s part of my general obsession with lessening my impact on the land, I had read up on gray water reuse, but I had no practical use for my knowledge until my friend bought a house and started fixing it up to rent to vacationers. There, I saw the alignment of three circumstances that made my friend's backyard perfect for such a project. The yard was lined with trees -- fig, apple, pear, peach, plum, and persimmon -- that would all need watering through the rainless summer months. Unlike many other types of plants, fruit trees don't mind the mildly alkaline soil created by soapy gray water. The orchard was downhill from the house, so gravity was the only pump I needed. And all of the gray water from the second story fed into a single pipe before it joined the septic line, which made redirecting the water easy.
Before I lifted a shovel, I spent time pacing the yard, working out the details of the setup. Commercial gray water systems can get quite complicated, with pumps, filters, and surge tanks to temporarily hold excess flow. But filters clog and pumps break down. Ludwig's system is a marvel of simplicity. Water runs downhill through a series of forking pipes; at the end of each branch is an "infiltrator," an underground chamber filled with wood chips, set at the outskirts of a tree's root circle. A pocket of air at the top of each chamber provides oxygen for bacteria to devour any pathogens that may be present in the gray water. At the same time, the infiltrators are completely buried, so pets and children can't get at them.
The biggest puzzle was figuring out the maximum amount of water that could be flushed from the house at any given time. Using a chart from Ludwig's book, I added up the surge capability of all the sinks, showers, tub, and washer that would feed into the system, and came up with a ballpark figure of 75 gallons. The system I would install had to be able to handle at least that much water.
After all the head-scratching, actually assembling the system was fun. For the past few years I have made my living building decks, so I have at my disposal a small arsenal of tools and skills. But I didn't need many tools for this job -- a hacksaw, a jigsaw, a hole saw, and a level -- and the skills were basic for anyone with a modicum of handiness.
My first step was to install a diverter valve in the basement, so we could turn the system on and off with the twist of a handle. This would allow us to direct the flow into the septic tank if the gray water system needed to be serviced, or if the yard flooded during heavy rains. Ordinary plumbing-supply stores had no idea what I was talking about when I asked for one of these valves, but a pool supplier had one in stock. I found everything else at the hardware store -- plastic piping and fittings, five-gallon buckets -- with a few exceptions: I had to order flow splitters ("double ells," in plumbing parlance) and 55-gallon drums online.
We dug our trenches and fit our pipes together like Tinkertoys. The most challenging part of the operation was making sure the slope of the pipes was steep enough so that water would reach the infiltrators without pooling. I turned each bucket upside down and cut a hole in the bottom, creating a portal through which to monitor flow. A pile of flat stones provided me with all the manhole covers I needed.
After two days of digging and fitting we were ready for our big moment: We cranked all the faucets upstairs. What began under the house as a single river was broken down into eight rivulets, each of which was easily soaked up by the underground mulch chambers without a trace of puddling. I ran around the backyard, feeling the same rush I had felt as a kid after completing some streamside marvel of hydraulic engineering. Then we let flow the pale ale and turned the labor of backfilling the trenches into a victory party.
s any homeowner knows, there is nothing about a house that is actually "maintenance free," but over the course of its lifetime, our system should require minimal tweaking. Gray water can increase the pH of soil over time, but this condition can be offset with a little gypsum or elemental sulphur, two common soil additives readily available at nurseries (it's generally agreed that there's no reason not to use this stuff). My friend will have to do his best to police the system, to make sure no chlorine or borax or Drano gets washed downstream. He will also stock his kitchen and laundry room with the most benign detergents and cleaning products he can find.
We calculated that putting the system in place cost him $1,500, most of which went toward my labor and that of the three guys who helped us. Water is cheap in his neck of the woods: Over 20 years he will save about $500 in irrigation water. But a new septic system can cost $15,000, so the extra life that he will get out of the existing one is not negligible. Nor is the peace of mind in knowing that his tank won't overflow if he's got a house full of bath-crazy renters in for the weekend.
But if it were just about money we would have drunk the ale and saved ourselves all the trouble. The deeper satisfaction in a venture like this one comes in knowing we created something beautiful and nourishing from something most people are happy to be rid of. It may be a drop in the bucket, but there's a peach tree growing out of that bucket.