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Guide to Rainwater Collection Systems                                 

In recent years, rainwater collection systems have become popular as the effects of climate change increase and different parts of the world experience droughts and groundwater depletion. Collecting rain and storing it for reuse has become a viable way to supply households and businesses with water. 

While we have modern rainwater harvesting systems today, it is an old practice. Essentially, a rainwater collection system could be as simple as harvesting rain from a roof surface and collecting rainwater in a storage vessel. It is an easy way to conserve water while you save costs.   

If you want to learn about rainwater harvesting and creating one in your home, read on as we take you through our beginner’s guide to rainwater harvesting systems.   

How does a rainwater harvesting system work?

rain barrel
Photo by Arlington County on Flickr licensed under CC BY-SA 2.0 (Cropped from original).

So, how does a rainwater harvesting system work? Well, the most basic rainwater harvesting systems typically consist of a way to collect rainfall as simple as the roof of a building, a system to direct the water (this could be a gutter), and finally, a place to store rainwater, (like rain barrels). This system doesn’t have a filter, so collected rainwater will be more suitable for basic things like watering plants.

A rainwater collection system can be more complex, with several layers of filters to remove the dirt and debris from the water supply. These systems also have a rainwater storage tank to capture the large water inflow. 

An ideal storage tank should be large enough to store rainwater without overflow and made with materials that won’t leach into the water. Finally, this rainwater harvesting system may come with pumps to help distribute water, an overflow prevention system, and a flow meter. 

Related Read: How Is Rain Formed? What Are Rain Gardens?

How much rainwater can you collect?

You can use the following formula as outlined by The Federal Energy Management Program to calculate how much water you can collect through rainwater harvesting systems: 

Monthly Rainfall Collected (gal)

= Catchment Area (roof size)(square feet) × Monthly Rainfall (inches)

× Conversion Factor(0.62) × Collection Factor(75%-90%)

To calculate rain collection, you will need to find the length and breadth of your roof and calculate the total square foot. Secondly, you will need to find the average monthly rainfall in your area. You can check local meteorological services for this data. Once you have this information, plug the numbers into the formula. 

For example, if the monthly rainfall is 4 inches for a 1500-square-foot roof area, the calculation will be: 

1500 x 4 x 0.62 x 75% = 2790 gallons per month. 

With this formula, you can determine whether installing your own rainwater collection system is beneficial, taking into account factors like the cost of water. 

Methods to harvest rainwater

There are various techniques for harvesting rainwater, from simple methods you can do yourself at home to complex systems that require professional installation. When choosing a method, consider what you will be using the harvested rainwater for. 

This will help you decide how much filtration you need. For example, if you collect rainwater for outdoor purposes like gardening, you won't need as much filtration as you would if you were using it as drinking water. 

Rooftop rainwater harvesting 

Photo by Taylor Hammersla on Unsplash.

This is a simple method you can try out at home. This system collects rainwater from a roof, which serves as a collection surface. It then moves through downspouts and stores the rainwater in a rain barrel or tank. All you need to do is place the rain barrel at the bottom of the spout and have rainfall go through the system to provide a water supply. 

This type of system doesn’t require much maintenance. You will only need regular gutter cleanings and cover your rain barrel with a lid to prevent large debris and animals from entering. 

Surface runoff harvesting 

If you’re collecting water for household use, such as washing and toilets, or outdoor use, like watering a garden bed, irrigation, or a swimming pool, this can be an excellent method for harvesting rainwater. This system moves rainwater from a flat surface through a pipe and into a storage tank. 

It will also require a downspout filter or maybe two filters for additional filtration. These filters will require monitoring to avoid bacteria. If you use a roof as your catchment area, you want to ensure that your water doesn't mix with heavy metals or lead, which could affect the water quality. Materials like aluminum and galvanized iron are the best for roofs used to harvest rainwater.   

Groundwater recharge 

groundwate recharge
Photo by Water Alternatives Photos on Flickr licensed under CC BY 2.0 (Cropped from original).

This type of system collects rainfall at ground level. It is more complex and requires constructing a storage tank, a pump, piping, and other distribution systems. 

A basin is placed at the bottom of a slope to capture rainwater that soaks the ground. The pump then retrieves and distributes the water. For irrigation and plumbing around your house, you may need to do some underground piping for proper distribution.   

Portable water system  

A portable water system is the most complex and is used to create drinkable water. This system includes a rainwater collection area, filtration, pumps, storage, treatment, additional piping, and a pump. 

These types of systems are more expensive and require high-quality filters and a great amount of maintenance to prevent low water quality, which could affect human health. However, the benefits of having a portable water system right in your home will give you access to free water and help you build self-sufficiency. This means you won’t need to rely on water supply from your city, helping you save costs. 

If you’re using portable water systems, you may want to involve professionals to ensure you’re building an adequate system that guarantees a safe water supply in your home. 

