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Earthship Systems: Water

Water. The elixir of life. Fresh drinking and washing water is something that so many people take for granted. In all first world countries, you can just turn on the tap and there it is! Water you can drink and wash with, and the supply seems to be endless. Wakeup call, that couldn’t be farther from the truth. The reality is many of the world’s fresh water aquifers are being depleted, and many others are being polluted. Not to mention that many people living in third world countries don’t even have access to fresh, clean water. The answer? Water from the sky. Here is the most thorough explanation of how an Earthship collects and uses water that I can muster, based on the past 8 months of my experiences with Earthship Biotecture. The key concept to understand about the Earthship water system is conservation. Just because we can catch a lot of rain water doesn’t mean we should squander it. Regardless of how much water an Earthship catches and stores, all water is used 4 times before it returns to the environment! Lets start at the beginning. We all know where rain comes from. If you don’t, you probably shouldn’t be reading this blog, but I’m not one to discriminate, so go ahead and read up on the Hydrologic Cycle.
The Hydrologic Cycle.

The Hydrologic Cycle.



So you’re sitting all comfortable in your Earthship and it’s a rainy day. While you may be cursing mother nature because the game got rained out, remind yourself that your Earthship is hard at work collecting rainwater that you need to survive. The entire surface area of the roof is sloped and covered with channeled Pro Panel metal sheeting. This routes all rainwater to the gutters and then into the cisterns using only gravity.
A good view of the north sloping roof and east <-> west sloping gutters.

A good view of the north sloping roof and east <-> west sloping gutters.

Detail of the gutter.

Detail of the gutter.

The cistern inputs before being buried.  The black plastic discs at the bottom are the actual cistern tops.

The cistern inputs before being buried. The black plastic discs at the bottom are the actual cistern tops.

Cistern overflow drain pipe.  If the cisterns reach maximum capacity, the overflow is drained outside the house.

Cistern overflow drain pipe. If the cisterns reach maximum capacity, the overflow is drained outside the house.

A view of the cistern inputs behind the roof.  The gutters drain into these inputs.  Notice the metal flap that comes off the roof and into the gutter to prevent water from splashing out of the gutter.

A view of the Baja Earthship's cistern inputs behind the roof. The gutters drain into these inputs. Notice the metal flap that comes off the roof and into the gutter to prevent water from splashing out of the gutter.

Detail of a cistern input.  The actual input is that metal mesh covered pipe in the middle.  I do not actually know why it is designed this way.

Detail of a cistern input. The actual input is that metal mesh covered pipe in the middle. I do not actually know why it is designed this way.

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Seth explains why Earthships use two cistern inputs. Something else to note is that each of these inputs feeds a pair of connected cisterns. There are four cistern tanks in total, paired in twos. Seth mentions that this was a new feature to accomodate the heavy amount of rain in Texas, however, we did the same setup in Baja where there is only eight inches of rain per year. My take on it is that dual inputs are good anywhere in case of a heavy downpour.

So now you have several cisterns filled with rainwater. The next step is to filter it into drinking water domestic water. The domestic water is used for washing in the sinks and shower. Earthship Biotecture has created a board that contains a series of filters and a pump that does this. They call it the Water Organization Module (WOM).
Earthship Biotecture's Water Organization Module (WOM).  This is what filters rainwater into drinking and washing water.

Earthship Biotecture's Water Organization Module (WOM). This is what filters rainwater into drinking and washing water.

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Amzi explains Earthship Biotecture's Water Organization Module (WOM).

The pressure tank for the water system.  The pump in the WOM keeps this tank between 30 and 50 psi.  This tank acts like a pressure buffer to provide consistant water pressure to the entire house with having to run the pump all time.

The pressure tank for the water system. The pump in the WOM keeps this tank between 30 and 50 psi. This tank acts like a pressure buffer to provide consistant water pressure to the entire house without having to run the pump all time.

