Rainwater Harvesting

Not Your Daddy’s Rain Barrel: A New Rain Tank Design Specification

Archaeologists tell us that rain tanks and cisterns have been around since the bronze age. They are still a major part of urban infrastructure in Europe, Australia, New Zealand, India and the Caribbean. But try finding them in the Bay watershed, or in any state stormwater design manual. Despite their prime advantage of using stormwater as a resource rather than something to be disposed of, they are currently not much of a weapon in our Bay stormwater arsenal.

Part of the reason has been the lack of a design specification for rain tanks. CSN, in partnership with several rainwater harvesting experts, has filled this gap, by releasing a rain tank specification. This new specification is different in that it seeks to optimize the total amount of runoff reduction from the roof, through internal water use, outdoor irrigation and detention/release of rainwater into secondary runoff reduction practices. A slideshow, developed by CSN, provides more visuals on the new rain tank concept.

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So forget the notion of a rain barrel… the new spec introduces a much more sophisticated design that integrates the plumbing of the roof with the plumbing of both the building interior and the landscape or yard. The tank is hardwired into the architecture of the building, and is a sustainable source of non-potable water. The beauty of the new approach is that homeowners understand that they need to maintain plumbing when it goes wrong.

CSN continues to invite thoughts on two specific areas. The first area is what, if any, local codes need to be changed in your community to permit the use of non-potable water. The second area relates to how rain tanks can be integrated into the construction of new residential and commercial buildings. Clearly, architects and green building folks need to think through how tanks can best promote the function and appearance of the building.