March 06, 2012

Rainwater Harvesting at the Castaway House

by: Cavin Costello


Today’s post is by Cavin Costello, the designer of the Castaway House:

The Castaway house is nearing completion and the central focus of the design, the landscape, is currently being installed. Jeremy Stapleton of Synergy Design Lab worked in collaboration with us from the very beginning to create a design that focused on desert indoor/outdoor living. The result was a beautiful and functional landscape design, which Jeremy describes as an “Edible, Medicinal, Sensory & Wildlife Garden.” This garden expands the interior of the house into nature and its neighborhood; all while being water efficient.

There are numerous active and passive systems involved in the design of the landscape to maximize the little water we receive here and it starts with harvesting. The site is designed and graded to drain into 6” recessed planting beds that are zoned by varying water demands to harvest site rainwater and keep it from wasting into the city sewers. All the rainwater from the roof is collected into 2, 600 gallon tanks. These tanks are then hooked up to an irrigation system that is controlled by an Evapotranspiration based irrigation controller with a rain sensor that corrects for site conditions. This low-volume system uses the stored rainwater, when available, to irrigate the plants through drip emitters.

The question you might be wondering now is how much rain can you harvest off your roof with the minimal 7” a year we get here. The Castaway House is 1970 square feet but its roof area, because of overhangs and its carport, totals 2907 square feet of catchment area. Over one year, the rainwater harvesting system will limit the use of city water in the landscape at the Castaway House by an estimated 13,513 gallons. All we can do once the system is hooked up is a little dance and wait for some rain.

Photo credit: All photos by the author.

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5 Responses

  1. KD says:

    This rain capture system, how much is it to install? Is it viable to do this to existing homes, or is it more feasible in new construction?

    • Taz Loomans says:

      Hi KD, I’m going to forward your question to Claire Aton, the project manager of the Castaway House and get back with you.

  2. KD,

    To answer your section question, it is definitely viable to do it to existing homes. Very minimal work needs to be done to the house itself in the installation of a rain capture system. Gutters need to be installed, some electric needs to be provided, and a water line needs to be run to the tank.

    As for cost, that is a very difficult question to answer since there are so many variables such as the amount of gutters, the size of the tanks, the type of operation of the tank, the existing connection points, and how the collected water will be fed to the landscape.

    If you want to see how these tanks work in person, come to the Castaway Open House, March 30th between 4-7pm. See invite here:

    • KD says:

      Thanks for your replies.

      I understand a specific price is not really feasible to quote, I’m more curious if the costs are exorbitant more than anything.

      • For a rough estimate, you can estimate $1 per gallon capacity for the size of the tanks and $4-$9 per linear foot for installed galvanized or aluminum gutters. Then there are a few other components such as downspouts and the technical equipment such as pumps and irrigation controllers. Hope this helps a little more.

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