cistern

A cistern is a watertight container designed to store liquids, most commonly water. Cisterns are used to collect, store, and distribute water for domestic, agricultural, industrial, or ceremonial purposes. They can be built into a building, embedded underground, or placed above ground, and they often rely on gravity to supply fixtures or, in modern installations, on pumps for pressurized delivery.

Common types include rain cisterns, which collect runoff from rooftops, and potable water cisterns that store drinking water for household use. In plumbing, a toilet cistern is a small storage tank that releases a measured amount of water with each flush. Large cisterns have been used historically in cities and fortifications to ensure a reliable water supply during sieges or droughts.

Construction materials vary and picture a range from stone, brick, or concrete to metal linings or waterproof coatings. The interior is typically sealed to prevent seepage and contamination. Cisterns may incorporate screens or filters to reduce debris and may be fitted with vents, pumps, or float valves to control water level and delivery.

Operation and maintenance focus on keeping water clean and free from stagnation. Regular cleaning, sediment removal, insect control, and protection from sunlight help prevent algae growth and microbial contamination. Regulations may govern the construction, use, and labeling of potable-water cisterns to ensure safety and health. In heritage contexts, cisterns appear in ancient architecture as practical water reserves.