It doesn’t take much to successfully harvest rainwater that is suitable for use around a home or property to water the landscape. At its most simple, all that’s needed for rainwater harvesting is a good surface to catch rain from, a container, and a means to channel rainwater to that container. But by adding a few products, pieces of equipment, and accessories to the rainwater system, you can greatly improve the quality of harvested rainwater, reduce the amount of regular maintenance, and even increase the number of applications the rainwater can be used for.
In rainwater harvesting, the best practice is to collect rainwater while not collecting debris that can get washed off from whatever surface the rain is being harvested from. In this Rain Tanks Series post, we will provide a brief overview of the components recommended for a successful rainwater harvesting system.
Rainwater Harvesting System Overview
In short, the components of a successful rainwater harvesting system will include a rain catchment surface, a conveyance system, a downspout screen leaf eater, a first flush diverter, a tank screen, a collection container, overflow, bulkhead fitting, and a way to connect to the bulkhead to withdraw rainwater. Additional components may include a solar shield, tank screen cover, water pump, and/or a water treatment system.
At first, this may sound like a lot of required or recommended components, but most catchment surfaces (e.g., roofs) include a conveyance system, (e.g., gutters, downspouts, piping), or one that can be easily modified. Also, most rainwater collection containers come standard with a tank screen, overflow, and bulkhead fitting. This leaves a downspout screen, a first flush, a means to withdraw rainwater, such as a hose, water pump, or spigot, and any additional components, such as a water treatment system, to be added as needed.
The following sections of this post will consider the overall rainwater harvesting path, equipment, their install location and function. We will look into this in more detail for a better, overall insight into the components of a successful rainwater harvesting system.
From Clouds to Harvest
To provide a layout of rainwater harvesting components, their function and placement, we will first consider the general path all rainfall takes from the clouds to harvest to use.
Rain (a) falls from the sky as precipitation, (b) lands on a catchment surface, (c) flows from the surface to a conveyance system that (d) directs the rainwater to a collection container where (e) the water can be stored until withdrawn for use. As the rainwater is withdrawn for use it may then travel through pipes, hoses, or be simply released from a spigot valve into a watering can.
As rain falls, the water can pick up dirt, dust, and any potential chemical gasses in the air. As the rain falls on a catchment surface, the water will rinse the surface and can pick up debris such as sticks, leaves, other plant matter, moss, mold, parts of dead animals and insects, and can wash up material that dissolves in water such as animal feces, sediment, or chemicals that may be on the catchment surface.
By this point in the rainwater harvesting path, rainwater can be fairly dirty and/or contaminated to a point unfit for drinking.
Here, we are using the term “dirty” to mean rainwater with unwanted debris and “contaminated” to mean rainwater with bacteria that could make you sick if drank. Dirty rainwater is simply undesirable and perhaps visually unpleasant, can cause clogs and lead to odors as debris begins to decompose over time. Contaminated rainwater is primarily the result of animal droppings and typically only a concern if the water is to be used as a potable water source and consumed in some way. For more on this, see our Rain Tanks Series | Why Should I Not Drink Rainwater (Before Treating It)?
From the catchment surface, the rainwater will flow through a conveyance system and to the collection container for storage. From storage, the rainwater can be withdrawn from a bulkhead fitting outlet using any compatible hose, pipe, valve, or adapter.
From Catchment to Conveyance
In the catchment area to conveyance system part of the rainwater harvesting path, there are not any additional components that can be added to improve the quality of water collected. However, it is at this point of the rainwater path that the water becomes the dirtiest and should be cleaned.
Cleaning the rainwater, removing debris, and improving the catchment area will provide better quality rainwater for applications and reduce the amount of regular maintenance the overall system will require.
Options to improve the catchment area include: (1) use a preferred catchment area material type such as metal, (2) have the catchment area cleaned regularly of growing moss, (3) keep gutters clean of debris, and (4) ensure gutters are properly installed to prevent standing water and water loss.
From Conveyance to Collection
Between the conveyance system and the collection container is the main location to add accessories to clean out debris and some potential contaminants while harvesting rainwater. From conveyance to collection is the space from the roof to the rain tank and refers to gutters, downspouts or pipes. Rainwater harvesting components that can be installed and added on at this section include gutter guards, downspout screens, and first flush diverters.
- Gutter guards can be installed over the gutters as a measure to keep larger debris such as leaves and sticks out of the gutters and conveyance system. This will reduce the amount of cleaning the gutters will need as well as the number of debris that makes it further downstream.
- Downspout screens, also known as leaf eaters or rain heads, can be installed in downspouts to catch and remove larger debris as rain travels from the roof, through conveyance to the collection container. The leaf eater is highly effective in providing a cleaner rainwater harvest. A downspout screen may require regular cleaning to remove accumulated debris to ensure rainwater can continue to flow through; however, this is an easy task and lightweight maintenance.
- First flush diverters, also known as roof washers, are best installed after a downspout screen, and are made to collect a set volume of the first rainfall and discard it rather than allow it to be collected at the rain container. The first rainfall is often the dirtiest as it is this initial rainwater that washes the catchment surface. After the initial washing, the catchment surface is often much cleaner, and the following rainwater is also often much cleaner.
At Collection Point
In rainwater harvesting practice, the collection point is the container used to store and distribute rainwater that has been successfully harvested. Common collection point containers include rain barrels, poly rain tanks, underground cisterns, IBC totes, and steel rain tanks. Rainwater harvesting components that can be installed at this section include a tank screen, a tank screen cover, a solar shield, and a water level gauge.
