Rainwater Collection Systems: A Tool for Sustainable Construction

Rainwater collection system

A rainwater collection system consists of a set of mechanisms that include channels, tubes, filters, tanks, pumps, and others, to capture, conduct, store, treat and use this resource, both for drinking purposes (consumption and human contact) as not drinkable (sanitary, irrigation, industrial use, cleaning, etc.).

This practice, which has been carried out since ancient times, is used today in various parts of the world as a measure to combat water scarcity and promote the sustainable use of water resources in a context of climate change. An example of this is Mexico City, where in recent years policies have been implemented to promote this measure.

How does a rainwater collection system work?

A rainwater collection system operates through several key components. The following are the basic steps of the system, which may vary depending on the specific use and size of the building:

1. Collection: rainwater is collected, usually the roof of the building is the catchment surface. The water is directed through the gutters installed on the roof edge.
2. First rain diverter: this component is often used to divert the first rains, which are usually more contaminated with dust and other debris. Even if the water is for non-drinkable use, the diverter will be useful to keep the water cleaner.
3. Downpipe or downspout: is used to connect roof gutters to the cistern or storage tank.
4. Filtering: before water enters the storage tank or cistern, it is recommended to pass it through an additional filter to remove large particles and contaminants, as well as to reduce the accumulation of sediment.
5. Storage tank or tank: can be made of materials such as plastic, metal or concrete and can have one or more compartments. Generally, they have an access well for easy maintenance and cleaning.
6. Distribution: after being stored, the water can be pumped into the house or building using a pump. If the tank is located at a sufficient height, the water can be distributed by gravity.
7. Use: the rainwater collected will be used as needed, for example, for garden irrigation, laundry and even for human consumption if it has been properly treated.

What are the benefits of installing a rain collection system?

Environmental Benefits

• It increases accessibility to water locally by eliminating the need to transport it over long distances.
• It alleviates pressure on aquifers and other sources by reducing water extraction.
• It reduces runoff to drainage systems and streets during heavy rains, alleviating the burden on hydraulic infrastructure and reducing the risks of waterlogging and flooding.

Economic benefits

• The cost of incorporating the rainwater collection system is almost completely concentrated on the initial installation. The return on investment will vary depending on the cost of the system and the supply of water from other sources. This will be greater in situations where water is expensive, pre-existing storage is used, the roof surface is large or the system is integrated into a new construction project.

Benefits for society and health

• The main benefit, in most cases, is the improvement in the availability and quality of water, which has a positive impact on quality of life, hygiene standards and human health.
• It can provide very high quality water, provided that a system is used to capture rainwater that is properly designed and installed, and that the system and the roofs are properly maintained.
• It promotes a culture of efficient use and conservation of water resources.

What are the limitations of collecting rainwater?

• In places with less than 400 mm of average annual rainfall, collection will not generate significant results.
• In places where rain is seasonal, harvesting cannot be the only source of water.

Sources consulted: Harvesting the rain, Manual to install it in your home. Handbook for Rainwater Harvesting for the Caribbean. A practical guideline featuring best practices for rainwater harvesting in small island Caribbean environments.