To protect the water from contamination, the reservoir is covered with a roof, usually made of reinforced concrete, but other materials can be used. In the top of the tank an aeration pipe with a screen allows fresh air to circulate in the tank, but keeps rodents and
insects out. A manhole in the roof allows access to the tank for cleaning and repairs. Water flows into the reservoir through an inlet pipe above the water level in the reservoir. This prevents back-flow and allows the water to be heard entering the tank. At this point, a chlorine solution is often added for disinfection. Outlets are built a little above the floor of the reservoir, which has a slope pitched down towards one point with a washout pipe for flushing.
==Suitable conditions==
''Use'': For reservoirs larger than about 3 m3 where sand, cement, gravel and reinforcing materials are available.
==Construction, operations and maintenance==
[[Image:reinforced concrete reservoir.jpg|thumb|right|300px|Reinforced concrete reservoir diagram. Photo: WHO.]]
'''Range of depth''': Usually between 1.5–3.0 m.
'''Expected useful lifetime''': 30 years.
Operation consists of opening and closing the valves, and managing a chlorinator, if provided. If the reservoir does not deliver directly to a tap, water distribution is usually carried out by a caretaker. A well-designed and well-built reservoir needs very little maintenance. The surroundings must be kept clean on a regular basis; every two months the valves must be closed and opened to prevent them from sticking, and the screens must be checked. Occasionally, a screen or tap may need to be repaired. Once a year, or sooner if contamination is suspected, the reservoir must be drained, de-silted, cleaned with a brush and disinfected with chlorine. Any leaks or cracks in the concrete have to be repaired as soon as possible. If needed, a caretaker can be appointed to regulate the inflow and outflow. A concrete reservoir has few other organizational requirements.
