What is a cistern? How does it work?

In the world of sustainable construction and the conscious use of water resources, a key element that deserves highlighting is the cistern. A cistern is a water reservoir used to collect, store, and reuse rainwater. With increasing environmental awareness, the cistern has become an increasingly popular solution, both in homes and commercial buildings. In this article, we will discover how this intelligent and ecologically correct system contributes to the conservation of water resources, as well as promoting sustainability in architecture. Let's go!

What is a cistern? What is its function?

A cistern is a fundamental element in architecture and urban design, playing an essential role in water storage. This structure, which can vary in size and shape, has the main function of collecting and storing rainwater or water from other sources for later use.

In general terms, a cistern is an underground or above-ground reservoir, built with durable and waterproof materials such as concrete, iron, polyethylene, or fiberglass. It is designed to capture and store rainwater that falls on roofs, patios, or paved areas, allowing for its sustainable use. The functionality of the cistern covers several areas, from the preservation of water resources to the efficient use of water in homes, commercial buildings, and public spaces. Let's explore some of the main functions of this system:

• Rainwater harvesting: The cistern is responsible for collecting rainwater that runs off impermeable surfaces, such as roofs. This water, which would otherwise be wasted, is directed to the cistern through gutters and pipes.
• Storage and conservation: The water collected by the cistern is stored for future use. This storage helps reduce dependence on conventional water sources, such as public supply networks or wells. It also helps conserve water resources, especially in areas with water scarcity.
• Non-potable use: The water stored in the cistern is generally used for non-potable purposes, such as irrigating gardens, flushing toilets, cleaning floors, and washing vehicles. This helps reduce the consumption of drinking water and minimize environmental impact.
• Flood prevention: In urban areas, cisterns play an important role in stormwater management, preventing floods and overloads on the drainage system. By capturing and storing rainwater, they reduce the volume of water that quickly flows into sewer networks and rivers.
• Reduction of water costs: Using cisterns for rainwater harvesting can result in significant savings on water costs, especially in large commercial and residential buildings. This is because the collected water is free and replaces part of the drinking water consumption, which is reflected in reduced water bills.

What is the difference between a well and a cistern?

A well is a vertical drilling carried out in the ground until it reaches a layer of groundwater. This layer is called the water table and is composed of water from rain and infiltration. When drilling a well, water is pumped to the surface, allowing its use. Therefore, the water from the well comes from the water table, which can be influenced by the geological conditions of the region.

On the other hand, a cistern is a water reservoir built in or above the ground, usually using materials such as concrete, fiberglass, or plastic. The water stored in the cistern is collected from external sources, such as rain or public supply, and stored for future use. The cistern does not have direct access to the water table and depends on water harvesting through collection and storage systems.

Therefore, the main difference between a well and a cistern is the origin of the water. A well uses the water table as a source of groundwater, while a cistern stores water from other sources, such as rain or public supply. Both structures have their specific uses and benefits, depending on the water needs of a particular area or property.

What is a house cistern?

A house cistern is a water reservoir designed specifically for residential use. It plays an important role in water storage and management, ensuring a continuous supply even in situations of scarcity or interruptions in the public supply. In its most basic form, a residential cistern is a tank or container that can be installed above ground, buried in the ground, or even integrated into the house's structure. It is built with durable and waterproof materials, such as concrete, polyethylene, or fiberglass.

The residential cistern is usually connected to the rainwater harvesting system, allowing direct collection of rainwater that falls on the roofs. Gutters and pipes are used to direct the water to the cistern, where it is stored for later use. The capacity of the cistern can vary according to the specific needs of each residence. They can usually store from tens to thousands of liters of water, providing autonomy and reducing dependence on conventional supply sources.

The water stored in the residential cistern can be used for a variety of non-potable purposes, such as irrigating gardens, washing clothes, domestic cleaning, and flushing toilets. However, it is important to note that this water is not suitable for direct human consumption unless it is properly treated and purified.

Why have a cistern? A residential cistern offers significant benefits to residents. In addition to providing an alternative source of water, it contributes to environmental sustainability, reducing the consumption of drinking water and relieving pressure on public supply systems. Furthermore, it can result in financial savings, as it decreases the use of water from the public network, which is reflected in water bills. Cisterns are also a great solution for dealing with water scarcity in drought-affected areas. The stored water can be used later when needed.

Cistern and sustainability

The search for more sustainable practices in the field of architecture has become a priority in recent years. As awareness of the environmental impacts of civil construction increases, architects and professionals in the sector have sought innovative solutions to minimize these negative effects. In this context, the cistern stands out as a technology that promotes the integration between sustainable architecture and the environment.

The relationship between the cistern and sustainability goes beyond saving water resources. By adopting this technology, architectural projects can reduce the amount of rainwater discharged into drainage networks, minimizing problems related to floods and overloading of sewage systems. This contributes to the development of a more resilient city, capable of dealing more efficiently with extreme climatic events.

In addition to environmental benefits, the cistern also has economic advantages. By reducing the consumption of drinking water, owners can lower their water bills, becoming more independent from public services. Furthermore, in some regions, it is possible to obtain tax incentives and discounts on the water tariff for those who invest in rainwater harvesting systems.

Sustainable architecture seeks to integrate solutions like the cistern harmoniously into projects, considering factors such as climate, topography, and the characteristics of the surroundings. In this way, it is possible to create buildings that relate consciously to the environment, promoting the rational use of natural resources and reducing environmental impacts.

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It is important to emphasize that the use of cisterns as a sustainable practice must be accompanied by good maintenance and water treatment practices. It is essential to ensure that the stored water is treated properly, avoiding health risks. In addition, choosing durable and low-environmental-impact materials and construction systems is also essential to ensure the efficiency and longevity of the system.

So, how does a cistern work? A brief step-by-step guide

• Rainwater harvesting: The first step for a cistern to work is rainwater harvesting. This is done through gutters installed on the roof of the residence. These gutters collect the rainwater and direct it to the downspouts, which in turn lead the water to the cistern.
• Filter: Before entering the cistern, the rainwater passes through a filtration system. The filter's function is to retain leaves, debris, and other solid materials that may be present in the collected water. This helps ensure that the water stored in the cistern is clean and ready for use.
• Storage: The filtered water is directed to the inside of the cistern, where it is stored for later use. Cisterns can be made of different materials, such as concrete, polyethylene, or fiberglass, and have varying capacities, depending on the user's needs. It is important that the cistern is properly designed, with resistant and waterproof materials, to ensure the durability and quality of the stored water.
• Pump and pressurization system: When it is necessary to use the water stored in the cistern, a pump and pressurization system is used. The pump removes the water from the cistern and pressurizes it, allowing it to be distributed to consumption points, such as faucets, showers, and toilets. It is important that the pressurization system is correctly sized to ensure an adequate flow of water at the points of use.
• Water treatment and use: Before using the water stored in the cistern, it is recommended to perform adequate treatment to ensure quality and safety. This may involve the use of additional filtration systems, disinfection with chlorine, or other appropriate methods. The water treatment must be carried out according to the recommendations of the competent bodies to avoid health problems.