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Amzi connecting the cistern outputs to the WOM

Drinking water is routed from the WOM to a designated faucet on all sinks. At this point, this water leaves the system. However, some or all of it returns when we get to the toilet (see below)! Cold domestic water is routed directly to all sinks, showers, washing machine and to the hot water tank. Earthships do not use a convention water heater, but they do use a hot water tank. Do not get the two confused as they are very different, although they look almost identical. A convention water heater is a glass lined tank of water with a electric heating element or gas burner at the bottom to heat the water. The hot water tank Earthships use is also a glass lined tank, but instead an electric or gas element, they have a coil of thin pipe at the bottom that is filled with a liquid called Glycol. This tank is part of the Solar Water Heating system. This system consists of a solar water heater panel, copper piping between the panel and the tank, a 12v pump that keeps the glycol circulating and a seperate electric solar panel that is dedicated to powering the pump. The water heater panel is mounted on the front face of the house next to the main electric solar panels. It consists of a piece of glass that faces the sun and concentrates that energy on a large coil of piping that the glycol is running through. Glycol can enter this coil cold and come out scolding hot. From the output of the panel, the glycol is then piped directly through the coil in the water heater tank and then right back up to the water heater panel again. Glycol is used because of its excellent ability to conduct and transfer heat and also because it does not freeze. The dedicated solar panel for the pump is mounted direct next to the water heater panel. There is no battery to store electricity so it only runs when the sun is out. When hot water is required, it runs out of the hot water tank and through a supplementary gas water heater before it reaches a faucet. The gas heater will heat the water up to temperature if it’s a little low and do nothing if it’s up to temp. This may be necessary on cloudy days or late at night after the water in the tank has cooled down.
The water heater tank and supplementary gas water heater.

The water heater tank and supplementary gas water heater.

What the supplementary gas water heater looks like under the cover.

What the supplementary gas water heater looks like under the cover.

Copper piping between the solar water heater panel and the hot water tank.

Copper piping between the solar water heater panel and the hot water tank.

Detail of some of the glycol piping for the solar water heater system and the 12v pump.

Detail of some of the glycol piping for the solar water heater system and the 12v pump.

That big panel is the solar water heater.  Oh yeah, that's Brian jumping off the roof of the Crockett, TX Earthship.

That big panel is the solar water heater. Oh yeah, that's Brian jumping off the roof of the Crockett, TX Earthship.

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Immediately following the completion of the water system, Ana executes the inaugural wash.

So now we know how cold and hot water make it from the sky to the faucet, but what happens after that? This is where the water begins to get re-used. Remember, the water in an Earthship is re-used four times before it’s returned to the environment. Used washing water is refered to as gray water and is routed through a reception cell which is a redwood box with a sheet of copper with holes in it to filter out large particles.
Gray water reception cell.

Gray water reception cell.

From there it goes directly into one end of the gray water planter botanical cells in the greenhouse where it is used to feed plants and gets naturally filtered and cleaned by them. The planter cells are approximately 4 feet deep, but slightly deeper on the far end to allow water to flow through them using gravity. At the bottom of the planters, there is a layer of medium sized rocks and then a layer of gravel on top of that. Then comes a layer of sand and then dirt where the plants are planted. There is a resevoir of gray water in the rock levels. It’s level is maintained by an overflow which goes straight into the septic system. The roots of the plants grow down and tap into this resevoir. Some of the water the plants absorb gets evaporated through their leaves and creates humidity in the house.
Digging out the gray water planter cells.

Digging out the gray water planter cells.

The planter cells underway.  Here you can see the EPDM rubber lining and the river rock layers which are used to maintain a water resevoir.

The planter cells underway. Here you can see the EPDM rubber lining and the river rock layers which are used to maintain a water resevoir.

Gray water planter cells completed.  The pipes sticking up are for obervation and access to see water level and access pumps.

Gray water planter cells completed. The pipes sticking up are for obervation and access to see water level and access pumps.

