Active Rainwater Harvesting Systems: Essential Features

From simple rain barrels to elaborate installations with millions of gallons of storage, the rules of rainwater harvesting are more or less the same. Components may vary in size and capacity, but in any implementation, the following features are required:


First, a catchment surface is needed. For rainwater harvesting, this is most frequently a roof because roofs tend to deliver the cleanest, highest quality water when compared with other potential catchment surfaces like patios, driveways, parking lots or other landscape features that shed water.


Next, water must be conveyed from the point where it runs off of the catchment surface to where it will be stored. Components of the conveyance system can include household gutters, downspouts and other piping. Conveyance may be above ground or below depending on site attributes and client requirements but must be appropriately sized and sloped to handle peak water flows that may occur during intense storm events.

pre-storage filtration

Prior to being directed to storage, rainwater must be filtered. It is critical to ensure that the water entering any tank, cistern or rain barrel is as clean as possible. This helps to avoid future problems and reduce system maintenance.

Secure connections

From gutter to tank, all interfaces between system components must be secure to prevent infiltration from debris, insects and other unwanted pests.


Rainwater can be stored in many types of tanks and cisterns both above and below ground. Common materials include concrete, steel, fiberglass and plastic. The size of storage you need is a function of your local rainfall patterns, the size of your catchment surface and your demand for water. We can help to ensure that your tank is appropriately sized for your specific needs.


Consideration of overflow is critical. In most locations in coastal BC, we have enough seasonal rainfall to fill even large cisterns many times over. Overflow can be connected to installed drainage systems, but we encourage clients to think of other possible uses for their system overflow. These could include a pond, rain garden or other infiltration method.

post-storage Treatment

For non-potable uses, elaborate post-storage treatment is usually not required. If rainwater is intended for potable use, a treatment system must be installed. 


The distribution system gets rainwater from your storage facility to the location you want to use it in. It can be as simple as a nozzle at the bottom of the tank or may include a pump to give you more flexibility in how you use and deliver your water.