In normal water systems, treated water from the water treatment works is normally stored in one or more reservoirs. Reservoirs allow temporary storage of water and assist with meeting peak demands. In addition by having sufficient storage, supply to consumers can be ensured even during times when breakdown and subsequent repairs occur. These reservoirs are normally located on hilltops or in elevated structures allowing water to flow into the reticulation system and consumers homes via gravity (i.e. no need for pumping, reduce operating costs). In smaller systems this may not be possible and pumps may be required to transfer water to consumers.
In order to ensure that the quality of water leaving the water treatment works ends at the consumers tap, it is necessary to maintain and renew the distribution network infrastructure (including storage facilities and pipelines). Water systems that are not appropriately maintained can result in the deterioration of the drinking water quality, which may impact on human health. Storage reservoirs therefore need to be cleaned on a regular basis. It is therefore essential that sufficient storage capacity is available such that a reservoir can be taken out of operation for maintenance and repairs.
In addition, disinfection can occur in reservoirs in order to limit bacterial re-growth ensure that the water reaching consumers is free from pathogens.
Finally, of critical importance is that reservoirs are protected from interference from humans and animals. This includes securing the reservoir site (fence, lock), keeping the area surrounding the reservoir clean (no litter, grass cut) and ensuring the reservoir is covered (roof, lid closed).
The following types of storage facilities are generally found:
Concrete - One of the most effective storage solutions, but initially capital intensive.
Plastic/Fibreglass - Usually constructed of polypropylene or fibreglass. Often used for smaller water supply systems. Care should be taken to ensure structures do not suffer from UV degradation in sunlight.
Metal - Also often used for smaller water supply systems. The quality of the water supplied to the tank must ensure that corrosion of the metal tank is minimised, as this can give rise to undesirable corrosion by-products in the distribution network.