A water supply system should include some form of treated water storage to provide a reserve of drinking water to cater for fluctuations in demand, timeout for planned maintenance or any problems. Storage may take the form of a small covered reservoir, providing sufficient head to supply more than one property, or may be a suitably positioned storage tank (e.g. in the roof space of the property), from which water flows under gravity to the taps.
Design of water storage
The tank or reservoir should hold a volume sufficient to accommodate the peak demand and the maximum period of interruption of supply, but must not be so large that water is allowed to remain static for lengthy periods because allowing the water to stagnate and develop aesthetic issues.
All storage tanks must be insulated to guard against freezing during the winter and excessive warming during the summer months. The tank must be fitted with a robust lockable, and well fitting (but not airtight) lid to exclude light and pollutants. It is especially important to prevent the ingress of insects and animals and all openings must be protected using a fine mesh screen.
Commissioning water storage
The storage tank and other parts of the water supply system may be contaminated during construction and should therefore be disinfected before use. This is achieved by filling the system with a 20 mg/l solution of chlorine and leaving it to stand for several hours, preferably overnight. The chlorine solution should then be drained off and the system rinsed thoroughly using treated water.
Maintenance of water storage
The storage tank must be inspected regularly; at least annually and preferably every six months. If necessary, any accumulated silt can be flushed or siphoned out and the system disinfected as described above.