My First Simple Grey Water System

Since first publishing this article in the Blue Mountains Permaculture Newsletter 18months ago, and since actually starting the system over two years ago, I can confirm that it a) works well, and b) needs hardly any maintenance. More updates at the end.

My little grey-water system

OK, so its low technology, but it works and I’m proud of it! It re-uses up to 40litres of water a day, keeps a worm farm ticking over, grows mulch and waters a large vegetable bed. And it’s self regulating, low maintenance, and dare I say, reasonably presentable.

But it wasn;t always that way… I offer “The Short History Of My Grey Water System“ in the hope that it might be of use to someone, or even better, someone may be able to suggest an improvement!

My starting point was a dual-tub kitchen sink. Our kitchen habit is to use the larger sink for washing (hot soapy/greasy water) and the smaller tub for rinsing and washing vegetables (mostly clean, cold water). They had separate plug-holes but joined together underneath the sink to take the waste-water away to the sewer. For the first (and definitely not the last) time I thought “There must be a better way”.. I might also add that I had the benefit of having my kitchen above the level of my garden (thus permitting gravity to do the work of shifting the water to where it was needed), and easy underfloor access to change pipe-work around. I set myself the task of using this ready supply of relatively clean and cold water for the garden.

Grey-water system Mark 1 – I separated the drain-pipe of the small rinse sink from the main sink and let it empty into a bucket. A length of garden hose then carried the water to the garden bed where it dripped from holes periodically drilled into the hose. My reasoning was that this would allow any solids form the sink to fall to the bottom, preventing them from clogging up the hose-pipe. Unfortunately the residue in the water encouraged mould to form quickly in the bucket which clogged the hose-pipe. Added to that, emptying the residue from the bottom of the bucket was a fairly unpleasant task (to say the least). I said again “There has to be a better way”!

Grey-Water system Mark II. I modified Mark 1 by adding a garden sieve filled with gravel to sit on top of the bucket and catch any solids coming from the rinse-sink. This, I reasoned, would reduce the solids accumulating in the bucket and stop the mould growing. I also upgraded the drip pipe section of the system. Previously I had used old hose-pipe with holes drilled in it; this I now replaced with 19mm irrigation pipe, again with holes drilled (approx 5mm) into it. This I reasoned, would be less likely to clog. Unfortunately, Mark II lasted for a shorter time than Mark 1 – the gravel quickly became clogged with debris and turned out to be very difficult to clean. Added to this, the fact that the bucket was now enclosed meant that the anaerobic bacteria had an even better time with the nutrient laden water than before. The mould growing on the inside of the bucket now was something from the special effects department of a horror film! This was a grey-water system which could give grey-water systems a bad name!! I said again “There has to be a better way”

Grey-Water system Mark III. Going back to Permaculture basics I imagined Bill Mollison lecturing to me “the current problem manifesting as an excess of solid material in the waste water is actually caused by a shortage of worms”. This quickly led to the addition of a worm farm to remove the solids. The output pipe from the rinse sink now empties into a worm farm which uses pine bark granules as the base medium. The layers of slowly decaying bark catch any of the solids as the water passes through. The solids then become food for the aerobic composting bacteria which in turn become food for the worms. Hey-presto – the water draining from the bottom of the worm farm is now solid free – and I have a thriving worm farm fed by a constant supply of nutrients from the sink. This simple formula has been working now for three months and I havn’t yet had to clear out the worm farm. Excited by my success I said again, albeit in a slightly brighter tone, “There has to be a better way still”

Grey Water system Mark IV. Again I went back to permaculture basics, and the principle that every element in a design should have as many uses as possible. I reckoned I could clean the water even more, reduce the nutrient level even further, by passing the output of the worm farm through an intensive mulch growing bed. I currently have an old sink full of ginger lily (a terrifically drought, flood, heat and cold tolerant weed) fed by a constant supply of nutrient rich water. The ginger lily grows rampantly (within the confines of the sink!!) and the lush green growth will periodically be harvested for the compost heap. The excess water, which is always clear and clean now, drains from the bottom of this bed and onto my lettuce and spinach as before.

I have now paused to admire my creation working prior to asking how I could improve it again. Any suggestions?

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Believe it or not, I just replaced the pine bark chips for the first time last week. They had actually long gone, and the coco peat that I was adding had poor drainage qualities, so it was getting waterlogged. I have the old mulch tray sitting above the new one in the hope that the worms will make their own way down as the old one dries up. Once that happens I can harvest the rich worm casts for a new summer lettuce planter box for the patio. I also replaced some of the ginger lilly with canna for more diversity of flowers - ok I am becoming a bit of a sap to ornament in my old age!

This was a good project to start out on because it avoided dealing with the more dangerous parts of water recycling - the foecal coliforms that are present in shower (or even washing machine) water and which can be problematic if not dealt with properly.
Now onto bigger and better things!