Water Reuse

(Page updated 12/04/07)

This page contains information about our current system of reusing "waste" water. For related information, see our webpage on Our Current Composting Toilet.

Most of our wastewater, except from the shower, is collected in a 5 gallon bucket and is then dumped into mulch basins around trees and shrubs immediately after collection. This is the simplest, most effective way we have found to treat and reuse our wastewater. By emptying wastewater into mulch filled basins where oxygen is plentiful and microbial activity is high, treatment levels for the wastewater are also high. Also, research shows that tree roots are very effective in the uptake of nitrogen, which is a wastewater component and a recognized groundwater contaminant. For these reasons, the treatment level of the water is probably higher than with most conventional systems such as septic or municipal wastewater treatment, despite the simplicity of the method.

This is a convenient method to use because our water supply system encourages radical water conservation, so there's not much wastewater to deal with. There is no drain plumbing anywhere in our wastewater system.  Nearly all of our water use is outdoors and we have no plumbing of any kind inside our dwelling.  Instead, located immediately outside the door is an open top stock tank into which water (from well, rainwater harvesting, etc.) enters.  Water is dipped out by bucket as needed. The water conservation principle is that as much water can be used as is desired, but every drop must be lifted from tank to point of use. For more details, see the Water Use page.

Mulch basins:

We use 7 mulch basins, one for each day of the week. Each basin located around a tree or bush and is about 5-6 feet in diameter and 10-12 inches deep. The basins are filled with mulch such as shredded leaves or wood chips. For convenience, the basins are located no more than about 25 feet from the water use area. In Arizona, the wastewater is absorbed by the roots of mesquite trees, thus helping to provide us with shade, firewood and edible pods. In Oregon, the water irrigates a holly bush and blackberries.

With our 15 gallon per day graywater/blackwater output, 7 mulch basins are ample to prevent soil plugging or anaerobic conditions. Wastewater is dumped into a different basin each day to allow time for insects, worms, bacteria, fungi and other agents of decomposition to break down the organic solids, oils, grease and soap. This system has worked well in all seasons and in silty as well as heavy clay soil.

Kitchen "black" water:

Dishes are washed outdoors in dish pans on a table next to the water supply tank. The waste water is then dumped into a 5 gallon bucket dedicated to that use and is immediately emptied into mulch basins as described above.   

Of all residential wastewater, that from the kitchen sink is typically the most problematic to reuse because it is relatively high in organic solids, oils, grease and soap which over time tend to seal up soil pores, preventing water from infiltrating the soil and resulting in a puddle of gray, smelly, anaerobic and potentially pathogenic water. For these reasons, most U.S. jurisdictions classify kitchen wastewater as blackwater.  "Graywater" refers to wastewater other sources such as shower, bathroom sink and washing machine.

The simple mulch basin method described above never becomes anaerobic because the amount of kitchen and other wastewater we produce is small and because the water is distributed to a different mulch basin each day, allowing time for soil organisms to process the impurities. 

Shower graywater:

Our shower in Arizona is outdoors and the one we use in Oregon is semi-outdoors. In both, water for showering is supplied from an elevated 5 gallon bucket equipped with a flexible hose, spray nozzle and valve (for more details see our Water Use page). The shower floor is slatted boards (in Arizona) and 16 inch square concrete patio blocks (in Oregon).  In both cases, the shower floor is located on top of 8x8x16 inch concrete blocks buried in the ground with the tops even with the soil surface. The blocks are installed with the cores vertical and the cores are filled with compost. 

The function of the blocks is to provide a sturdy base for the shower floor and to contain the compost. The function of the compost is to promote good drainage by filtering out soap, hair and other impurities before they reach the native soil.  In use, shower wastewater passes through the slatted floor or between the patio blocks and then through the compost and into the native soil. To prevent the compost from eventually plugging with soap scum, etc., it is replaced once or twice each year.  As with our mulch basin system, this one works well because of the limited amount of water that needs to be processed.

Lavatory sink graywater:

In lieu of a lavatory sink, we use a plastic wash basin on a table outdoors. The basin is emptied into the graywater bucket and is then dumped into a mulch basin as described above.

Laundry graywater: In Arizona and Oregon we now have access via neighbors to an energy and water conserving top loading washing machine.  Before, when we used the laundry method described on our Water Use page, we emptied the laundry tub into a mulch basin located next to the shower stand.  In Arizona, roots from nearby mesquite trees convert the graywater into shade, firewood and edible pods. In Oregon it is used to irrigate grapes.  

Wastewater quantities: These figures are our year-round averages for 2 people. Our water use is about the same whether we're in Arizona or Oregon:

-washing dishes - 5 gallons per day

-cooking, drinking and meal preparation - 2 gallons per day

-shaving, face washing, brushing teeth - 2 gallons per day

-showering - 4 gallons per day

-hand washing - 2 gallons per day

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