and the water pressure, minimal aerosol formation. But when taps become calcified and dirty, this situation changes. The limescale deposits cause a partially clogged aerator (the "filter," as we call it), which in turn disrupts the water jet and causes the water to atomize into fine droplets (aerosols). This is clearly illustrated in the photos below, which we took in a kindergarten:

When the water is contaminated with Legionella bacteria, these contaminated aerosols can be inhaled. This creates the risk of Legionnaires' disease (severe pneumonia) or the milder variant, Pontiac fever. If such taps reduce user-friendliness, a different tap may be preferred, resulting in less frequent use of the calcified tap. Limescale also serves as a breeding ground and a source of bacteria.

In short: multiple risk factors that result in a legionella risk.

Additional risk in nursery schools, but also daycare centres

The danger of such calcification is especially great in young children:

• Eye level with the tap: Children often stand at the same height as the tap. This makes them more likely to inhale the aerosols directly;

• Vulnerable group: Young children have a more sensitive immune system;

• Holiday periods: If a stagnation lasts longer than a week, the risk of Legionella growth increases exponentially. This is especially important to pay attention to after the summer. The water has been stagnant for a very long time and often reaches a risky temperature in summer temperatures.

Lime: a breeding ground for bacteria

As briefly mentioned, limescale deposits aren't just a technical problem. Bacteria thrive on limescale in pipes for several reasons:

• Adhesion: Lime provides a rough surface where biofilm can easily adhere. To put it simplistically, bacteria need a rough surface to establish themselves;

• Reduced flow: A clogged tap is used less often and flows less vigorously, meaning water sits stagnant for longer – precisely the conditions in which Legionella can multiply.

  
  

Maintenance: a simple and effective measure

Fortunately, this risk can be easily prevented and reduced. To limit the risk, we recommend at least the following:

• Check just before the new school year, as the summer break increases the risk of legionella, it is advisable to carry out a check and determine whether such problems occur, and at which taps;

• Descale and clean all taps annually , especially in (nursery) schools and daycare centres.

• Restoring an even water jet to minimize aerosol formation. If this isn't possible by descaling or cleaning the tap, ideally, replace it.

  
  

Call to action

We strongly recommend that schools, daycare centers, and their maintenance services check and clean their taps as needed before the start of each school year. This reduces the risk of Legionella contamination and protects both children and staff.