Rainwater harvesting is a process that captures, stores and reuses rainfall water. It is typically used for non-potable purposes, such as irrigation, flushing toilets and cleaning, but it can also be used for drinking water if properly treated. Harvesting and reusing rainwater can be a cost-effective and energy-efficient sustainability measure, reducing a building’s use of municipal potable water without inconvenience to its occupants
Commercial properties, such as shopping centers and office buildings, can benefit from rainwater harvesting because a large percentage of the water used is not for drinking.
According to a study from the National Resources Defense Council, up to 80 percent of potable water used in residential buildings may not require drinkable water. For commercial buildings, this percentage may be even higher because contact uses (such as showering and cooking) are lower. An estimated 25 percent of drinking water delivered to commercial buildings is flushed down the toilet.
How Rainwater Harvesting Works
The basic components of a rainwater harvesting system are:
- Catchment area (generally a roof), commonly made from galvanized metal, concrete, tile or slate
- Gutters and downspouts to transfer water from the catchment area to the tank
- Storage tank, located above or below ground
- Delivery system to channel the water to its end use
- Treatment or purification system if the water is intended for drinking
A variety of factors can affect how efficient the rainwater harvesting system is, including the amount of rainfall, the tank volume, the catchment area and the water demand.
The Benefits of Rainwater Harvesting
Harvesting and reusing rainwater provides many benefits for commercial properties:
- A system can be customized to a building’s needs, ranging from a small storage tank used for watering plants, to a large tank used for flushing toilets, laundry and cleaning machinery.
- An on-site water supply can be used for non-potable purposes with little or no treatment.
- Groundwater resources have been declining in the U.S., and the cost of water is rising. Rainwater harvesting can reduce water bills for commercial properties. It also diminishes the strain on the municipal potable water supply, as well as the economic and energy costs of treating and delivering potable water for non-potable uses.
- Harvesting can reduce stormwater runoff, which overloads storm sewers and lead to erosion or flooding.
Commercial buildings – whether they are new constructions or existing properties undergoing retrofitting for better efficiency – stand to benefit from rainwater harvesting systems.
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