Elements Of A Rainwater Harvesting System
First, let’s go over the parts of a typical RHS. Of course, not every system will have all these parts, but we should understand what each part does and how they all work together. This information will allow us to design an RHS that achieves our goals. Parts below will be noted as either ‘mandatory’ or ‘optional’.
If you see a term you don’t recognize, check the glossary at the end of the book. There are a lot of specialized terms that might take a bit of time to become familiar with, and most of the parts of an RHS can have a few different names.
Collection Area (Mandatory), also known as a catchment area or collection surface
This is the surface that rainwater lands on and is harvested from. For most residential rainwater systems, this will be the roof of your home.
Connects to: Transfer System
Pre-Filter (Optional), also known as pre-treatment Anything that removes debris or contamination from rainwater before it reaches the Storage Tank is considered pre-filtering. This is usually intended for physical contaminants and includes options like gutter guards and leaf filters.
Connects to: Transfer System
Transfer System (Mandatory), also known as a conveyance network or conveyance system
This is the system of gutters and pipes that moves the rainwater from the Collection Area to the Storage Tank. Some of this may already be present in your home, like the gutters on your roof, and some of it will need to be installed.
Connects to: Collection Area, Storage Tank
Storage Tank (Mandatory), also known as a basin, cistern, holding tank, water butt, or rain barrel
The Storage Tank holds the collected rainwater before it gets used. The Storage Tank is the central hub of the RHS. Everything comes into, sits in, or goes out of the Storage Tank.
Connects to: Transfer System, Connection System
Overflow (Mandatory), and Make-Up Systems (Optional)
A Storage Tank isn’t just an empty tank; it may have some controls in place for extreme situations. Too much water (solved by an Overflow system) or too little water (solved by a Make-up system) can cause severe problems in your RHS. These systems aren’t necessarily complex but have to be considered.
Connects to: Storage Tank
Pump (Optional)
Almost every system will have a pump unless the water is drained directly from an aboveground storage tank for nearby use. Pumps will sit inside, or near, the Storage Tank and usually require an electrical connection, but manual pumps are also an option. Additional pumps may be added after the Treatment System to reach fixtures further away or which are elevated above the Storage Tank.
Connects to: Storage tank
Connection System and Fixtures (Optional)
The Transfer System brings rainwater into your Storage Tank, and the Connection System moves that rainwater to where a fixture uses it. A fixture could be a tap, toilet, or appliance that uses rainwater.
Connects to: Storage tank
Treatment System (Optional), also known as post-treatment, filter, or disinfection
Most uses of rainwater will require some treatment, but there are a few cases where this isn’t necessary. The level of treatment needed will be based on the amount of contamination picked up from the Collection Area surface and the required water quality for your intended uses.
Connects to: Connection System
Sensors and Controls (Optional),
Depending on the complexity of your system, you may need to monitor what is happening inside the Storage Tank. The most common combinations are water level sensors combined with valves. The sensors and controls could be linked to the Overflow, Make-up, or Pump Systems. However, you might also need sensors and controls for other parts of your RHS.
Connects to: Storage Tank
Cold Weather Modifications (Optional)
Several modifications can be made for an RHS operating outdoors in temperatures below freezing. These are specific to each element of the RHS and will be covered in Step 2.
Connects to: Various elements
Common Rainwater Harvesting Questions
Here is a compilation of the most commonly asked questions about rainwater harvesting:
Q: Is rainwater safe to drink?
A: Yes. Rainwater isn’t pure but has much less contamination than most other sources, like groundwater or surface water. See ‘Rainwater Quality’ below for details.
Q: What skills do I need to install a rainwater system?
A: A basic rainwater harvesting system requires some basic plumbing skills, like being able to measure, cut, and fit pipes together. More complex designs will require some electrical work, engineering, and a basic understanding of water chemistry. However, many complex parts of an RHS, like Pumps or Treatment Systems, can be purchased as all-in-one packages that don’t require extensive knowledge, tools, or skills.
Q: Does rainwater harvesting cause environmental damage?
A: Harvesting rainwater does not permanently remove water from the local environment. Instead, an RHS can help conserve local groundwater aquifers and slow down the effects of erosion from surface runoff.
Q: Is rainwater harvesting legal?
A: Rainwater harvesting itself is legal, but there may be restrictions or limitations on how you can use that water or how much you can collect. That will be covered in Step 1: Pre-planning but will require some additional research and double-checking based on your local laws and regulations.
Rainwater Quality
Rainwater is nearly pure while it’s in the air, but as soon as it hits a surface, there is a chance for it to become contaminated.
Water quality is essential if you plan to use your harvested rainwater as drinking water. But you will still want to maintain a high standard of water quality for other uses as well.
Contamination picked up from the Collection Area can make rainwater unsuitable for drinking, watering gardens, or other household uses. There are three types of contamination to worry about: physical, chemical, and biological. These can all affect rainwater’s taste, color, odor, and safety. These are discussed in detail in the section in Step 2 on Treatment Systems.
The best approach to maintaining the highest level of water quality is to use a multi-barrier approach. This approach is the gold standard used by any largescale drinking water system. So while your RHS will be much smaller, the same principles can also benefit you. Using multiple methods to reduce contamination and keep rainwater clean through every step of the harvesting process ensures that we aren’t relying on any single approach or piece of equipment to protect us. If one part of the Treatment System is not performing well, you will still receive high-quality water.
The RHS design will incorporate a multi-barrier approach, and we will cover the details of water quality and treatment later On our website.
