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Water Tank Cleaning & Legionnaire’s DiseaseBy:Charles

Nemco Utilities LtdWater Tank Cleaning & Legionnaire’s Disease

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Water Tank Cleaning & Legionnaire’s Disease

Cold water storage tanks can provide the ideal breeding ground for a host of bacteria including Legionella (the bacteria responsible for Legionnaire’s Disease). Typically, water tanks are positioned either above the boiler house or in the loft, which tend to be two of the warmest places in a building this can lead to the water within the tank heating up considerably. In addition, a build up of scale, rust and other contaminants provide nutrients for bacteria which, when added to the above and an over storage of water can create almost incubator type conditions for bacteria to multiply.

With regard to Legionella, although tanks do not create an aerosol themselves they do of course supply services that do, such as showers. It is therefore essential that cold water tanks are kept fresh and free from contaminants to prevent the build of bacteria and biofilm. Biofilm is a layer of bacteria / micro-organisms embedded in a protective layer attached to a surface. This can occur in cold water tanks (e.g. slime along the water line) but also along the inside of pipework. Once bacteria are contained within a biofilm / attached to a surface they change their fundamental characteristics and can become much more difficult to eradicate than free floating bacteria.

For the above reasons it is therefore essential that tanks are inspected regularly and kept clean. When a tank does require cleaning, this should be completed both chemically and physically as a good bit of elbow grease can be the only way to penetrate and get rid of biofilm ( though slightly more tricky if lining the inside of old corroded pipework!).

Nemco Utilities LtdWater Tank Cleaning & Legionnaire’s Disease

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Water system cleaning and disinfection is covered by British Standard 6700 which details approved methods. A large number of water treatment chemicals are available but the gold standard is the use of chlorine. BS6700 recommends a free chlorine concentration of 50 ppm for a contact time of one hour. After the hour, a minimum of 30 ppm should be left to indicate successful disinfection, if the levels are below this then the process must be repeated.

Nemco Utilities have over 10 years experience in water system cleaning and disinfection having completed everything from small domestic water tanks to food factories and large scale water towers requiring specialist rope access.

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