Legionella In Water Tanks


Legionella Pneumophila is a bacteria typically found in water. It is the cause of Legionnaire’s disease that attacks the lungs, and results in potentially fatal pneumonia. People contract the disease by breathing in the tiny droplets of water containing the bacteria.

Our GRP water tanks are manufactured with corrosion-resistant material, which aids in the prevention of Legionella in water tanks. This makes our water tanks ideal for storing safe, potable water for your residential or commercial building. Read on to discover more about our range of insulated water storage tanks that can control the water temperature and the importance of keeping your tanks clean to avoid Legionella or other waterborne diseases from polluting your water supply.

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What Is Legionella?

Legionella is a dangerous waterborne disease with different strains that attack the lungs, making it a severe health risk.

Legionella thrives in stagnant water, so it is commonly found in ponds or lakes with warm temperatures. However, it can also be found in your water storage tanks if the installation was carried out incorrectly or if the material used to manufacture the tank allows the bacteria to multiply. Legionella in water tanks grows due to the temperatures being between 20-45°C. The bacteria will be inactive if the cold water storage tanks are kept under 20°C. Purchasing an insulated water tank from us means your water will not be at risk of reaching the temperatures that create the perfect environment for the bacteria to grow.

Legionella in water tanks typically causes sickness in these vulnerable individuals:

• Smokers
• Alcoholics
• Elderly
• Diabetic
• Suffering from cancer, or a chronic respiratory illness
• Immunocompromised

Legionella disease can be easily transferred between patients in hospital settings.


Tricel is an experienced manufacturer of high-quality GRP water tanks with a proven track record of successful projects completed across the UK. The GRP material used to construct our cold water storage tanks helps to keep the water supply safe from contaminants common with alternative materials such as steel or aluminium. Our WRAS Approved water storage tanks are designed to keep Legionella from growing and spreading in your water supply.

Tricel has fully trained and certified installation teams under the European Technical Guidelines for Legionella prevention and control.


Some modifications can be done on a cold water storage tank to minimise the risk of waterborne diseases, such as Legionella breeding inside your water supply. All connection points must be high quality and have no unnecessary, visible openings.

Water tank connections and spare parts must be purchased from approved manufacturers. Screened air vents and lids may also be purchased to prevent contaminants from entering the water supply.

AB air-gap break tanks are secure water storage tanks designed to prevent backflow into the system. It is a closed tank fitted with an air-gap. The purpose of break tanks is to stop the main water supply from being contaminated, which is essential in protecting potable water.

GRP sectional water tank


Our GRP water tanks are the right solution if you want to upgrade your current water system or an old, low-quality cold water storage tank. The risk of Legionella in water tanks is higher if the tank is old and made of low-quality material.

A one piece tank is sufficient for applications with lower water demand, whilst larger-scale operations would ideally require a sectional tank.

Our sectional tanks can be rectangular, square, or L-shaped to accommodate your installation conditions. You can also choose from various internal and external flange options to suit varied amounts of plant room space.

Choosing the Right Water Tank

Selecting the right water tank is the first and most crucial step in Legionella prevention.

First, analyse the space requirements and water usage to determine whether you need a one-piece, sectional, or TIF tank. We have a helpful tank size calculator tool to assist you in working out an accurate estimate of the tank size you need.

Second, select a water tank made up of UV-stabilised material to prevent the inside of the tank from corroding. A rusting water tank is at a higher risk of contamination.

Third, install a water pump or pressure booster set to eliminate stagnation. Water that is constantly moving helps minimise the risk of Legionella in water tanks by reducing biofilm buildup.

Fourth, choose a water storage tank that is easy to maintain, such as our one piece tanks – these are an ideal choice for people with limited time to carry out regular inspections and tests.

Case study sectional tank image


Water Testing

Testing your water supply is a vital part of the maintenance protocols. It is advised to check your cold water storage tanks for contamination and consider testing the water, especially for high-risk systems.

Tests must be carried out in more than one part of the tank because Legionella may be concentrated in one particular area of the water tank before spreading to other parts. The system needs to be flushed to remove any areas of stagnant water which will disrupt the growth of Legionella and prevent any biofilm buildup.

Test and flush your water system if:

• Your water system or water storage tank is old
• Your water system is at higher risk for contamination
• Anyone in your household, business, or facility is immunocompromised or at high risk for contracting Legionella disease
• You find biofilm sediment building up inside

To sanitise the tank, a contaminated water supply requires copper or ionisation or a biocide treatment such as chlorine dioxide.

Water Tank Cleaning

Annual inspections of your cold water storage tank can determine whether the tank needs to be cleaned. This is not a legal requirement to clean a tank, but to minimise the risk of Legionella in water tanks, it is advised. It is a practice that must be taken seriously in domestic and commercial settings to maintain a safe, high-quality water supply.

TIF tank installation

Legionella Prevention

Taking prevention measures early against Legionella will help you avoid having to take potentially costly actions once it is discovered in your water supply. To keep the Legionella bacteria out of your water supply, follow these steps:

• Buy only water tanks made by an approved manufacturer
• Streamline your plumbing to ensure there are no unnecessary openings in your tank
• Purchase insulated tanks to keep temperatures at 20°C or lower
• Clean and maintain your water system regularly
• Use only appropriate, adequately installed plumbing materials
• Fit tanks and pipes with screens, lids, and other barriers to prevent contamination where appropriate


Adding chlorine to your water tank can prevent the growth of Legionella. Ratios have to be measured carefully to avoid creating a toxic water supply.
To use chlorine for Legionella control in your tank, add four parts chlorine for each 1,000,000 parts water. When in doubt, hire a professional to treat your tank to ensure the correct proportions are used.

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