Legionnaires is only a problem if you breath it in. Theoretically you could drink water with legionnaires bacteria in it (although probably not recommended) and it won't give you legionnaires disease. It's when you get it into your lungs in a warm moist atmosphere is when you are at risk. This is why it can effect people who use showers (like at a hotel) that haven't been used for a long time. You crank up the heat creating steam that you breath in. My parents neighbour died from it after catching it at his home.
If in any doubt add a bit of bleach (or similar chlorine based products)
Edited by jamesmpi, 06 November 2016 - 06:21 PM.