With our current bad drought conditions it makes no sense to pour perfectly good water down the sewer. So we just joined the greywater underground with our illegal washing machine surge tank, and the installation was a piece of cake.
We built our washing machine surge tank based on the design in Art Ludwig’s book Create an Oasis with Greywater. The purpose of the surge tank is to prevent the built-in pump in the washing machine from burning out, which might happen if you tried to pump the water through pipes. The tank also slows down the flow of water going out to the garden, allowing more time for it to percolate into the soil. In addition the tank lets the water cool a bit, should we run a load in hot water.
For the tank we picked up a used and cleaned 55 gallon plastic drum with two “bung holes”, and plumbed it based on a design from Aquabarrel.com. The folks at Aquabarrel offer kits or a DIY video. We put our barrel together ourselves with a couple of common pvc fittings from the hardware store and omitted the overflow pipe, since our washing machine load will never exceed 55 gallons. The basic idea behind the Aquabarrel design is to turn the barrel upside down and use the preexisting threaded bung holes to connect up a garden hose. It took just a few minutes to complete, and our washing machine surge tank was ready to use. We highly recommend the Aquabarrel design, and you could combine a washing machine surge tank with a rain barrel with the addition of the overflow pipe and a fitting for the gutter.
When we do a load of laundry the waste water that collects in the barrel flows immediately out the garden hose and down towards the front slope of our little compound. Ludwig warns against keeping grewater around as it will quickly turn septic. We use Oasis Biocompatible detergent which is manufactured specifically for greywater systems. Regular “eco” detergents, while not harmful to aquatic plants, often contain substances that will kill terrestrial plants so you must use a greywater specific detergent.
Our next step will be to figure out some plantings that will take advantage of our laundry schedule, and to construct some simple earthworks and mulch basins to accommodate the water flow. Right now we just let the water percolate into the front slope, and our rosemary and Mexican sage look a lot healthier for it.