Preventing Legionella Growth In Your Water Tank Systems

Legionella is a potentially fatal bacteria if inhaled via airborne water droplets. This affects people in the form of Legionnaire’s Disease, which has symptoms similar to pneumonia, but is preventable if a series of control measures are put in place.

The Legionella bacteria is naturally occurring, and while it can be found in domestic water systems, it most commonly colonises in man-made water systems where the temperature range provides ideal conditions. These are generally temperatures between 20 to 45 degrees Celsius and where the water has a pH value between 5.0 and 8.5. Below 20 degrees Celsius the bacteria is dormant and above 60 degrees Celsius the bacteria won’t survive.

Many industrial plants and commercial units use water for varying purposes in production or service processes, and they are required to carry out risk assessments and implement strict measuring, dosing and cleaning procedures to monitor for Legionella bacteria. Common processes where the bacteria can flourish are:

  • Hot and cold water outlets
  • Hot and cold water storage and recirculation systems
  • Atomisers
  • Wet air conditioning plant
  • Whirlpools or hydrotherapy baths

Risk Assessments

Depending on the nature of the water system you have there are various different control measures you can implement, but common to all systems is the need to carry out a suitable legionella risk assessment. This should include:

  • A list of all systems and equipment involving water on site
  • Current standards of cleanliness
  • Sampling currently undertaken from all relevant outlets
  • pH measurements
  • Temperature measurements
  • Identifying sources of risk in the systems
  • List the control measures currently in place
  • Document the procedures and best practice

Control Measures

Other control measures that should be considered include:

  • Hot water tanks should be maintained and distributed at a temperature of 60?C or above
  • Cold water tanks should be maintained and distributed at a temperature of 20?C or below
  • A competent person or third party contractor should routinely check, inspect or clean the system, including taking samples for analysis
  • Distribution temperatures should be checked regularly
  • Legionella grows rapidly in stagnant water so systems should be designed to remove dead legs and dead ends where water can sit for long periods. It helps to flush your system out completely on a regular basis, but it also helps to minimise pipe lengths and make them as direct as possible
  • Insulate pipes to maintain water at the temperature desired
  • Some water systems are used as a re-circulating cooling tower, in order to cool machinery and equipment in operation. In this system cold water is fed in but warmer water returns to the tank. To prevent Legionella growth, biocides are dosed into the system to maintain the pH where it needs to be. This is required to be routinely monitored and the system maintained, again, often by a qualified third party contractor. A separate risk assessment is recommended for this process also
  • Legionella bacteria grows where scale or sediment accumulates in a water tank, so regular cleaning is required to prevent or remove this.

Water Hygiene Services can advise on the potential for Legionella growth in your water systems and we can consult with you on the best methods of controlling any risks in the future. This can only be done by understanding your individual system and system needs, and we can tailor our advice to ensure you are presented with a custom-made solution. Click here to contact us today.