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?” If so, did you know how to respond to the customer or official?

If you haven’t 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 harvesting rainwater.

Methods for collecting rainwater have been successfully employed 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, would initially “catch” rainwater. The water would then be diverted away from the catchment surface by gravity and a network of gutters, pipes, or tubing eventually leading to a protected tank or cistern. This stored freshwater could be used over time, as needed, for either potable or non-potable needs. With as little as 1” of rainfall on a 2,000 ft2 roof, 1,250 gallons of water can be harvested. For most locations in the US and Canada, tens of thousands of gallons of freshwater can be harvested by a typical single-family residence annually.

Benefits of harvesting rainwater:

  • Cost Effective – Rain is free, meaning the only costs are in the construction of a catchment system.
  • Decreased Utility Bills – Rainwater harvesting helps reduce stormwater runoff and demand on existing water utilities and can help drop consumer utility bills.
  • Used at the source – Large scale and costly distribution system are not necessary.
  • On Demand – Once stored, harvested rainwater provides freshwater when other sources, including groundwater, are unavailable to the user.
  • Purity – Rainwater starts pure, with little or no dissolved minerals or harmful chemical contaminants.

Common questions:

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 the state and local governments to see if any restrictions are in place and what 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 such as such as The American Rainwater Catchment Systems Association (ARCSA.org).

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 objective of the standard is to provide guidance on creating and maintaining a safe alternative to utility 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.

In addition to the published 2015 UPC and ARCSA/ASPE 63-2013 standards, the Canadian Standards Association (CSA) and the International Code Council (ICC) 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. Below is a table which shows current requirements regarding NSF P151 and NSF 61.

When it comes to potable water there are additional precautions to keep in mind. Although rainwater can be quite pure, organic debris such as branches, leaves, pine needles, insects, and even bird waste can end up on a rooftop. Stored water that is intended for human consumption will require additional processing in order to help ensure the water will be safe to drink. Proper water filtration and purification is 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 (National Sanitation Foundation) standards P151 and/or 61. Compliance helps ensure that harmful levels of chemical contaminants are not extracting from a catchment system into the water supply.

How to help ensure compliance to the applicable NSF standards:

Certification to NSF standards would be granted by an accredited 3rd party testing laboratory, such as UL, if a product, component or material meets the applicable standard requirements.

This takes us back to the original question, “Is it safe to use your company’s product for a rainwater harvesting system?” By demonstrating compliance to the appropriate NSF standard you can put that customer or official’s mind at ease.


Jason Carlson is a staff chemist and technical lead for potable water system product certification at UL LLC, where he has worked for the past 8 years. Jason is a graduate of Purdue University, West Lafayette, IN and currently resides in Oregon. He can be reached at jason.carlson@ul.com or 847.664.3179.

As originally published in the February 2017 issue of WQP Magazine.