While Legionnaires' disease bacteria (LDB) contamination is usually associated with large public water systems, the bacteria can also infect small domestic hot water systems. To protect your family from this bacteria's severe pneumonia, you must properly maintain your water heating system.
Conditions that promote the growth of LDB include a temperature below 60°C (140°F), scale and sediment, and water stagnation. To prevent the bacteria from growing, OSHA recommends the following steps:
1. Regular maintenance and cleaning of cooling towers and evaporative condensers.
Clean your cooling towers and evaporative condensers at least twice every year. Use chlorine or other effective biocides to prevent the growth of LDB.
2. Maintain your domestic water heaters at 60°C (140°F).
Homeowners in Utah often lower their water heater base temperature to 120 °F in a bid to slash their energy bills. Such a temperature encourages the growth of LDG. Maintain your heaters at 140°F. The temperature of the water at the faucet should be 122°F or higher. If you're concerned about scalding, use an appropriate fail-safe scald protection.
3. Discourage water stagnation and sedimentation.
Avoid stagnant water in the system through frequent flushing of unused water lines. Periodically drain all the tanks to remove scale and sediment. Beehive Plumbing also suggests maintaining the current water heater or considering options that do not require storing water in a tank.
Treating a contaminated hot-water system
If your hot water has been tested and found contaminated or there's evidence to suggest infection, you should disinfect it. Effective treatment methods include:
• Pasteurizing the system by heating the water to a minimum of 70°C (158°F) and flushing all the faucets with hot water for five to 20 minutes.
• Cleaning the system with an appropriate chemical disinfectant or an acceptable biocide treatment.
With about 10,000 to 50,000 Legionnaires’ disease cases reported in the United States each year, the disease is a real health concern. Since LDB thrives in warm, stagnant water, do an audit of your water heating system to identify the design and maintenance solutions that can keep the water hot and flowing. Regular testing also contributes to detecting the bacteria to enable early eradication.