Determining if your building is at risk starts with identifying the systems, devices, and areas where Legionella bacteria can spread to people. It is also important to identify the factors throughout the water systems and equipment that can promote Legionella bacteria growth and exposure. Today, it is even more important to complete this assessment in that many sites are operating at reduced capacity and there are areas of buildings with limited use.

At Risk Systems and Equipment

  • Cooling Tower Systems
    • Evaporative Condensers
      • Hot and Cold water storage tanks
      • Expansion tanks
      • Dead Leg sections of system’s piping
      • Decorative fountains
      • Hot tubs
      • Ice machines
      • Misters, atomizers, air washers
      • Infrequently used equipment such as eyewash stations, faucets, showers

There are many factors present in buildings water systems and equipment that promote an environment ripe for Legionella bacteria growth and exposure. It is important to start with the initial point of entry for the buildings water supply and then to trace the movement of the water across the various systems and pieces of equipment. Listed below are some of the most important factors attributed with Legionella bacteria growth and exposure.

Important Risk Factors to Identify

  • Disinfectant residual of water
    • Initial point of entry for building water supply
    • Disinfectant Residual of water at various points of system
  • Stagnant water conditions
    • Dead legs and low flow sections of piping
    • Age of water increases probability of bacteria growth
    • Rarely used fixtures and equipment such as showers, faucets, eye wash stations
    • Sites that have reduced building occupancy
  • Fluctuating Water Temperatures in water systems
    • (77 ⁰ F –  108 ⁰ F )  temperature for Legionella bacteria growth
    • Low temperature settings on HW systems
    • Loss of heat as water travels further from heat source
    • Sites of Cold and Hot water mixing
    • Areas of heat transfer when cold and hot water pipes are too close together
  • Presence of Biofilm on system piping and equipment
    • Can protect Legionella bacteria and other bacteria from disinfectants and heat
    • Provides a food source for bacteria growth
  • Scale and Sediment Buildup
    • Protects and can insulate bacteria from disinfectants and higher temperatures
    • Higher dosages of disinfectants needed to penetrate through scale, dirt, and sediment
  • PH of water systems
    • Determining pH of water in each of the systems
    • Disinfectant most effective within a pH of 6.5 to 8.5 range

Now that you have identified your buildings water systems, equipment, and potential risk factors present it is now important to develop a Water Management Plan that adheres to the ASHRAE 188 standard and provides steps to implement strategies and control measures that will reduce the risks of Legionella bacteria growth and exposure at your site.

Corrosion Technology Inc. provides water treatment programs and strategies that adhere to the ASHRAE 188 standard and CDC guidelines for protecting people from contracting Legionnaires’ Disease. We can provide the resources and guidance in developing a water management plan and developing a team assessing the risk factors at your site and implementing control measures that mitigate growth and exposure to legionella bacteria.