- The tank screen serves as a final line of defense against larger debris entering the rain container. The tank screen is a fine mesh filter basket that installs in the rain container manway and will catch debris that may have been missed or made it past the downspout screen or first flush.
- A tank screen cover installs as a lid over the tank screen accessory and keeps sunlight from reaching the water within the tank and therefore helps to prevent algae growth. The tank screen cover features preset port holes that allow for plumbing connections and rainwater inflow.
- A solar shield functions as both a flow calming device and sun-blocker. The solar shield installs at the manway beneath the tank screen inside the tank where it blocks sunlight and brakes incoming rainwater, slowing it down and preventing resuspension of sediments within the tank. A solar shield is ideal for systems without a tank screen cover and can also be used with one to calm flow.
- A water level gauge installs directly on the rain tank and allows current rainwater volumes within the tank to be easily seen and monitored without having to open the tank for inspection. Most rainwater tank gauges are mechanical and do not require electricity.
From Collection Container to Use
From the collection container to your rainwater application and use, the necessary components for successful practice include the overflow and the bulkhead fitting. At this point in the rainwater harvesting path, the collected rainwater should be free (or mostly free) of debris. All that remains should be dissolved contaminants from chemicals, animal droppings, and sediment from dirt, dust, and pollen that are too fine (i.e., small) to be removed by mesh screens and that may have made it past the first flush diverter.
The Overflow
The overflow installs near the top of a rain container and serves as an outlet for excess rainwater to drain from the container whenever it becomes full. The proper setup for a rain tank overflow will use additional plumbing, such as PVC pipe or a hose, to discharge excess rainwater at a location and direction away from the base of the rain container and away from any other structure or foundation. An overflow can also be used to connect multiple rain tanks together. Without an overflow, excess rainwater will spill out of the manway and over the container.
Many commercially available rainwater collection tanks include an overflow kit. For rainwater collection containers without a pre-installed overflow, an overflow outlet kit can be purchased and is fairly easy to install.
Rainwater from an overflow can also be put to good use. Rather than simply being discarded to the ground or a storm drain, an overflow can be setup to release the extra water to a nearby landscape or garden. This is what the owner of the rainwater tank did in the example picture at the beginning of this post. In that picture, the overflow (at the top of the tank) has been modified to fit a garden hose and the hose is directed to the nearby garden.
Tank Bulkhead Fittings
Rain tanks often include either one or two bulkhead fittings, and more can be installed as needed. Bulkhead fittings serve as either an outlet for withdrawing rainwater from the container or as an inlet for filling the tank. The bulkhead fitting outlet installed near the base of the tank can be used to make plumbing connections such as to a garden hose or PVC pipe to a water pump. The bulkhead fitting inlet is installed near the top of a rain tank and can be directly connected to the conveyance system for rainwater inflow. Bulkhead fittings can also be used to connect multiple rain tanks together and increase the overall volume capacity of the rainwater harvesting system.
Additional Rainwater Components
Additional components that may be included in a rainwater harvesting system include a water pump and a water treatment system. These will be installed between the collection container and the point of use.
- A water pump is only needed in rainwater harvesting whenever increased water flow rates (GPM) and increased water pressures (PSI) are required by the application. Example rainwater uses that require a water pump include sprinklers, irrigation systems, spray nozzles, and indoor uses. A water pump is installed between the collection container and the plumbing system that is used to distribute the rainwater. Most often, PVC pipe is used to make these connections.
- A water pump is only needed in rainwater harvesting whenever increased water flow rates (GPM) and increased water pressures (PSI) are required by the application. Example rainwater uses that require a water pump include sprinklers, irrigation systems, spray nozzles, and indoor uses. A water pump is installed between the collection container and the plumbing system that is used to distribute the rainwater. Most often, PVC pipe is used to make these connections.
- A water treatment system for harvested rainwater will only be necessary for select applications, such as potable (drinking) water uses, indoor non-potable uses, and outdoor applications that require clean, sediment-free water, (e.g., irrigation system). Many different water treatment systems exist. Our top recommendation for a rainwater treatment system is a multistage cartridge filter with ultraviolet (UV) light chamber. For clean, sediment-free water, a cartridge filter unit may be sufficient.
Water treatment systems require higher pressures to operate and are installed after a water pump and before the use. For rainwater harvesting setups using a treatment system, oftentimes a secondary tank, such as a pressure tank, is included in the setup to store treated water for on-demand supply.
Takeaway | Components of a Successful Rainwater Harvesting System
Rain will often become dirty and collect debris as it falls from the sky, lands on a surface, and flows to a point where the rainwater will be stored for use. Along this rainwater harvesting path, various components are necessary to successfully practice rainwater harvesting and various other accessories can be added to increase the system’s overall effectiveness and cleanliness. Necessary components are the catchment surface, conveyance system such as gutters and downspouts, and the collection tank with bulkhead fitting. Additional components include mesh filter screens such as tank screens and leaf heads, a first flush diverter, tank overflow, and more.
If you are looking to harvest the rain, we provide the rain harvesting accessories necessary for a basic setup as well as some water treatment units for a complete potable grade water system. We also provide ANSI/NSF 61 certified rainwater tanks in poly up to 10,000 gallons and galvanized steel rain tanks up to 100,000 gallons. Contact our support staff for questions, inquiries, or assistance in implementing your very own, successful rainwater harvesting system.
