Risk of Legionnaires’ from various water sources?

1) Would a clogged roof drain leaking into an office pose a non-risk, low risk, or high risk of causing Legionnaires’ disease in a worker in that office?


2) Would a drinking fountain (lower than 68°F) be a suspect source? What if the temperature was not always maintained below 68° (water was above 68° but then returned below 68°)? Could the water be contaminated even though it is now below 68°?


3) What is the likelihood of contracting Legionnaires’ from a bathroom faucet when washing hands?


4) If bottom of hot water heater is much cooler than the upper layer of water, which is what goes into the hot water system, why would the lower water be of concern? 


5) If the hot water heater is off for a few days, then is back on and delivering water at 122°F-140°F, could the water at the faucet still be contaminated with Legionella?


1) Non-risk

2) It would be a low risk. Temperature becomes a factor mainly when it is between 120°F – 140°F, the optimal temperature for propagation of Legionella.

3) No risk.

4) The temperature is conducive to growth of Legionella mainly between 120°F – 140°F. If the hot water tank was at this temperature, it is possible that it could become contaminated.

5) Yes