Basics of Rainwater Harvesting
Harvesting rainwater involves the utilization of some sort of collection system of rainwater for various uses including plumbing, and/or irrigation and various other outdoor and non-potable indoor uses.
The Environmental Protection Agency (EPA) in its Municipal Handbook, Managing Wet Weather with Green Infrastructure, that considers rainwater harvesting policies, states that rainwater harvesting also reduces runoff of stormwater and therefore pollution, and reduces soil erosion in urban environments.
As an increasing number of U.S. states have been affected by drought, there has been more focus on harvesting rainwater for consumption. As the EPA document points out, rainwater can:
- Provide an inexpensive supply of water
- Augment supplies of drinking water
- Help with demand management for drinking water systems
Typically, rainwater harvesting systems divert runoff from both residential and commercial roofs and store it. It is then piped or channeled to where it can be used.
However, neither the International Plumbing Code (IPC), adopted with amendments by New York State (NYS), nor the Uniform Plumbing Code (UPC), developed by the International Association of Plumbing and Mechanical Officials (IAPMO), address rainwater harvesting in their stormwater or potable water sections. The codes do though cover water for reuse.
The UPC definitions of water for reuse are:
- Graywater, which is defined as untreated wastewater that hasn’t had contact with sewage (black water). This includes water from showers, bathtubs, lavatories, and washing machines used for clothing.
- Reclaimed waterthat has been treated by a public agency to wastewater tertiary standards and is suitable for controlled use. Conveyed in purple pipes, reclaimed water is commonly used for water supply to water closets, urinals, and for trap seal primers that are designed for floor sinks and drains.
- Harvested rainwater, which is stormwater conveyed from the roof of buildings that is stored in a cistern (or tank) and disinfected and filtered before it is used for toilet flushing. The UPC also states that it can be used for landscape irrigation, but does not list the other possible uses mentioned above.
In spite of the codes, until very recently when the new Rainwater Harvesting System was introduced, there was considerable confusion relating to the reuse of water. Also, state legislation differs, with some U.S. states being more restrictive in terms of how rainwater is used, and some in terms of using rainwater at all. In Colorado, for instance, water rights laws are interpreted as prohibiting rainwater harvesting because cisterns and barrels prevent rainwater runoff from reaching the state’s rivers. This, in turn, decreases downstream users’ allotted water rights, so rainwater capture and reuse are simply prohibited!
At the same time, some states have incentives that encourage rainwater harvesting. For instance, the New York State Senate has introduced a tax bill that plans to offer credits to homeowners and businesses that invest in green infrastructure that manages “wet weather impacts” that provide many community benefits. This includes reducing and treating stormwater at its source rather than utilizing the conventional gray stormwater infrastructure that moves urban stormwater away from the built environment – including our homes. Other initiatives that will likely be rewarded include rain-gardens, green roofs, and permeable pavements.