Safe for Harvesting

Feb. 3, 2017
Rainwater harvesting standards ensure safety for potable water applications

About the author: Jason Carlson is staff chemist and technical lead for potable water system product certification for UL LLC. Carlson can be reached at [email protected].

If you manufacture roofing materials, coatings, water distribution and containment products, or even solar panels, you may have been asked the following question: Is it safe to use your company’s product for a rainwater harvesting system?

Above: Table 1. Rainwater Harvesting Standard Requirements

If you have not heard this question yet, it is likely you will in the coming years. Rainwater harvesting is making a resurgence aided by increased sustainability awareness and new green building practices. Green building rating systems, such as LEED, even award points for water conservation measures like rainwater harvesting.

Methods for collecting rainwater have been employed successfully by our ancestors for thousands of years without the benefit of modern science, materials or technology. To summarize the process, a large impermeable surface, such as a roof, initially “catches” rainwater. The water then is diverted from the catchment surface by gravity and a network of gutters, pipe or tubing, eventually leading to a protected tank or cistern. This stored freshwater can be used over time, as needed, for either potable or non-potable needs. With as little as 1 in. of rainfall on a 2,000-sq-ft roof, 1,250 gal of water can be harvested. For most locations in the U.S. and Canada, tens of thousands of gallons of freshwater can be harvested by a typical single-family residence annually.

Benefits of harvesting rainwater include the following:

  • Cost-effectiveness: Rain is free, meaning the only costs are in the construction of a catchment system.
  • Decreased utility bills: Rainwater harvesting reduces storm water runoff and demand on existing water utilities and can help lower consumer utility bills.
  • Usable at the source: Large-scale and costly distribution system are not necessary.
  • On-demand availability: Once stored, harvested rainwater can provide freshwater when other sources, including groundwater, are unavailable.
  • Purity: Rainwater starts pure, with little or no dissolved minerals or chemical contaminants.

Common questions about rainwater harvesting include:

  • Are there regulations in place for the construction of rainwater catchment systems and the usage of the water they collect?
  • How is the quality of the collected water ensured, especially if intended for potable use?

It is best to check with state and local governments to see which restrictions are in place and which codes must be followed. Many cities and states now have guidance on the construction of rainwater catchment systems available online. Other helpful resources are available from organizations like the American Rainwater Catchment Systems Assn. (ARCSA).

Rainwater Harvesting Standards

In 2013, ARCSA and the American Society of Plumbing Engineers (ASPE) published the first Plumbing Engineering and Design Standard for Rainwater Catchment Systems, titled ARCSA/ASPE 63-2013. The standard provides guidance on creating and maintaining a safe alternative to municipal or well water sources by reducing consumer risk from poor design, installation and maintenance of rainwater collection systems.

In 2015, the Uniform Plumbing Code (UPC) added requirements for rainwater harvesting systems. When harvesting for potable use, all distribution materials must meet the existing potable water supply requirements of the code.

The Canadian Standards Assn. (CSA) and the International Code Council (ICC) also partnered to form the Rainwater Collection System Design and Installation Standard Development Committee. Currently in draft format, CSA/ICC 805-201x would become a similar standard for the design, installation and maintenance of rainwater collection systems intended to collect, store, treat, distribute and use rainwater for potable and non-potable applications.

Rainwater harvesting system design standards, along with the UPC, stress the importance of components evaluated to NSF standards when harvesting potable water. Table 1 shows the current requirements of NSF P151: Certification of Rainwater Catchment System Components and NSF/ANSI Standard 61: Drinking Water System Components – Health Effects.

Potable Applications

When it comes to using rainwater for potable applications, there are additional precautions to keep in mind. Although rainwater can be pure, organic debris such as branches, insects and bird waste can end up on a rooftop. Stored water intended for human consumption requires additional processing to ensure it is safe to drink. Proper filtration and purification are still required. In addition to contamination from outside the system, all components and materials in contact with rainwater intended for potable end use should comply with NSF P151 and/or NSF/ANSI 61. Compliance ensures harmful levels of chemical contaminants are not extracting from a catchment system into the water supply.

Certification to NSF standards is granted by an accredited third-party testing laboratory if a product, component or material meets the applicable standard requirements.

By demonstrating compliance to the appropriate NSF standards, you can put a customer’s or official’s mind at ease. 

About the Author

Jason Carlson

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