Rainwater harvesting is one of the most approachable DIY projects a homeowner can pursue and its potential positive impact is undeniable. It’s sustainable, cost-effective, and simple to install. Nevertheless, an understanding of how a system works and the various parts will go a long way to helping you install a useful and maintainable setup.
The five components of rainwater harvesting are:
- A catchment area
- A conveyance system
- A storage system
- A distribution system
- A filtration system
Here we’ll go through each of these components in depth and the things you should consider when planning to build a collecting system.
The catchment area is the surface that rainwater falls onto and is the component that will dictate how much rainwater you can collect. The larger your catchment area, the more rainwater you’ll be able to collect. For most people, the obvious solution is their roof, as it’s large, easily accessible, and most homeowners have one. However, it’s entirely possible to collect rainwater without a roof.
However, it’s critically important to keep the catchment area clean. Debris such as twigs, branches, and leaves can clog up your conveyance system and prevent water from flowing into your barrels or cistern. Not only are you collecting less water because of these blockages, but there’s also a much higher likelihood of contaminating your water. There will be plenty of ways each component can introduce contaminants to your system, don’t let your catchment area be the first. Despite being the largest surface area (most likely) in your entire system, it’s also going to be the easiest to access and clean in most instances.
The conveyance component does what’s in the name: convey. It is the part of the system that moves water from the catchment area to the storage or distribution system. If you have a rooftop rainwater harvesting system, then this will be your gutters and your downspout. No matter what though, you’re going to capture rainwater with a large surface area (your catchment) and you’ll need some way to ‘convey’ that water into your storage system.
Because the conveyance system is responsible for moving the water from the catchment area to the storage system, it’s critically important to prevent and remove blockages that would prevent your rainwater from reaching the storage system. Even worse, this debris can introduce contaminants to the water that does make it to your storage system that may encourage algae or other aquatic plants to grow.
The conveyance system is the perfect point in a harvesting setup to screen or filter debris before it enters the storage system. This can be done by installing devices such as leaf guards or screens that prevent debris from entering gutters and downspouts in the first place. Additionally, a filtration system can be integrated into the conveyance system to remove any impurities before the water is directed to the storage system. This can include devices such as sand filters, UV filters, or reverse osmosis systems, which can remove dirt, sediment, and other contaminants from the water. By incorporating these types of safeguards your collected rainwater will be of higher quality and safer to use.
A storage system is the most important, and most obvious, part of a rainwater harvesting system. In order to save the water for later use, you’re going to need to store it and this is where rain barrels or cisterns come in. Barrels are typically used for smaller applications but can still hold a substantial capacity, especially when you connect multiple barrels together. Cisterns, on the other hand, are larger tanks for a much-increased storage capacity and make more sense when rainwater is a primary source of water in your household.
When planning your storage system, the capacity of your storage receptacles is an important consideration. You should know roughly how much rainwater you can collect with your catchment area ahead of time so you can prepare the right amount of capacity. You can do this with our roof rainwater calculator here. You’ll also want to think about how fast you’ll use the water. The calculator will give you a rather big number for the year but, if you’re using the water as you capture it, you may not need a storage unit large enough to hold a year’s supply.
While the greatest risk of a conveyance is debris, leaves, and blockages, barrels and cisterns are susceptible to contaminants and mosquito larvae. If the water supply isn’t maintained, and the wrong contaminants or debris get into the barrel from your catchment surface, algae can bloom, mosquitos may lay eggs, or the water may become otherwise unusable. It’s important to regularly check the pH and for chemical contaminants and address issues immediately, especially if you are drinking your rainwater.
You can check out what to look for in a rain barrel in our guide here which covers all the aspects of a rain barrel you may want to consider.
You’ve gone through all this effort to capture and collect rainwater. You want to use it! You’ll need to distribute it from your rain barrels to the location where you plan on using it and for this, there are two typical types of systems: Gravity-fed systems and pump-fed systems.
Gravity-fed systems rely on, well, gravity to get the water to where you need it. These systems typically consist of a series of pipes that are connected to the storage system and run to the point of use, such as a garden or irrigation system. The pipes are usually buried underground, and the water flows through them by gravity. This type of system is relatively simple and inexpensive to install, but it requires a certain elevation difference between the storage system and the point of use to work efficiently and develop enough pressure. You will need a lot of height to get the pressure you might be expecting though.
Pump-based systems use a pump and in most cases, we highly recommend going with a pump. The pump pressurizes the water and moves it through pipes or hoses with sufficient pressure. While it’s slightly more expensive and more complex to install, the flexibility that it allows for the location, and distribution, of your rainwater harvesting system is well worth
Finally, the filtration system is an essential component in a rainwater harvesting setup. Depending on how you plan to use the water, the quality and potability of the collected water can be addressed with filters. Without a filtration system, the water may contain harmful microorganisms and contaminants that can cause illness or damage to appliances.
The filtration system can sit in a number of places within your system but it is typically integrated into the conveyance system, immediately before the water reaches the storage system. It is occasionally placed between the storage and the distribution component. You can learn about the various types of filters that might be right for you in our guide here.