Rainwater Harvesting for Homeowners

— Written By and last updated by Elisabeth Purser
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Although rainwater harvesting has been practiced for thousands of years, recent concerns over water supplies and the environment have prompted a renewed interest in this method of water sourcing. While advanced systems are commercially available, a homeowner can construct a simple rainwater harvesting system for home use with a basic understanding of its components and function.

A prolonged drought in North Carolina in 2007 and 2008 that necessitated mandatory water restrictions got consumers’ attention. Residents started thinking more about the options for alternative water sources. Most homeowners use potable water (treated drinking water) to satisfy all of their water needs, but this type of water can be replaced by captured rainwater for many purposes. For example, harvested rainwater can be used for watering gardens, washing vehicles, and flushing toilets. With special treatment and plumbing, it is even possible for harvested rainwater to become the primary water supply for a home or business.

A rainwater harvesting system captures stormwater runoff, usually from a rooftop, and stores that water for later use. Using harvested rainwater for purposes that don’t require treated drinking water has many advantages:

  • It reduces the demand on municipal water supplies and thus increases the sustainability of drinking water supplies.
  • Its use may be exempt from restrictions during a drought.
  • It can reduce water bills, meaning the system can partially pay for itself.
  • It can improve the environment by capturing nutrients and other pollutants from rooftop runoff, preventing them from contaminating surface waters.
  • It can contribute valuable plant nutrients, such as nitrogen and phosphorus, to garden irrigation water.

A rainwater harvesting system consists of four main components.

  • The cistern — or water storage tank — stores runoff for later use.
  • The gutter system collects runoff from the rooftop and directs it into the cistern.
  • The overflow pipe allows excess runoff to leave the cistern in a controlled manner.
  • The outlet pipe, which is sometimes connected to a pump, draws water from the bottom of the cistern for use.

Consider all of these components and how they work together before installing a rainwater harvesting system. The cistern is the primary component, so select and locate it based on anticipated water needs. Remember that local plumbing codes might affect the installation, and periodic maintenance will be required.

Cistern Selection

Woman in Pink Shirt and White Pants holding a water pot standing near a black rain barrelMany online retailers sell tanks that can be used for rainwater harvesting. Some companies focus specifically on rainwater harvesting systems. Homeowners can also find water tanks at local stores that sell agricultural, lawn and garden, or industrial supplies. For most systems, the cistern will have to be ordered and shipped directly to the location where it will be installed. Due to the large size and weight of many cisterns, delivery charges can be substantial. Select a cistern based on its material, size, whether it will be installed aboveground or underground, and where it will be located.

Rain Barrels

Rain barrels are less expensive alternatives to large rainwater harvesting systems and can be used to meet small outdoor water demands. A rain barrel is typically constructed from a 55-gallon container and has the same main components as a large rainwater harvesting system, including a gutter connection, overflow, and outlet valve or faucet. Because 55-gallon barrels are used to store and transport a variety of materials, used barrels are inexpensive to obtain. But they may require special cleaning, depending on their previous use. The relatively small size of a rain barrel usually does not merit the cost of installing a pump because gravity flow is generally adequate to fill a watering can. Although a rain barrel does not provide enough water to irrigate a lawn, it can be used to store water for hand-watering plants in a small garden area.