The pump that pulls water from the far end of the gray water planter cells and pushes it though that filter which then leads to the toilet.  Inside one of those tubes is the re-circulation pump.

The pump that pulls water from the far end of the gray water planter cells and pushes it though that filter which then leads to the toilet. Inside one of those tubes is the re-circulation pump.

The water that makes it to the end of the planter cells is either pumped out through a filter to the toilet or is re-circulated by a pump back to the beginning of the planter cells. The re-circulation exists so that water does not become stagnant.
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Amzi explains the pump and filter that send gray water to the toilets.

Which brings us to the toilet! To clarify, the toilet is the third use of the caught rain water. It has already been used for washing/drinking and watering all the plants in the greenhouse. If you remember earlier I mentioned that drinking water exits the system as soon as it leaves the drinking water faucet. Well, here is where some of that water returns to the system. Once you flush the toilet, the water is then referred to as black water. It goes straight into the septic tank.
Piping from the toilet leading to the septic system.

Piping from the toilet leading to the septic system.

Black water input from the toilet to the septic tank.

Black water input from the toilet to the septic tank.

The septic tank.  You can see the output pipe to the first black water planter cell.

The septic tank. You can see the output pipe to the first black water planter cell.

The septic tank is buried outside the front of the house. It has three chambers. Each chamber has a hole in the the bottom of the wall leading to the next chamber. How it works is, solid and liquid waste enter the first chamber, liquid waste immediately disperses evenly through all three chambers via the holes. Solid waste accumulates in the first chamber and floats. Over time the solid waste breaks down into liquid and will then disperse amongst the three cells. When the tank fills up, it then will exit the drain into the outside blackwater planter cells. Those cells are lined with EPDM rubber sheeting and then filled with rocks, sand and soil just like the inside greenhouse planters. Two thousand gallons of blackwater fills the bottom resevior of the planters and feeds the plants growing the in the cells above. Believe it or not, plants actually like black water! Plants thrive on nirates, and guess what, human waste is filled with nitrates! The cells are lined with rubber so no waste ever goes into the ground. The liquid to absorbed by plants and whatever is not used is evaporated by their leaves. The question, “Can you grow fruits and vegetables with black water?” is always asked and the short answer is yes (or at least Phil does). Logic and science say you can, but my stomach always seems to say no! However, I am willing to give it a shot!
A peek into the septic tank.  Don't worry, that's clean water!  Here you can see the walls that make up the three chambers.

A peek into the septic tank. Don't worry, that's clean water! Here you can see the walls that make up the three chambers.

The first of two black water planter cells.

The first of two black water planter cells.

Let’s reference the diagram of the Hydrologic Cycle at the top of this post. As you now know, sewage from the Earthship never penetrates the ground. So unlike most septic systems that output liquid overflow into a leech field and ultimately back down to the aquifer or even possibly runoff into a stream, Earthship sewage systems bypass the Earth completely. The cycle is limited to Precipitation -> Earthship use -> Transpiration. That’s how you turn desert into an oasis with no waste whatsoever. Booyah.
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Mike Reynolds gives an overview of the entire water system of an Earthship.

4 comments to Earthship Systems: Water

  • These are great, I want one so bad

  • Heya i?m for the first time here. I found this board and I in finding It truly helpful & it helped me out much. I’m hoping to give one thing back and help others such as you aided me.

  • I love your project , but I have one small question , can you use the black water to create some methane for cooking or heating , I think you can so probably the cistern of the black water needs a redesign , also I am not very sure that the human waste are good for the plants , I have read somewhere else that they are actually toxic , only animal waste is very good for the plants and the soil …., please tell us step bu step how much each parts costs you that way we can have an idea about the actual cost cause that what it boils down to for many people …keep the great job….

    • Yes! You totally can. I have seen some inexpensive systems that capture and process methane gas from sewage. I am interested in this but it is not part of the Earthship design. This could supplement or even replace the use of propane for supplemental water heating (never needed if dont take showers on rainy days or at 5am) and cooking gas.

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