What is harvested rainwater used for?

Harvested rainwater is sustainable and a great way to reduce your environmental footprint. You can use your collected rainwater for a variety of uses: 

  • You can use your collected rainwater for indoor non-potable uses like toilet flushing and household chores like washing clothes and cleaning. 
  • You can collect rainfall water for watering plants and irrigation. 
  • You can use rainwater to refill your swimming pool or fountains.
  • You can use rainwater to wash your windows, patios, and decks.
  • Stored rainwater can be helpful if there’s a fire outbreak.
  • A more advanced harvesting system with proper filtration and pump can be used for drinking and cooking. This can be an excellent and sustainable alternative to tap water or bottled water
  • Rainwater can be beneficial for industrial processes like manufacturing and cooling. 

Benefits of rainwater harvesting systems

rainwater tank
Photo by Harry Cunningham on Unsplash.

Rainwater harvesting provides many benefits, from environmental to financial and practical benefits. Here are a few reasons why rainwater harvesting is great for you and the environment: 

  1. Reduces stormwater runoff: With a rainwater harvesting control system, you can reduce runoffs in urban locations, which leads to pollution and soil erosion.
  2. Reduce energy consumption: Treating and transporting municipal water can be energy intensive. But with rainfall water usage, you can save energy.
  3. Conserves natural resources: In some parts of the world, water is limited, with demand surpassing the supply available. Using harvested water helps to reduce demand for surface and groundwater water sources. It helps to protect natural water bodies like rivers and streams. 
  4. Saves cost: While the initial investment for a complex rainwater harvesting system may be expensive, it ultimately helps reduce utility costs in the long run.
  5. Free of contamination: Chemicals and pollutants are not present in rainwater, unlike municipal waters, which are great for plants.  
  6. Backup for emergencies: If there is a crisis or natural disaster, rainwater collection systems can provide access to water when in demand. 
  7. Flexible and scalable: You can set up a rainwater system in various environments, from residential to commercial areas.            
  8. Promotes sustainable practices: Implementing a rain collection system increases awareness about sustainable water management practices and encourages individuals and communities to adopt more eco-friendly solutions. 

How to create your own rainwater collection system

Creating your own rainwater collection system can be a beneficial experience that helps you conserve water and save money. It is a sustainable way to harvest and use rainwater for various purposes, including watering gardens, flushing toilets, and non-potable household uses. So here's how you can go about building your own stand-alone rainwater collection system: 

  1. Determine use: The first thing you want to do is determine what you will use rainwater for. Is it for irrigation, household chores, or perhaps drinking? This will help you choose a suitable collection method. You also want to consider the rainfall patterns in your location. 
  2. Pick a collection method: Your collection method will typically be your roof. Ensure that your roof, gutters, and downspouts are clean and debris-free. You may want to install gutter guards to reduce maintenance and prevent debris from clogging your gutters. 
  3. Install a first flush diverter: A flush diverter device ensures that rainfall that could be polluted from the roof doesn't go into your rain barrels or storage tanks.
  4. Attach downspouts: Adjust downspouts to move water into your storage tanks. If you're using multiple rain barrels and tanks, you could link them together. 
  5. Install filtration system: You also want to install a filtering system to remove contaminants and debris before water enters the storage containers. This is especially important if you're installing a system for indoor use. You also want to install a basic filter to improve water quality for outdoor use. 
  6. Connect an overflow system: To prevent water logging around your home, it is important to have an overflow system. For example, you can direct excess water to your garden and prevent waterlogging. 
  7. Position your tank: Place your tank or rain barrels in a suitable location for easy access and maintenance. Your storage tank should have a secure lid that removes debris and pests. 
  8. Install a pump: If you plan to use the water for irrigation or you simply want to distribute more water around your house, you can install a pump. 
  9. Install a water level indicator: You can install a water level indicator to help you monitor water usage from your tank. 
  10. Regularly clean your system: Ensure you clean your tank(s) and gutters and check for any leaks to ensure they last and work efficiently.
  11. Check for local regulations: Some locations may have regulations for rainwater harvesting. You want to stay informed about these regulations to ensure you comply with them. 

Wrapping up 

Collecting rainwater is a sustainable and cost-effective way to manage water. Using free water available by rainfall can reduce demand for municipal water supplies and contribute to a more sustainable future. 

Jen’s a passionate environmentalist and sustainability expert. With a science degree from Babcock University Jen loves applying her research skills to craft editorial that connects with our global changemaker and readership audiences centered around topics including zero waste, sustainability, climate change, and biodiversity.

Elsewhere Jen’s interests include the role that future technology and data have in helping us solve some of the planet’s biggest challenges.

Fact Checked By:
Isabela Sedano, BEng.

Photo by frame harirak on Unsplash.
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