In the summer of 2001, my wife and I were designing our house with the goal of making it as green as possible. Naturally that meant using sustainable building practices and ensuring the house would be energy efficient, but we wanted to go further and include the plumbing system in our green design. Our local environmental health department responded positively when we inquired about the possibility of installing a composting toilet and greywater system, so we began researching our options.

Choosing the toilet was relatively easy (we went with the Phoenix R-200, www.compostingtoilet.com), but we found a wide range of potential greywater system designs. As with solar heating, greywater systems can be either active or passive. The former rely on pumps and filters, the latter on gravity. Active systems generally are more expensive, require more maintenance, and are more likely to be abandoned within a few years.

Our research led us to Oasis Design (www.oasisdesign.net) and Art Ludwig, who has been designing greywater systems since 1989. His three books, Create an Oasis with Greywater, Branched Drain Greywater Systems, and Builder’s Greywater Guide, provide a wealth of information. After weighing the options, we decided that the branched-drain system best combined the features we wanted and would allow us to acquire a system permit.

This branched-drain system is an update of the old “drain-out-back” greywater system. However, instead of simply having the greywater exit the house through a single pipe or hose, the branched-drain system carries the water through buried pipes that branch several times. A specially designed tee called a double ell, which is curved to split the flow evenly without clogging, accomplishes the branching.

In our system, the greywater exits the house and then goes into one of two branching networks, depending on which way the diverter valve is set. Having two separate zones allows each one to recharge during regular drying periods. In each zone, the greywater splits three times on its way to the eight outlets. At each successive junction, the water flow is halved, so that the final outlets release one-eighth of the total flow.

The outlets consist of five-gallon buckets, each of which has the bottom cut out and many holes drilled in the sides. Each bucket is buried in a mulch basin, an excavated ring filled with mulch. The greywater pipes enter the buckets, where the water falls at least six inches to the gravel-covered bottom. From there, the greywater penetrates into the mulch.

The outlets consist of five-gallon buckets, each of which has the bottom cut out and many holes drilled in the sides. Each bucket is buried in a mulch basin, an excavated ring filled with mulch. The greywater pipes enter the buckets, where the water falls at least six inches to the gravel-covered bottom. From there, the greywater penetrates into the mulch.

At the center of each mulch basin is a tree that will help soak up the water. We planted mayhaw trees (crataegus aestivalis), which produce a crabapple-like fruit, in the center of two basins, and cornelian cherry trees (cornus mas), related to dogwood, in the other two.

The system was relatively inexpensive and easy to assemble. The only hardware in the system is the diverter valve, pipes, joints, double ells and five-gallon buckets. The only difficult parts of the installation involved laying out the pipes so that they sloped enough (1/4" per foot) to maintain flow and leveling the double ells so that the flow would split evenly.

As I mentioned, our local environmental health department was receptive to the idea of a greywater system. Upon doing the research and deciding what kind of system to install, we wrote a detailed proposal for our permit application. In addition to system design, we included information about our site, greywater load estimates and surge capacity. The environmental health director had worked at the state level on greywater regulations, and he found our proposal to be adequate. He issued a permit with one stipulation: he required that we install a 500 gallon holding tank, so that he could avoid having to send our proposal to the state technical review board. Since we didn’t care to wait months for another evaluation that might or might not yield a favorable result, we agreed.

The story doesn’t end there, however. The house took longer than we expected to build, so we had to renew our permit after a year. Unfortunately, the environmental health director had moved to another county, and his replacement sent our proposal to the state review board. The state thereupon rejected our permit renewal, and we had to spend the following months negotiating with environmental health officials at the county, district and state levels. In the end, they gave us a permit for an experimental system, and required that we provide quarterly reports for the first three years. The benefit of going through all this trouble was that they let us build the system exactly as we originally proposed it, without the 500 gallon tank. (We preferred not to have the tank because anaerobic processes turn standing greywater into blackwater in about a day.) Although we had surmounted the permit challenges, we feared that our home lender Fannie Mae, would be unwilling to offer us a fair mortgage, given our home’s atypical features. In this case, everything fell right into place. Our banker asked Fannie Mae directly about the composting toilet and greywater system and was told that they were not a problem.

In five months of use, the greywater system has performed admirably. As for maintenance, we have only needed to switch the diverter valve every couple of weeks. We also have to be vigilant about keeping toxic chemicals out of the greywater plumbing system. Overall, we’re happy with the choices we made and the effect of those choices on the environment. We’re confident and pleased that our greywater system and composting toilet will not have a negative impact on surface and ground water, like typical systems may.

About the author: Dr. Allison A. Bailes III is currently on staff with Southface, view biography.