The system of pipes and tanks that store and convey water following treatment to consumers’ taps is known as a distribution network. These systems may also include valves, hydrants, pumps, connection facilities and inspection points or other fittings for control and/or maintenance purposes. Even where effective treatment is used to secure a wholesome supply of drinking water, its quality at the point of consumption may not be wholesome if the integrity of the distribution system is compromised.
The arrangement of distribution systems can be extremely variable, both in terms of their complexity and physical construction, and can range from simple single length pipe runs to larger more complex systems that are difficult to trace. In either case, even small networks can span distances from a few meters to several miles. Consequently, the number of potential or actual hazards present in any distribution system can be numerous, diverse and variable. In turn the risks that these present can and will have a direct bearing on water quality if the system is not adequately constructed, managed and/or maintained according to its layout and design, irrespective of its age, which in some cases might be significant.
Risks to water quality can be mitigated and controlled by an awareness of the hazards and sensible and simple management and maintenance of the system. For example, routine cleaning of storage facilities, having suitably sized robust and covered storage tanks and reservoirs, periodic flushing of the system through taps and hydrants and the use of approved water fittings (plumbing parts and substances). The inclusion of backflow protection devices such as check valves are also an essential component of any distribution system to prevent contaminants being sucked or pushed into the system through pressure differentials.
The identification of risk on any distribution system can be difficult owing to the pipes and tanks often being underground or hidden, which hampers inspection. Therefore the water quality impact of deficiencies in a distribution network may not become evident until it manifests, either through monitoring (sampling and analysis), or more usually through objectionable taste, odour or appearance at the point of consumption.