Preventing legionella contamination through insulation

Preventing legionella contamination through insulation

Armacell insulation materials protect hot and cold water pipes against unacceptable temperature fluctuations which can occur during the summer when the risk of legionella also rises. During holiday periods water stagnates in pipework, making HVAC and plumbing systems an ideal breeding ground for hazardous bacteria.

Legionnaires’ disease is an underreported and severe form of pneumonia transmitted by pathogens in water, with an estimated 10,000 - 20,000 cases per year.

Contaminated air-conditioners, swimming pools or whirlpools and cooling towers are well-known sources of infection. Errors made in the design and installation of sanitary systems can also lead to a dangerous rise in legionella in drinking water as well as fountains, sprinkler systems and humidifiers for food display cabinets. Therefore, one of the most important preventative measures is to insulate both hot and cold water pipes using suitable materials.

Legionella are bacteria which can get into the drinking water systems of large buildings through the central water supply. They are particularly likely to multiply in stagnant water at temperatures between 25 and 45°C. The bacteria become hazardous when they are inhaled as small droplets.

A combination of measures are available to prevent microbial contamination. Apart from ensuring that the water circulates continuously through the pipework, it is also necessary to prevent unacceptable temperature decreases in hot water pipes and increases in cold water pipes.
According to the European standard BS EN 806-2, pipes for cold drinking water should not follow the same routes or run adjacent to space heating or hot water pipes. Cold water pipes should be protected against heat gain by ensuring sufficient clearance or preferably by insulating properly.

When hot and cold pipes are laid in one duct or wall cavity, or wherever water is not circulated regularly, Armacell recommends using what is known as 100% insulation, i.e. an insulation thickness which roughly corresponds to the pipework outer diameter. On hot drinking water pipes this not only prevents legionella, but also protects the pipes against unnecessary energy losses. On cold water pipes the insulation provides protection against freezing in cold weather as well as providing protection against unwanted temperature rises.

Suitable insulation materials also prevent unwanted condensation. Because of the risk of condensation, only closed-cell insulation materials with a high resistance to water vapour diffusion should be used on cold drinking water pipes. In practice, accidental damage to insulation has shown that open-cell insulation materials (no matter whether with or without a vapour barrier) do not sufficiently prevent moisture ingress as a result of diffusion. With open-cell materials the resistance to water vapour diffusion is concentrated on the vapour barrier, so even if the systems are installed carefully, water ingress can often not be avoided. This means that there is a danger of water vapour in the air penetrating the insulation, condensing and saturating the insulation material. As the material becomes damp, the thermal conductivity increases and insulation properties deteriorate, causing a rise in energy losses. Furthermore, corrosion and other expensive consequential damage can occur.

Armacell insulation materials including AF/Armaflex Class O, Armaflex Tuffcoat and Tubolit protect pipes against temperature increases and decreases.

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Armacell UK is the world's leading manufacturer of flexible elastomeric foams and technical thermal and acoustic insulation materials for pipe work, valves, vessels and fittings. Based in Oldham, Armacell UK manufacture the renowned AF/Armaflex...
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