Like they say, "What you don't know could kill you." Legionnaires' Disease just sounds like something your grandfather got during the "Great War". Unfortunately it is much more modern and death occurs in about 30% of the cases. It was identified in the late 70's after 34 people died and 221 were infected with a bacterium that produced pneumonia like symptoms during a Convention of the American Legion. Of the 221 infected, 72 were people not involved with the American Legion convention but had either been inside the Bellevue-Stratford Hotel or had walked past it. The Legionnaire's disease bacillus was actually spread by the air conditioning system in aerosolized water droplets.
Legionnaires' Disease is basically pneumonia. I am not a doctor and this may be an overgeneralization but symptoms occur 2-10 days after exposure and treatment is the same as pneumonia. The good news is that it is not spread person to person. Legionella is spread by aerosolized water contaminated with the bacteria. Identified sources of contaminated water include water storage tanks, stagnant water, infrequently used water lines or dead leg water lines (emergency eyewash and shower stations, fire sprinkler systems), saunas, hot tubs, etc. Key factors in water contamination include:
- Temperatures between 20° and 50° C (68° - 122° F) (The optimal growth range is 35° - 46° C [95° - 115° F])
- pH between 5.0 and 8.5
There are other factors but these are the ones that you see most frequently in home water storage. Chlorination is not an effective treatment for the water. CDC recommendation of identified sources includes chlorination, and at least 30-minute high temperature flush of all water lines. Multiple system flushes have been ineffective in some cases.
Bottom line is if you have a storage tank water heater it needs to be set to deliver water at temperatures higher than the current industry standard. Water needs to be stored above 140° F and deliver water at temperatures above 122° F. Unheated storage tanks are at particular risk. Kept in an attic or garage in the south storage tanks can easily reach temperatures above 100° and even tanks kept in a basement or other cool area rarely stay below the recommended 68° F. Copper pipes seem to reduce the growth rate of the bacteria but plastic pipes increase the risk of bacterial growth, as does rubber in gaskets or wood from cooling towers, saunas, and spas. Showers, spray nozzles, fire sprinklers, yard sprinklers, and back yard spas are all areas that can produce the aerosolized water droplets that transmit the bacteria to the lungs.
Here are a few links for further research:
See ASHRAE Guideline 12. There are free sources for this standard online.
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