An ideal means of ensuring the cleanliness of drinking water is to use chlorine dioxide as a disinfectant. Chlorine dioxide is highly effective against all types of germs and has a long dwell time in the system, which means it disinfects even without extracting water. The big advantage of chlorine dioxide over other disinfectants is its effectiveness against biofilms.
It actually destroys the existing biofilm, thus removing the breeding ground for the Legionella, and prevents it from building up again.