Piping systems/water installations must be thoroughly cleaned (by blowing out and/or the use of pipeline cleaning pigs, etc.) and then disinfected if they are to be made bacteriologically reliable. There are many disinfectants available on the market, such as sodium hypochlorite and hydrogen peroxide. After cleaning and disinfection, samples will have to be taken to show whether these operations have been successful.
In addition to the aforementioned standard chemicals used for the production and maintenance of a quality of water which is bacteriologically acceptable, the following methods can also be considered:

the application of a UV installation: the water to be disinfected is passed through a chamber (unit) where it is exposed to UV light from special lamps. The UV light destroys the bacteria present in the water. The disinfecting action is only present in the UV unit (this is therefore an ‘end-of-pipe’ solution as it has no disinfectant action after the UV unit);
the application of an ozone/chlorine dioxide installation: both ozone and chlorine dioxide are very strong oxidants which are highly effective at achieving bacteriologically reliable water (they also tackle biofilm) and keeping it so. This quality can be maintained by retaining a low concentration of ozone/chlorine dioxide in the water, although any ozone present must be destroyed before the water is used. Ozone and chlorine dioxide are used in most permanent treatment installations.