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Cistern

technology Maturity 9-11 Next article →

A cistern is a waterproof receptacle designed to hold liquids, most commonly fresh water.

Well-cistern
Well-cistern

While they are often confused with wells, they function through different principles. A well draws water from groundwater located deep beneath the earth. In contrast, a cistern collects and stores water from other sources, such as rainfall.

Red rain barrel
Red rain barrel

Because they must hold liquid without losing it, the interiors are often lined with hydraulic plaster. This specialized plaster creates a waterproof seal to prevent leakage. Modern cisterns vary greatly in scale, ranging from small containers of a few liters to massive reservoirs holding thousands of cubic meters.

The mechanism of a cistern depends on how it collects its supply. Many systems utilize rainwater harvesting to fill the container. In regions like Bermuda, white-stepped roofs serve as the collection surface.

Bermuda roof
Bermuda roof

Gutters channel the rain from these roofs into underground cisterns. Other cisterns are filled manually, by truck delivery, or by wells using electric pumps. In some cases, the water is filtered before it enters the storage area. For example, a filter cistern uses a sand filter to clean the water. This process can also enrich the water with minerals as it passes through the sand.

Cisterns can be categorized by their design and purpose. Tank cisterns are basic storage units, while filter cisterns include integrated cleaning mechanisms. In residential settings, cisterns can be mounted on top of houses to supply running water. They can also be built into walls, known as concealed cisterns. In modern plumbing, the toilet uses a small cistern to hold the exact amount of water needed for a flush.

Gravity toilet valves handle down
Gravity toilet valves handle down

These can be close-coupled, meaning they sit directly on the bowl, or they can be located high above the bowl and connected by a pipe.

Humans have engineered water management systems for millennia. During the Neolithic period, village sites in the Levant featured lime plaster cisterns in house floors.

Medium sized rock cut cistern at pavuralla konda at bheemunipatnam
Medium sized rock cut cistern at pavuralla konda at bheemunipatnam

In ancient Israel, large cisterns were carved directly into bedrock, such as the one found at Tel Hazor. These were often located beneath palaces during the Late Bronze Age. The Romans further advanced this technology with the impluvium. This was a standard feature in a Roman domus, or house. The impluvium collected, filtered, and cooled water, which also helped ventilate the home.

In the Middle Ages, cisterns were vital for survival in European hill castles. These were often built when wells could not be dug deep enough to reach groundwater. Today, cisterns remain critical in areas where water is scarce or depleted. In San Francisco, the city maintains a massive Auxiliary Water Supply System (AWSS) for firefighting.

Water cistern in San Francisco
Water cistern in San Francisco

This network includes 177 independent underground cisterns. They have a total capacity of over 100 million gallons. These cisterns are separate from the main water supply to ensure water is available even after an earthquake.

Large-scale programs demonstrate the social significance of these structures. In Northeastern Brazil, the One Million Cisterns Program (P1MC) helps small farm-holders manage water.

Unterirdische Zisterne
Unterirdische Zisterne

Launched in 2013, this program uses cement-layered cisterns to harvest rainwater from rooftops. Each cistern holds 16,000 liters. This amount can sustain a family's needs for drinking and cooking during the dry season. By 2016, 1.2 million of these cisterns were implemented for human consumption. The government even expanded this into the "One Land, Two Water Program" to support agricultural production.

Maintaining water quality is essential for any cistern used for consumption. Users must keep them well-enclosed to prevent algae growth or mosquitoes, which can carry disease. Regular inspections and cleaning with a proper dilution of chlorine are recommended. If the water quality is uncertain, it may still be used for non-drinking tasks like irrigation or flushing toilets. In some Southeast Asian countries, small cisterns are even built into bathrooms to support traditional bathing methods. From ancient bedrock carvings to modern plastic tanks, the cistern remains a fundamental tool for managing life's most precious resource.

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🖼️ Images & Media (11)
File:El Jadida cistern.jpg
El Jadida cistern.jpg
File:Well-cistern.jpg
Well-cistern.jpg
File:Cistern in the Mission District, San Francisco, California.jpg
Cistern in the Mission District, San...
File:Water cistern in San Francisco.jpg
Water cistern in San Francisco.jpg
File:Medium sized rock cut cistern at pavuralla konda at bheemunipatnam.jpg
Medium sized rock cut cistern at...
File:Citernes malga interieur.jpg
Citernes malga interieur.jpg
File:Unterirdische Zisterne.jpg
Unterirdische Zisterne.jpg
File:Bermuda roof.jpg
Bermuda roof.jpg
File:Gravity toilet valves handle down.svg
Gravity toilet valves handle down.svg
File:Basilica Cistern, Constantinople.jpg
Basilica Cistern, Constantinople.jpg
File:Red rain barrel.jpg
Red rain barrel.jpg
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