From Sky to Earth: The Path of Water Through the Simple Survival Earthship
During the fall of 2015 I traveled to New Mexico, USA to attend the Earthship Biotecture Academy. This one-month program occurs 4 to 5 times a year on the campus of the Earthship Biotecture design and construction company in the high desert of Taos.
As is proclaimed on the Earthship website, “… the earthship is the epitome of sustainable design and construction. No part of sustainable living has been ignored in this ingenious building.” While I would say that there is always room for improvement, and that there is never a ‘right answer’ in architecture, the Earthship team has made some great breakthroughs in both the use of recycled materials and the reuse of grey-water for the domestic growth of food year-round. The academy session was a great experience, and I recommend it to anyone interested in off-grid housing.
Having learned of these strategies over the course of the one-month academy, I was then honored to be asked to return to Taos a few months after the session to assist the Earthship team in authoring graphics for a new version for the text book. Over the course of three months, I developed illustrations showing the path of water for domestic use, as well as a visual aids for effective use of recycled materials. (I also developed the new Earthship Academy Logo at right.)
To be honest, I’m not sure if the new textbook has been published or if it will be anytime soon. Regardless, I’ve felt that it’s important to get these graphics out into the public realm. In this blog post, I will outline the path of water in a “Simple Survival Earthship” – which is the most basic, least expensive design to have been developed by the Earthship team. A follow up post will cover a more sophisticated path of water for higher-end clients, and a third will cover construction methods employing recycled materials.
From Sky to Earth: The Path of Water in the Simple Survival Earthship
The Simple Survival is the smallest, most economical model developed by the Earthship team. While the roofing system and precise location of some elements may change, the plan consists of a studio-style living space with a washroom, water closet, and equator-facing greenhouse. The entire space is both excavated and surrounded by a retaining wall and earth berm that allows the space to harness the thermal energy of the Earth. Using a maximum surface area for the roof, all rainfall is captured and stored within subterranean tanks behind the retaining wall. This water is then filtered, consumed and used, recycled through grow beds of edible foods, used again, then disseminated out into the surrounding property to foster growth of landscaping and season food crops.
The first step of the process looks identical in almost all Earthships. While any standard gutter system could be used, on-site cut and formed gutters allow for a custom transition from gutter to storage. Alternative systems could be made from plastic or PVC. What is essential is to ensure that the water passes through a series of coarse filters. The current Earthship strategy includes a small dam at the end of the gutter, and gravel within a modified industrial sized perforated salad bowl (literally a salad bowl, as in cooking supply store, not hardware). The water then passes through an inverted toilet flange. This system must be bolted (with at least two bolts) to the water tank below.
Your choice of water tanks is essential. Not all water tanks can be buried. In fact most are designed for surface storage, and will rupture or otherwise deteriorate in subsurface conditions. Be sure that whatever tank you install is specified for being buried and will be placed on undisturbed/compacted earth. If you are burying more than one tank (project location and the number of occupants are determining factors) the connection between the two must be done with 2” flexible PVC pipe. The 2” is then reduced through a T to 1” semi-flexible pipe before entering the interior of the home. Everything viewed at right is buried below ground.
The supply side for the Simple Survival Earthship is exactly that: as simple as can be for survival. The tanks within the earth berm gravity feed a hose that can be used to fill up a bucket for washing or watering of plants. After passing through a minimal in-line filter, the supply must be pressurized through the installation of a pump of some kind. This can either be a hand pump or an electric pump that is either pressure-activated or turned on with a switch. If an electrical pump is used, a Power Organizing Module (POM), or small car battery hooked with standard outlets, must be connected. After passing through a hose manifold that would allow different attachments, the pressurized water can be stored in elevated black painted containers under daily sunshine. The solar gain from these canisters will supply semi-reliable hot water (depending on the location) in the afternoons.
After being used at the kitchen sink and in the shower, grey water moves to two adjacent planters that filter the water and provide growth media for both beautiful and edible flora. The depth and width of any planter is limited by the waterproofing containment material strategy. The Earthship team typically uses ethylene propylene diene terpolymer membrane (EPDM), which comes in rolls of 3 meter width. Each planter can therefore be only about 1 meter wide in order to achieve the needed depth to support plant life.
An effective planter must descend slightly along the path of water, ranging from 32 to 38 inches. Within this system, water must be circulated regularly.
Typically, a small sump pump is attached directly to a single solar panel that ensures water movement during daylight hours. Inspection chambers,
connection details and soil mixtures will be covered in a follow up blog post.
When it comes to “number 2” in a Simple Survival Earthship, it should first be acknowledged that if not built correctly, a toilet system can become a catastrophic mess. This is why typical septics and sanitation systems are developed in accordance with numerous building codes and regulations. It is also why the Simple Survival uses a design that has garnered the nickname of an “Outlaw Septic”. This system will not pass most septic regulatory inspections. It will, however, get the job done at minimal cost. Placed over a 5’6” diameter EPDM lined excavation, toilet flushes taken from the greywater planters are deposited into the center of a stack of large truck tires. The solids eventually break down and seep through the cracks between the tire treads. Further filtered through large rocks, the liquid overflows into an external grow bed that further breaks down the refuse. In this external grow bed, the black water is evaporated, consumed through ecological transpiration, and put to use in providing life in giving nutrients to our surrounding landscape.
This is the most basic path of water employed by the most “bare bones” Earthship design. When designed and used effectively, a single person’s water consumption can be reduced by more than 50%. As mentioned however, some of the steps here pose problems when building within a formal, law-abiding context. I will address this in a follow-up post outlining that path of water for the “Global Model” (perhaps explained as a “deluxe model” Earthship). The next post will cover systems of filtration, circulation, and the incorporation of more standard design details.
Thanks for reading – I hope this has been helpful. Feel free to drop a comment below with questions that I can use to develop the next post!