Filtration of the incoming water to site/building is used to protect the whole building, including the processes and staff within. It is common practice for water sources other than mains feed and is also used with mains feed when the site is, for instance, a food factory, hospital or manufacturer of beverages.
Depth cartridges protect pipework and equipment from clogging. Surface cartridges are used to remove specific contaminants such as cryptosporidium and bacteria. Softening systems prevent scale build-up, UV systems reduce biofilm growth rates and in some cases, RO systems are used if the source water has a range of unwanted contaminants.