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Can Limescale Buildup Lead to Legionella Outbreak?

Believe it or not, there are different types of water. Now you may or may not know this, hard water could lead to several problems in the house. From destroying your kettle and reducing pressure in pipes to increased energy costs, hard water is not something anyone would want in their home or even in industrial operations.

While there may not be notable physical differences between hard water and soft water, this article tries to investigate the link between limescale buildup and legionnaires disease; asking the question does hard water increases the risk of legionella outbreak both at home and workplace?

Let’s start with the basics first.

What is Hard Water?

Put simply, hard water is defined as water that contains high levels of dissolved minerals, in particular calcium and magnesium.

When rain falls, it seeps into the ground and comes into contact with soil and rock. As the rainwater passes through the soil and rock, it can absorb minerals (like calcium and magnesium) and becomes hard water.

The hardness of the water will vary depending on the local geology.

The table below shows the classifications of hardness in the Republic of Ireland.

Hardness Concentration of calcium carbonate (mg/L)
Soft Water 0 to 75
Medium Hard Water 75 to 150
Hard Water 150 to 300
Very Hard Water Over 300

What is limescale?

Perhaps the biggest problem caused by hard water is the scale buildup associated with it. It’s a white, chalky, but hard substance usually found on and around water spots such as toilet bowls, sinks, taps, bathroom tiles, and inside appliances like washing machines and kettles.

Hard water contains calcium and magnesium carbonate, bicarbonate, chloride and sulphate, all of which are soluble in water.

Limescale forms when soluble calcium bicarbonate decomposes with heat to form insoluble calcium carbonate.

Problems caused by scale buildup in homes

Over time the scale will build up in water pipes, in taps and showerheads, and even in the boiler and radiators. As the scale deposits accumulate, they will reduce flow through the pipes.

Limescale build-up in appliances can reduce their efficiency by a whopping 30%. As a result, appliances would require a lot of energy to heat water because of the insulating limescale layer.

Problems caused by scale buildup in industrial systems

Limescale can cause significant problems in industrial situations. Cooling towers, steam boilers and closed systems can all suffer scale problems.

The build-up of scale in pipes, boilers, cooling systems and other process equipment can cause significant problems to the equipment’s operation and efficiency.

The plant and equipment can fail to work properly, life expectancies can be affected, flow rates can reduce and heat transfer efficiencies can be severely affected.

What is Legionnaires disease?

Legionnaires’ disease is a potentially fatal form of pneumonia. People contract  Legionnaires’ disease by inhaling small droplets of water (aerosols), suspended in the air, containing the legionella bacteria.

These water droplets can then make their way into the lungs via aspiration, which then becomes infected.

Man-made environments can contain the perfect conditions for the Legionella bacterium to multiply and may produce the water droplets that carry the bacterium.

The symptoms of Legionnaires’ disease are similar to the symptoms of flu:

  • High temperature
  • Fever and chills
  • Cough
  • Muscle pains
  • Headaches

In severe cases, there may also be pneumonia and, occasionally, diarrhoea, as well as signs of mental confusion. Some people who have Legionnaires’ disease suffer from nausea, vomiting, diarrhoea and abdominal (tummy) pain.

What is the relationship between limescale & legionella?

Limescale forms due to the minerals in hard water precipitating out and bonding onto surfaces. Especially in areas where water sits for extended periods of time or where water evaporates.

The uneven crusty formation of limescale provides the perfect surface for bacteria to adhere to.

Once limescale has formed, bacteria will attach to the surface and begin to form what is called a biofilm.

Biofilms are collections of one or more species of microorganism including fungi, bacteria and protists. Once some bacteria have colonised the surface their presence makes it easier for more to do the same. Biofilms can be quickly formed if water remains stagnant in the pipes or tanks.

Over time the biofilm grows and harbours bacteria which can cause disease in humans. Some pathogens which are known to grow in biofilms include E.coli, P. aeruginosa, S. marcescens and species of the Genus Legionella which cause legionnaires disease.

The presence of limescale and rust increases the available surface area and contribute to the growth of biofilms.

Limescale is also mineral-rich providing ample nutrients to legionella bacteria.

Does legionella thrive in hard water?

As a living thing, it needs the right conditions to survive and thrive. Many elements influence the risk of legionella bacteria growing in a water supply.

Legionella bacteria thrive in stagnating water in tanks, reservoirs, dead legs in piping systems, and poor-flow areas.

However, the two most important things it needs to proliferate are:

  1. Optimum Temperature
  2. Availability of nutrients

Legionella bacteria thrive in temperatures between 20-45°C, and if water is allowed to sit at these temperatures the bacterium can multiply into large numbers which can cause Legionnaires’ disease.  The bacteria are dormant below 20°C and do not survive above 60°C.

The availability of nutrients is where the presence of hard water becomes a potential legionella issue.

In hard water areas, biofilm can far more readily occur encouraged by the presence of scale inside the pipes which creates the perfect scenario for biofilms to develop over time.

As limescale builds up on the inside surfaces of pipes, tanks and appliances it creates a rough, uneven surface with lots of tiny cracks, holes and fissures which allow biofilms to cling to grow.

These biofilms harbour microbes that Legionella bacteria can use as nutrients and of course, nutrients encourage the bacteria to grow.

How to mitigate the risk of Legionella due to hard water?

Homeowners and people involved in building management must understand the health risks associated with poorly maintained water systems.

Stopping the scale from forming – or at least significantly reducing its presence – means less chance of biofilm formation and removing a potential food source for the bacteria to feed on.

The presence of hard water should be noted when preparing the legionella risk assessment for the property to identify all potential risks posed by the water system and if risks could be increased by the build-up of scale.

One of the tried and tested methods of controlling limescale buildup in water systems is to use a water softener that works on the ion-exchange method. These water softening systems remove the hardness causing minerals and make the water soft. Water softeners are generally low maintenance, just requiring regular servicing and topping up with the water softening salts.

Various other agents can come into play at this point too, including scale and corrosion inhibitors, dispersants and biocides. Chemicals are another avenue to combat the risk posed by limescale, but alone they aren’t always the best form of defence.

Some biocides are effective against Legionella if used in sufficient concentration. Strains of Legionella and other bacteria may become resistant to particular biocides, hence, dual or alternating biocides are used.

What is required in all the systems—cold, hot, and process—is a method of controlling scale deposition continuously and a water treatment regime that prevents the growth of biofilms, bacteria, and, especially, Legionella pneumophila.

We Offer Specialist Legionella Control Solutions

Celtic Water Solutions offer a wide range of solutions for the pre-treatment of industrial and process water including design, installation and maintenance of water softeners. Over the years, we have garnered a reputation for delivering only the best water treatment solutions to our clients.

Our team of legionella risk assessors is well qualified in the management of legionella risks and support those responsible for the safety of hot and cold water systems in the workplace. All our work is carried out in strict accordance with HPSC’s National Guidelines for the Control of Legionellosis in Ireland, 2009 and UK HSE’s ACoP L8.

Talk to our team of consultants for expert advice.

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