December 2012: Rainwater Catchment Options for the Urban Prefab Home

Greenbuild 2012 Showcases 5,000 Gallon Water Tank

Image via Inhabitat

“I was curious to see the show house at Greenbuild 2012 demonstrating a large, above-ground, steel riveted water tank,” writes HOG inventor, Sally Dominguez.  “In a seismic high risk area like San Francisco riveted steel tanks are not recommended – in fact most manufacturers will not supply them to parts of California – because in a moderate seismic event a small amount of movement is enough to twist the structure and pop the rivets – and any movement could send tons of water rolling! Did I mention that HOG tanks can’t roll?!”

Inhabitat writer Charley Cameron reports, “The water management for the Paradigm house has several levels; rainwater is diverted from the home’s roof to a 5,000 gallon free-standing outdoor tank, from which water is filtered for domestic use. Greywater is then collected for irrigation and fed directly to two small outdoor greenhouses where produce can be grown. The home’s compost toilet could potentially provide fertilizer for this on-site veggie patch.”

Sally responds, “What I find curious about an otherwise really tight, economical design is the size of the tank.  A 700 sq ft roof can only yield 436 gallons for every inch of rain, so for six months of the year in San Francisco the tank sits nearly empty; in March, our statistically highest rainfall month, it’s just under half full. A tank significantly smaller would still fulfill the water needs of a single bedroom house, especially one with a composting toilet.  It seems to be a case of seeking the largest storage without actually reckoning for local climate and household use.”

Simpatico Homes features Modular HOG System

Simpatico Homes rooftop

Image via Simpatico Homes

This month’s issue of Dwell magazine asks the the question, “Why prefab?” Simpatico Homes, a modular home company based in Emeryville, California, helps answer the question.  Although both homes have net zero energy as their goal, Simpatico Homes has a very different approach to rainwater harvesting than Method Homes’ Paradigm house. In a profile of the Simpatico Prototype House which founder Seth Krubiner now calls home, Joanne Furio reports, “Instead of taxing the taps, the home’s drought-tolerant garden can be watered with runoff from the roof. Krubiner’s technology of choice: Rainwater HOG, an off-the-shelf, expandable system of rainwater collection tanks that stores water for irrigation. Because the HOGs are slim, they can be positioned directly under a downspout without blocking the walkway – a necessity on a tight city lot like this. “The nice thing is that you can easily link them together,” says Krubiner… [who has] two sets of five 50-gallon HOGs…for the property.”

For more on the HOG tank’s unique design that prizes a small footprint and flexible, modular installation options for urban rainwater storage, check out the Rainwater HOG profile in AIArchitect’s online magazine.